Definition of the concepts "infection", "invasion", "infectious process", "infectious disease".

Infection - infection of living organisms with bacteria or viruses, or fungi, or protozoa. In medicine, the term infection means various types of interaction of foreign microorganisms with the human body and animals.

Types of infections

The infection can develop in different directions and take different forms. The form of infection development depends on the ratio of the pathogenicity of the microorganism, the factors of protection of the macroorganism from infection and environmental factors.

Local infection - local damage to body tissues under the influence of pathogenic factors of a microorganism. A local process, as a rule, occurs at the site of penetration of the microbe into the tissues and is usually characterized by the development of a local inflammatory reaction. Local infections are represented by tonsillitis, boils, diphtheria, erysipelas, etc. In some cases, a local infection can turn into a general one.

General infection - the penetration of microorganisms into the blood and spread them throughout the body. Having penetrated into the tissues of the body, the microbe multiplies at the site of penetration, and then penetrates into the blood. This mechanism of development is typical for influenza, salmonellosis, typhus, syphilis, some forms of tuberculosis, viral hepatitis, etc.

Latent infection - a condition in which a microorganism that lives and multiplies in the tissues of the body does not cause any symptoms (chronic form of gonorrhea, chronic salmonellosis, etc.)

Invasion (from lat.invasio - invasion, attack) is an ambiguous biological term.

2) diseases caused by pathogens - animals (for example, helminthic invasions - helminthiases) or protists (protozoal invasions - malaria, leishmaniasis, etc.). Diseases caused by protists are often referred to as infections.

In oncology, invasion is the ability of cancer cells to separate from it and penetrate into surrounding tissues. Thus, the ability to invade is a necessary condition for tumor metastasis.

In zoology, botany, ecology and biogeography, invasion is often called the introduction of new species into territories where they were previously absent, which occurs (unlike introduction) without conscious human participation.

In psychology, invasion is a condition in which the unconscious dominates the psyche of a healthy person (according to C.G. Jung).

infectious process - a complex multicomponent process of dynamic interaction of infectious pathogenic agents with a macroorganism, characterized by the development of a complex of typical pathological reactions, systemic functional changes, hormonal status disorders, specific immunological defense mechanisms and nonspecific resistance factors.

The infectious process is the basis for the development of infectious diseases. The practical significance of knowing the etiology and pathogenesis of infectious diseases, the general patterns of their development is due to the fact that infectious diseases for a long time occupy the third place in prevalence after diseases of the cardiovascular system and oncological pathology.

infectious diseases - This is a group of diseases caused by the penetration of pathogenic (pathogenic) microorganisms into the body. In order for a pathogenic microbe to cause an infectious disease, it must have virulence, that is, the ability to overcome the body's resistance and exhibit a toxic effect. Some pathogenic agents cause poisoning of the body by the exotoxins they secrete during their vital activity (tetanus, diphtheria), others release toxins (endotoxins) when their bodies are destroyed (cholera, typhoid fever).

One of the features of infectious diseases is the presence of an incubation period, that is, the period from the time of infection to the appearance of the first signs. The duration of this period depends on the method of infection and the type of pathogen and can last from several hours to several years (the latter is rare). The place of penetration of microorganisms into the body is called the entrance gate of infection. Each type of disease has its own entrance gate, for example, Vibrio cholerae enters the body through the mouth and is not able to penetrate the skin. Contents

1 Classification

2 Prevention

3 Literature

Classification

There are many classifications of infectious diseases. The most widely used classification of infectious diseases by L. V. Gromashevsky:

intestinal (cholera, dysentery, salmonellosis, escherichiosis);

respiratory tract (influenza, adenovirus infection, whooping cough, measles, chicken pox);

"blood" (malaria, HIV infection);

outer covers (anthrax);

with various transmission mechanisms (enterovirus infection).

Depending on the nature of pathogens, infectious diseases are classified into:

prion (Creutzfeldt-Jakob disease, kuru, fatal familial insomnia);

viral (influenza, parainfluenza, measles, viral hepatitis, HIV infection, cytomegalovirus infection, meningitis);

bacterial (plague, cholera, dysentery, salmonellosis, streptococcal, staphylococcal infections, meningitis);

protozoan (malaria, amoebiasis, balantidiasis, toxoplasmosis);

fungal infections, or mycoses (epidermophytosis, candidiasis, cryptococcosis, aspergillosis, mucormycosis, chromomycosis).

Preventive measures:

preventive vaccinations

quarantine measures

cure the source of the infection.

Quarantine is a set of measures to stop the spread of infection, this includes the isolation of previously sick people, disinfection of the place of residence, identification of those in contact with patients, etc.

Definition of the concept "Infection-infectious process"

Infection, infectious process (Late Latin infectio - infection, from Latin inficio - I bring something harmful, I infect), the state of infection of the body; an evolutionary complex of biological reactions arising from the interaction of an animal organism and an infectious agent. The dynamics of this interaction is called the infectious process. There are several types of infections. A pronounced form of infection is an infectious disease with a specific clinical picture (obvious infection). In the absence of clinical manifestations of infection, it is called latent (asymptomatic, latent, inapparent). The consequence of a latent infection may be the development of immunity, which is characteristic of the so-called immunizing subinfection. A peculiar form of infections is microcarriage unrelated to the previous illness.

If the route of entry of microbes into the body is not established, the infection is called cryptogenic. Often, pathogenic microbes initially multiply only at the site of introduction, causing an inflammatory process (primary affect). If inflammatory and dystrophic

changes develop in a limited area, in the place where the pathogen is localized, is called focal (focal), and when microbes are retained in the lymph nodes that control a certain area, it is called regional. With the spread of microbes in the body, a generalized infection develops. The condition in which microbes from the primary focus enter the bloodstream, but do not multiply in the blood, but are only transported to various organs, is called bacteremia. In a number of diseases (anthrax, pasteurellosis, etc.), septicemia develops: microbes multiply in the blood and penetrate into all organs and tissues, causing inflammatory and degenerative processes there. If the pathogen, spreading from the primary lesion through the lymphatic tract and hematogenously, causes the formation of secondary purulent foci (metastases) in various organs, they speak of pyemia. The combination of septicemia and pyemia is called septicopyemia. The condition in which pathogens multiply only at the site of introduction, and their exotoxins have a pathogenic effect, is called toxemia (characteristic of tetanus).

Infection can be spontaneous (natural) or experimental (artificial). Spontaneous occurs in natural conditions when the transmission mechanism inherent in this pathogenic microbe is realized, or when conditionally pathogenic microorganisms that live in the animal's body are activated (endogenous infection, or autoinfection). If a specific pathogen enters the body from the environment, they speak of an exogenous infection. An infection caused by one type of pathogen is called simple (monoinfection), and due to the association of microbes that have invaded the body, it is called associative. In such cases, synergism is sometimes manifested - an increase in the pathogenicity of one type of microbe under the influence of another. With the simultaneous course of two different diseases (for example, tuberculosis and brucellosis), the infection is called mixed. A secondary (secondary) infection is also known, which develops against the background of any primary (main), as a result of the activation of conditionally pathogenic microbes. If, after the transfer of the disease and the release of the animal's body from its pathogen, a re-disease occurs due to infection with the same pathogenic microbe, they speak of reinfection. The condition for its development is the preservation of susceptibility to this pathogen. Superinfection is also noted - a consequence of a new (repeated) infection that occurred against the background of an already developing disease caused by the same pathogenic microbe. The return of the disease, the reappearance of its symptoms after the onset of clinical recovery is called a relapse. It occurs when the animal's resistance is weakened and the causative agents of the disease that have survived in the body are activated. Relapses are characteristic of diseases in which insufficiently strong immunity is formed (for example, infectious anemia of horses).

Complete feeding of animals, optimal conditions for their maintenance and operation are factors that prevent the occurrence of infections. Factors that weaken the body, act exactly the opposite. With general and protein starvation, for example, the synthesis of immunoglobulins decreases, the activity of phagocytes decreases. An excess of protein in the diet leads to acidosis and a decrease in blood bactericidal activity. With a lack of minerals, water metabolism and digestion processes are disturbed, and the neutralization of toxic substances is difficult. With hypovitaminosis, the barrier functions of the skin and mucous membranes are weakened, and the bactericidal activity of the blood decreases. Cooling leads to a decrease in the activity of phagocytes, the development of leukopenia, and a weakening of the barrier functions of the mucous membranes of the upper respiratory tract. When the body overheats, conditionally pathogenic intestinal microflora is activated, the permeability of the intestinal wall for microbes increases. Under the influence of certain doses of ionizing radiation, all the protective-barrier functions of the body are weakened. This contributes to both autoinfection and the penetration of microorganisms from the outside. For the development of infections, typological features and the state of the nervous system, the state of the endocrine system and RES, and the level of metabolism are important. Breeds of animals are known that are resistant to certain I., the possibility of selecting resistant lines has been proven, and there is evidence of the influence of the type of nervous activity on the manifestation of infectious diseases. A decrease in the reactivity of the body with deep inhibition of the central nervous system has been proven. This explains the sluggish, often asymptomatic course of many diseases in animals during hibernation. Immunological reactivity depends on the age of the animals. In young animals, the permeability of the skin and mucous membranes is higher, inflammatory reactions and the adsorption capacity of RES elements, as well as protective humoral factors, are less pronounced. All this favors the development of specific infections in young animals caused by conditionally pathogenic microbes. However, young animals have developed a cellular protective function. The immunological reactivity of farm animals usually increases in the summer (if overheating is ruled out).

INFECTIOUS PROCESS AND INFECTIOUS DISEASES

The penetration of microorganisms into the internal environment of the human body leads to a violation of the homeostasis of the body, which can manifest itself as a complex of physiological (adaptive) and pathological reactions known as infectious process, or infection. The range of these reactions is quite wide, its extreme poles are clinically pronounced lesions and asymptomatic circulation. The term "infection" (from lat. infection- to introduce something harmful and late late. infection- infection) can determine both the infectious agent itself and the fact of its entry into the body, but it is more correct to use this term to refer to the entire set of reactions between the pathogen and the host.

According to I.I. Mechnikov, "... infection is a struggle between two organisms." Domestic virologist V.D. Solovyov considered the infectious process as "a special kind of ecological explosion with a sharp increase in the interspecific struggle between the host organism and the pathogenic bacteria that have invaded it." Famous infectious disease specialists A.F. Bilibin and G.P. Rudnev (1962) defined it as a complex set of "physiological protective and pathological reactions that occur under certain environmental conditions in response to the action of pathogenic microbes."

The modern scientific definition of the infectious process was given by V.I. Pokrovsky: "The infectious process is a complex of mutual adaptive reactions in response to the introduction and reproduction of a pathogenic microorganism in a macroorganism, aimed at restoring disturbed homeostasis and biological balance with the environment."

Thus, the participants in the infectious process are the microorganism that causes the disease, the host organism (human or animal) and certain, including social, environmental conditions.

Microorganism represents the immediate cause of an infectious disease, determines the specificity of its clinical manifestations, affects the course and outcome of the disease. Its main specific qualities:

pathogenicity;

Virulence;

Toxigenicity;

adhesiveness;

Pathogenicity - the ability of the pathogen to penetrate into the human or animal body, live and multiply in it, causing morphological and functional

The toxigenicity of the pathogen is the ability to synthesize and secrete exo- and endotoxins. Exotoxins are proteins secreted by microorganisms in the process of life. They exhibit a specific effect, leading to selective pathomorphological and pathophysiological disorders in organs and tissues (causative agents of diphtheria, tetanus, botulism, cholera, etc.). Endotoxins are released after the death and destruction of the microbial cell. Bacterial endotoxins are structural components of the outer membrane of almost all gram-negative microorganisms, biochemically representing a lipopolysaccharide complex (LPS complex). Structural and functional analysis of the LPS complex molecule showed that lipid A is the biologically active site (site) that determines all the main properties of the native LPS complex preparation. It is characterized by pronounced heterogeneity, which allows the body's defenses to recognize it. The action of endotoxins is not specific, which is manifested by similar clinical signs of the disease.

Adhesiveness and invasiveness of microorganisms - the ability to be fixed on cell membranes and penetrate into cells and tissues. These processes are facilitated by ligand-receptor structures and capsules of pathogens that prevent absorption by phagocytes, as well as flagella and enzymes that damage cell membranes.

One of the most important mechanisms for the preservation of the pathogen in the host organism is microbial persistence, which consists in the formation of atypical wallless forms of the microorganism - L-forms, or filterable forms. At the same time, a sharp restructuring of metabolic processes is observed, expressed in a slowdown or complete loss of enzymatic functions, inability to grow on elective nutrient media for the original cellular structures, and loss of sensitivity to antibiotics.

Virulence is a qualitative manifestation of pathogenicity. The sign is unstable; in the same strain of the pathogen, it can change during the infectious process, including under the influence of antimicrobial treatment. With certain features of the macroorganism (immunodeficiency, violation of barrier defense mechanisms) and environmental conditions, opportunistic microorganisms and even saprophytes can become the culprits for the development of an infectious disease.

The place of introduction of a pathogenic pathogen into the human body is called the entrance gate of infection; the clinical picture of the disease often depends on their localization. The properties of the microorganism and the route of its transmission determine the variety of entrance gates.

They may be:

Skin (for example, for causative agents of typhus, plague, anthrax, malaria);

Mucous membranes of the respiratory tract (in particular, for the influenza virus and meningococcus);

Gastrointestinal tract (for example, for pathogens of typhoid fever, dysentery);

Genital organs (for pathogens of syphilis, HIV infection, gonorrhea).

In various infectious diseases, there may be one (cholera, influenza) or several (brucellosis, tularemia, plague) entrance gates. The formation of the infectious process and the severity of the clinical manifestations of an infectious disease are significantly affected by the infectious dose of pathogens.

From the entrance gate, the pathogen can disseminate mainly by the lymphogenous or hematogenous route.

When a pathogen is found in the blood and lymph, the following terms are used:

-bacteremia(presence of bacteria in the blood);

-fungemia(presence of fungi in the blood);

-viremia(viruses in the blood);

The circulation of microbial toxins is defined by the term toxinemia. In some infectious diseases, bacteremia and toxinemia are observed simultaneously (for example, in typhoid fever, meningococcal infection), in others, toxemia develops predominantly (dysentery, diphtheria, botulism, tetanus). Disseminating in the human body, pathogens can affect various systems, organs, tissues, and even certain types of cells, i.e. show a certain selectivity, tropism. For example, influenza viruses are tropic to the epithelium of the respiratory tract, pathogens of dysentery - to the intestinal epithelium, malaria - to erythrocytes.

A macroorganism is an active participant in the infectious process, which determines the possibility of its occurrence, the form of manifestation, severity, duration and outcome. The human body has a variety of congenital or individually acquired factors of protection against the aggression of a pathogenic agent. The protective factors of the macroorganism help to prevent an infectious disease, and if it develops, to overcome the infectious process. They are divided into non-specific and specific.

Nonspecific protective factors are very numerous and diverse in terms of the mechanisms of antimicrobial action. External mechanical barriers

ramie for most microorganisms are intact skin and mucous membranes.

The protective properties of the skin and mucous membranes provide:

Lysozyme;

Secrets of the sebaceous and sweat glands;

Secretory IgA;

phagocytic cells;

Normal microflora that prevents intervention and colonization of the skin and mucous membranes by pathogenic microorganisms.

An extremely important barrier in intestinal infections is the acidic environment of the stomach. The mechanical removal of pathogens from the body is facilitated by the cilia of the respiratory epithelium and the motility of the small and large intestines. The blood-brain barrier serves as a powerful internal barrier to the penetration of microorganisms into the CNS.

Nonspecific inhibitors of microorganisms include enzymes of the gastrointestinal tract, blood and other body fluids (bacteriolysins, lysozyme, properdin, hydrolases, etc.), as well as many biologically active substances [IFN, lymphokines, prostaglandins (PG), etc.].

Following external barriers, phagocytic cells and the complement system constitute universal forms of macroorganism protection. They serve as links between non-specific protective factors and specific immune responses. Phagocytes, represented by granulocytes and cells of the macrophage-monocyte system, not only absorb and destroy microorganisms, but also present microbial antigens to immunocompetent cells, initiating an immune response. Components of the complement system, attaching to AT molecules, provide their lysing effect on cells containing the corresponding Ag.

The most important mechanism for protecting a macroorganism from the effects of a pathogenic pathogen is the formation of immunity as a complex of humoral and cellular reactions that determine the immune response. Immunity determines the course and outcome of the infectious process, serving as one of the leading mechanisms that maintain the homeostasis of the human body.

Humoral reactions are due to the activity of antibodies synthesized in response to the penetration of Ag.

AT are represented by immunoglobulins of various classes:

-IgM;

-IgG;

-IgA;

-IgD;

-IgE.

In the earliest stage of the immune response, the first to form are IgM as phylogenetically the most ancient. They are active against many bacteria, especially in agglutination (RA) and lysis reactions. Significant credits IgG appear on the 7-8th day after the action of the antigenic stimulus. However, with repeated exposure to Ag, they are formed already on the 2-3rd day, which is due to the formation of immunological memory cells in the dynamics of the primary immune response. In the secondary immune response, the titer IgG greatly exceeds the titer IgM. In the form of monomers IgA circulate in the blood and tissue fluids, but dimers are of particular importance IgA, responsible for immune

reactions on the mucous membranes, where they neutralize microorganisms and their toxins. Therefore, they are also called secretory AT, since they are mainly found not in blood serum, but in the secrets of the gastrointestinal tract, respiratory and genital tracts. They play a particularly important role in intestinal infections and SARS. Protective functions IgD and IgE not fully explored. It is known that IgE involved in the development of allergic reactions.

The specificity of antibodies is due to their strict correspondence with the Ag of the pathogen that caused their formation, and interaction with them. However, antibodies can also react with antigens of other microorganisms that have a similar antigenic structure (common antigenic determinants).

In contrast to humoral reactions, which are realized through antibodies circulating in the body, cellular immune responses are realized through the direct participation of immunocompetent cells.

Regulation of the immune response is carried out at the genetic level (genes of immunoreactivity).

Environment how the 3rd component of the infectious process affects its occurrence and the nature of the course, affecting both the micro- and the macroorganism. Temperature, humidity and dustiness of the air, solar radiation, antagonism of microorganisms and other numerous natural environmental factors determine the viability of pathogenic pathogens and affect the reactivity of the macroorganism, reducing its resistance to many infections.

The social factors of the external environment that affect the development of the infectious process are extremely important:

Deterioration of the ecological situation and living conditions of the population;

Malnutrition;

Stressful situations in connection with socio-economic and military conflicts;

health status;

Availability of qualified medical care, etc. Forms of the infectious process may be different depending on

properties of the pathogen, conditions of infection and the initial state of the macroorganism. Until now, not all of them have been sufficiently studied and clearly characterized. The main forms of the infectious process can be presented in the form of the following table (Table 2-1).

Table 2-1. The main forms of the infectious process

Transient(asymptomatic, healthy) carriage- a single (accidental) detection in the human body of a pathogenic (or any other) microorganism in tissues that are considered sterile (for example, in the blood). The fact of transient carriage is determined in a series of successive ba-

teriological analyses. At the same time, the currently existing examination methods do not allow to identify clinical, pathological and laboratory signs of the disease.

The carriage of pathogenic microorganisms is possible at the stage of recovery from an infectious disease (convalescent carriage). It is characteristic of a number of viral and bacterial infections. Depending on the duration, convalescent carriage is divided into acute(up to 3 months after clinical recovery) and chronic(over 3 months). In these cases, carriage is asymptomatic or occasionally manifests itself at the subclinical level, but may be accompanied by the formation of functional and morphological changes in the body, the development of immune responses.

Inapparent infection- one of the forms of the infectious process, characterized by the absence of clinical manifestations of the disease, but accompanied by an increase in the titers of specific antibodies as a result of the development of immune reactions to the pathogen antigen.

Manifest Forms infectious process constitute a vast group of infectious diseases caused by exposure to the human body of various microorganisms - bacteria, viruses, protozoa and fungi. For the development of an infectious disease, it is not enough just to introduce a pathogenic pathogen into the human body. The macroorganism must be susceptible to this infection, respond to the pathogen with the development of pathophysiological, morphological, protective, adaptive and compensatory reactions that determine the clinical and other manifestations of the disease. At the same time, the micro- and macroorganism interact in certain, including socio-economic, environmental conditions that inevitably affect the course of an infectious disease.

The division of diseases into infectious and non-infectious is rather conditional.

Basically, it is traditionally based on two criteria characteristic of the infectious process:

the presence of a pathogen;

Contagiousness (contagiousness) of the disease.

But at the same time, a mandatory combination of these criteria is not always observed. For example, the causative agent of erysipelas - group A β-hemolytic streptococcus - also causes the development of non-contagious glomerulonephritis, dermatitis, rheumatic process and other diseases, and erysipelas itself, as one of the forms of streptococcal infection, is considered practically non-contagious. Therefore, the treatment of infectious diseases is faced not only by infectious disease specialists, but also by representatives of almost all clinical specialties. Apparently, most human diseases could be classified as infectious. The creation of an infectious disease service, historically established as a result of the development of specialization in medicine, is intended to provide qualified assistance to infectious patients at the pre-hospital (at home), hospital (in a hospital) and dispensary (observation after discharge from a hospital) stages.

The nature, activity and duration of the clinical manifestations of an infectious disease, which determine the degree of its severity, can be extremely diverse.

With a typical overt infection, the clinical signs and general features characteristic of an infectious disease are clearly expressed:

The sequence of changing periods;

The possibility of developing exacerbations, relapses and complications, acute, fulminant (fulminant), protracted and chronic forms;

Formation of immunity.

The severity of overt infections can be different:

Easy;

Middle;

heavy.

A specific form of disease known as slow infections, cause prions.

They are characterized by:

Many months or even many years of incubation period;

Slow but steadily progressive course;

A complex of peculiar lesions of individual organs and systems;

Development of oncological pathology;

Inevitable death.

Atypical overt infections can proceed as erased, latent and mixed infections. An erased (subclinical) infection is a variant of the manifest form, in which the clinical signs of the disease and the change in its periods are not clearly expressed, often minimally, and the immunological reactions are incomplete. Diagnosis of an erased infection causes significant difficulties, which contributes to the prolongation of an infectious disease due to the lack of timely full-fledged treatment.

Perhaps the simultaneous occurrence of two infectious diseases caused by different pathogens. In such cases, they speak of a mixed infection, or mixed infection.

The development of an infectious disease may be due to the dissemination of pathogenic pathogens that were previously in the human body in the form of a dormant latent focus of infection, or the activation of opportunistic and even normal flora inhabiting the skin and mucous membranes. Such diseases are known as endogenous infections(autoinfection).

As a rule, they develop against the background of immunodeficiencies associated with a variety of reasons:

Severe somatic diseases;

Surgical interventions;

The use of toxic medicinal compounds, radiation and hormonal treatment;

HIV infection.

It is possible to re-infect with the same pathogen with the subsequent development of the disease (usually in a manifest form). If such infection occurred after the end of the primary infectious process, it is defined as reinfection. From reinfections and, especially, mixed infections should be distinguished superinfection, arising from infection with a new infectious agent against the background of an already existing infectious disease.

GENERAL FEATURES OF INFECTIOUS DISEASES

The generally accepted term "infectious diseases" was introduced by the German physician Christoph Wilhelm Hufeland.

The main signs of infectious diseases:

Specific pathogen as the immediate cause of the disease;

Contagiousness (infectiousness) or the occurrence of several (many) diseases caused by a common source of infection;

Quite often tendency to wide epidemic distribution;

Cyclicity of the course (successive change of periods of the disease);

The possibility of developing exacerbations and relapses, protracted and chronic forms;

Development of immune responses to pathogen antigen;

The possibility of developing carriage of the pathogen. pathogens

Specific causative agents of infectious diseases can be:

bacteria;

Rickettsia;

Chlamydia;

Mycoplasmas;

Mushrooms;

Viruses;

Prions.

The higher the contagiousness of the disease, the greater its propensity for widespread epidemic spread. Diseases with the most pronounced contagiousness, characterized by a severe course and high mortality, are combined into a group of especially dangerous infections.

Such diseases include:

Plague;

cholera;

yellow fever;

Lassa fever, Ebola, Marburg.

Cyclic flow common to most infectious diseases. It is expressed in the successive change of certain periods of the disease:

Incubation (hidden);

Prodromal (initial);

The period of the main manifestations (height of the disease);

Fading of symptoms (early convalescence);

Recovery (reconvalescence).

Incubation period

A hidden period of time between the moment of infection (penetration of the pathogen into the body) and the appearance of the first clinical symptoms of the disease. The duration of the incubation period is different for different infections and even for individual patients with the same infectious disease.

The duration of this period depends on:

From the virulence of the pathogen and its infectious dose;

Localization of entrance gates;

The state of the human body before the disease, its immune status.

Determining the terms of quarantine, carrying out preventive measures and solving many other epidemiological issues are carried out taking into account the duration of the incubation period of an infectious disease.

Prodromal (initial) period

The disease usually lasts no more than 1-2 days, it is not observed in all infections.

In the prodromal period, the clinical signs of the disease do not have clear specific manifestations and are often the same in different diseases:

Increase in body temperature;

Headache;

Myalgia;

arthralgia;

Malaise;

Brokenness;

Decreased appetite, etc.

The period of the main manifestations (height) of the disease

This period is characterized by the appearance and (often) an increase in the most characteristic clinical and laboratory signs specific to a particular infectious disease. The degree of their severity is maximum in manifest forms of infection.

By assessing these signs, you can:

Make the correct diagnosis;

Assess the severity of the disease;

Assume the nearest forecast;

Prevent the development of emergency conditions.

The different diagnostic significance of the symptoms allows us to subdivide them into decisive, supporting and suggestive.

. Decisive Symptoms characteristic specifically for a specific infectious disease (for example, Filatov-Koplik-Belsky spots in measles, hemorrhagic stellate rash with elements of necrosis in meningococcemia).

. Supporting symptoms are typical for this disease, but they can also be found in some others (jaundice in viral hepatitis, meningeal symptoms in meningitis, etc.).

. Suggestive symptoms less specific and similar in a number of infectious diseases (fever, headache, chills, etc.).

The period of extinction of symptoms (early convalescence)

Follows the peak period with a favorable course of an infectious disease. It is characterized by the gradual disappearance of the main symptoms.

One of its first manifestations is a decrease in body temperature. It can happen quickly, over a few hours (crisis), or gradually, over several days of illness (lysis).

The period of recovery (reconvalescence)

It develops after the extinction of the main clinical symptoms. Clinical recovery almost always occurs before the morphological disorders caused by the disease completely disappear.

In each case, the duration of the last two periods of an infectious disease is different, which depends on many reasons:

Forms of the disease and its severity;

The effectiveness of the treatment;

Features of the immunological response of the patient's body, etc.

With complete recovery, all functions impaired due to an infectious disease are restored, with incomplete recovery, certain residual effects remain.

In many infectious diseases, there is also the possibility of developing exacerbations and relapses, protracted and chronic forms. The causes of these conditions are varied and not well understood.

They may be associated with the specific features of all three components of the infectious process:

Pathogen;

macroorganism;

environmental conditions.

For each patient, the course of an infectious disease has individual characteristics.

They may be due to:

The previous physiological state of the most important organs and systems (premorbid background) of the patient;

The nature of the food;

Features of the formation of nonspecific and specific protective reactions;

A history of vaccination, etc.

Numerous environmental factors influence the state of the macroorganism and, consequently, the course of an infectious disease:

Temperature;

Humidity;

The level of radiation, etc.

Of particular importance is the influence of social factors on the development of an infectious disease in humans:

population migration;

The nature of the food;

stressful situations, etc.

The following aspects of the deteriorating environmental situation have an adverse effect on the macroorganism:

Radiation;

Gas contamination;

Carcinogenic substances, etc.

The deterioration of the external environment, most noticeable in recent decades, has an active influence on the variability of microorganisms, as well as on the formation of an unfavorable premorbid background in humans (in particular, immunodeficiency states). As a result, the typical clinical picture and the course of many infectious diseases change significantly.

In the practice of infectious disease doctors, the following concepts have taken root:

Classical and modern course of infectious disease;

Atypical, abortive, erased forms;

Exacerbations and relapses.

Atypical forms of an infectious disease are considered to be conditions that differ in the dominance in its clinical manifestations of signs that are not characteristic of this disease, or the absence of typical symptoms. For example, the predominance of meningeal symptoms (meningotif) or the absence of roseous exanthema in typhoid fever. Atypical forms also include an abortive course, characterized by the disappearance of the clinical manifestations of the disease without the development of its typical signs. With an erased course of the disease, the symptoms characteristic of it are absent, and the general clinical manifestations are mild and short-term.

An exacerbation of an infectious disease is considered a repeated deterioration in the general condition of the patient with an increase in the characteristic clinical signs of the disease after their weakening or disappearance. If the main pathognomonic signs of the disease develop again in the patient after the complete disappearance of the clinical manifestations of the disease, they speak of its relapse.

In addition to exacerbations and relapses, in any period of an infectious disease, it is possible development of complications. They are conditionally divided into specific (pathogenetically associated with the underlying disease) and nonspecific.

The causative agent of this infectious disease is the culprit of specific complications. They develop due to unusual severity of typical clinical and morphological manifestations of the disease (for example, acute hepatic encephalopathy in viral hepatitis, perforation of ileal ulcers in typhoid fever) or due to atypical localization of tissue damage (for example, endocarditis or arthritis in salmonellosis).

Complications caused by microorganisms of another species (for example, bacterial pneumonia with influenza) are considered nonspecific.

The most dangerous complications of infectious diseases:

Infectious-toxic shock (ITS);

Acute hepatic encephalopathy;

Acute renal failure (ARF);

swelling of the brain;

Pulmonary edema;

Hypovolemic, hemorrhagic and anaphylactic shock.

They are discussed in the corresponding chapters of the special part of the textbook.

Many infectious diseases are the possibility of developing microbial carriage. Carriage is a peculiar form of the infectious process, in which the macroorganism after the intervention of the pathogen is not able to completely eliminate it, and the microorganism is no longer able to maintain the activity of the infectious disease. The mechanisms of the development of carriage have not been sufficiently studied so far, methods for the effective rehabilitation of chronic carriers have not yet been developed in most cases. It is assumed that the formation of carriage is based on a change in immune responses, in which selective tolerance of immunocompetent cells to pathogen Ag and the inability of mononuclear phagocytes to complete phagocytosis are manifested.

Carrier formation can be facilitated by:

Congenital, genetically determined features of the macroorganism;

Weakening of protective reactions due to previous and concomitant diseases;

Reduced immunogenicity of the pathogen (decrease in its virulence, transformation into L-forms).

The following factors are associated with the formation of carriage:

Chronic inflammatory diseases of various organs and systems;

Helminthiases;

treatment defects;

The nature of the course of an infectious disease, etc. The duration of carriage of various pathogenic microorganisms can

vary extremely widely - from a few days (transient carriage) to months and years (chronic carriage). Sometimes (for example, with typhoid fever), the carrier state can persist for life.

PATHOGENETIC MECHANISMS OF INTOXICATION SYNDROME FORMED UNDER THE INFLUENCE OF THE LIPOPOLYSACCHARIDE COMPLEX

Thanks to numerous studies of domestic and foreign scientists, the mechanisms of successive responses that occur in the human body under the influence of bacterial endotoxins of most microorganisms have been deciphered. The combination of these reactions is the activation or inhibition of the functional state of various organs and systems of the body, which is expressed in the development of intoxication syndrome. From a biological point of view, intoxication syndrome is a systemic response of the body to the impact of a foreign agent.

The resistance of the human body to the penetration of endotoxin into the internal environment begins with the active destruction of the pathogen with the help of cellular (macrophages, polymorphonuclear leukocytes and other phagocytes) and humoral (specific and nonspecific) factors. First of all, there is recognition of LPS and other pathogen-associated molecules. (PAMP) through TLR. Without recognition and detection, a protective response of the macroorganism is impossible. In those cases when endotoxin manages to penetrate into the blood, the antiendotoxin defense system is activated (Fig. 2-1). It can be represented as a combination of non-specific and specific factors.

Rice. 2-1. Anti-endotoxin protection system

Nonspecific factors of antiendotoxin protection include cellular (leukocytes, macrophages) and humoral mechanisms. The participation of humoral factors in defense reactions continues to be studied, but the fact that high-density lipoproteins primarily stand in the way of endotoxin is no longer disputed. Possessing a unique ability to adsorb the LPS complex, they neutralize and then remove endotoxin from the human body.

The proteins of the acute phase of inflammation have the same properties:

Albumins;

Prealbumins;

Transferrin;

Haptoglobin.

Specific factors of antiendotoxin protection include Re-AT and glycoproteins (LBP) that bind the LPS complex to CD 14+ cells. Re-AT

are constantly present in the blood, as they are produced in response to the effects of endotoxin from the intestines. Consequently, the strength of the neutralizing antitoxin effect depends on their initial concentration, as well as on the ability of their rapid synthesis in cases of excessive intake of LPS complexes.

Glycoprotein (LBP) from the group of proteins of the acute phase of inflammation is synthesized by hepatocytes. Its main function is to mediate the interaction of the LPS complex with specific receptors of myeloid cells. CD 14+. LPS-complex and LBP enhance the reconciling effect of lipopolysaccharides on granulocytes, mediating the production of reactive oxygen species, TNF and other cytokines.

Only after overcoming the powerful mechanisms of antiendotoxin protection, the LPS complex begins to exercise its effect on the organs and systems of the macroorganism. At the cellular level, the main target of the LPS complex is the activation of the arachidonic cascade, which becomes the leading damaging factor in endogenous intoxication. It is known that the regulation of cell activity is also realized through the release of arachidonic acid from the phospholipids of the cell membrane. Under the action of catalysts, arachidonic acid is gradually cleaved to form PG (arachidonic cascade). The latter, through the adenylate cyclase system, regulate cell functions. Under the action of the LPS complex, the metabolism of arachidonic acid proceeds along the lipoxygenase and cyclooxygenase pathways (Fig. 2-2).

Rice. 2-2. Formation of biologically active substances from arachidonic acid

The end product of the lipoxygenase pathway is leukotrienes. Leukotriene B4 enhances chemotaxis and degranulation reactions, and leukotrienes C4, D4, E4 increase vascular permeability and reduce cardiac output.

When arachidonic acid is cleaved along the cyclooxygenase pathway, prostanoids (intermediate and final forms) are formed. Under the action of the LPS-complex, an excessive amount of thromboxane A 2 appears, causing vasoconstriction, as well as platelet aggregation throughout the vascular bed. As a result, blood clots form in small vessels and develop

microcirculatory disturbances leading to disruption of tissue trophism, retention of metabolic products in them and the development of acidosis. The degree of violation of the acid-base state (ACH) largely determines the strength of intoxication and the severity of the disease.

The development of microcirculatory disorders due to changes in the rheological properties of blood is the morphological basis of the intoxication syndrome. In response to the increased formation of thromboxane A 2 caused by the LPS complex, the vascular network begins to secrete prostacyclin and antiaggregation factors that restore the rheological properties of the blood.

The effect of the LPS complex on the cyclooxygenase pathway of arachidonic acid degradation is realized through the formation of a large amount of PGs (and their intermediate forms).

Their biological activity is manifested:

Vasodilation [one of the main factors in reducing blood pressure (BP) and even the development of collapse];

Contraction of smooth muscles (excitation of peristaltic waves of the small and large intestines);

Increased excretion of electrolytes, followed by water into the intestinal lumen.

The influx of electrolytes and fluid into the intestinal lumen, combined with increased peristalsis, is clinically manifested by the development of diarrhea leading to dehydration.

In this case, dehydration of the body goes through several successive stages:

Decreased volume of circulating blood plasma (blood thickening, increased hematocrit);

Decrease in the volume of extracellular fluid (clinically this is expressed by a decrease in skin turgor);

The development of cellular overhydration (acute edema and swelling of the brain).

In addition, PG exhibit pyrogenic properties, their excessive formation leads to an increase in body temperature.

Simultaneously and in interaction with the arachidonic cascade, the LPS complex activates myeloid cells, which leads to the formation of a wide range of endogenous lipid and protein mediators (primarily cytokines), which have exceptionally high pharmacological activity.

Among cytokines, TNF occupies a leading place in the realization of the biological effects of the LPS complex. This is one of the first cytokines, the level of which increases in response to the action of the LPS complex. It contributes to the activation of the cytokine cascade (primarily IL-1, IL-6, etc.).

Thus, the initial damaging phase of the intoxication syndrome, which is formed under the influence of the LPS complex, is realized through the activation of the arachidonic and cytokine cascades, resulting in a breakdown in the control system of cellular functions. In such situations, ensuring the vital activity of the human body and maintaining its homeostasis require the inclusion of higher regulatory mechanisms. The tasks of the latter include creating conditions for removing the pathogen source of LPS-complexes and restoring unbalanced functions.

cell systems. This role is performed by biologically active compounds involved in adaptive mechanisms, as well as regulating systemic reactions of the body.

For the first time, the role of glucocorticoid hormones in the development of stress syndrome as an adequate adaptive response to damage was determined by the Canadian biochemist Hans Selye. At the height of intoxication, the adrenal cortex is activated, leading to an increased release of glucocorticoids into the blood. These reactions control blood pressure in conditions of increased vascular permeability and a sharp change in the rheological properties of blood (increased thrombus formation, microcirculation and trophic disorders of organs). With the depletion of the potential and reserve capabilities of the adrenal cortex, acute cardiovascular insufficiency (collapse) develops.

The regulatory role of the renin-angiotensin-aldosterone system increases at the height of endogenous intoxication, especially against the background of dehydration of the body (diarrhea in acute intestinal infections). Due to its activation, the body tries to maintain the water-electrolyte composition in liquid volumes, i.e. maintain the constancy of homeostasis.

Activation of plasma kallikreinogenesis under conditions of intoxication leads to a change in the phase structures of the systoles of the left and right ventricles of the heart.

At the height of intoxication, the exchange of serotonin and histamine increases, which is directly related to platelet aggregation in the vascular bed and the state of microcirculation.

There is an intensive study of the participation of the catecholamine system in the development of intoxication, as well as other systems involved in the management of vital body functions.

Analyzing the given data on the known and studied mechanisms for the development of the intoxication syndrome, special attention should be paid to 2 provisions:

The sequence of inclusion of protection mechanisms;

Interaction of various control systems of functions of organs and systems of the body.

Exactly interaction of management systems aimed at preserving and(or) restoration of homeostasis of the human body, can be defined as an adaptation syndrome.

Activation of regulatory mechanisms arising in response to the damaging effect of the LPS complex is realized through the functionality of various organs and systems. With the development of intoxication, almost all organ cell systems are involved in the process of maintaining the homeostasis of the body and removing endotoxin. On fig. 2-3 shows the systemic reactions of the body against the background of intoxication.

On the basis of general pathological approaches, a concept of the medical and biological significance of the intoxication syndrome in the development of infectious diseases was developed. The intoxication syndrome is of unique importance for the clinic of infectious diseases, since, on the one hand, it represents a universal clinical syndrome complex, the development of which is typical for most infectious diseases, regardless of the etiological factor, and, on the other hand, the degree of its severity determines the severity and outcome of the disease. In general pathological terms, the intoxication syndrome is clinical

Rice. 2-3. Systemic reactions of the body in response to intoxication

equivalent to the urgent adaptation of the organism in conditions of microbial invasion. Of exceptional importance for the clinic of infectious diseases is the establishment of the nature of the failure in the regulation of the adaptive potential of the body, which is clinically manifested by more severe forms of the disease, the development of complications and, in extreme cases, death.

It must be emphasized that changes in the parameters of the functional state of a single organ or a single cellular system in case of intoxication syndrome often do not always indicate damage to this organ or system. On the contrary, deviations of indicators of the functional state of an organ from normal may be an indicator of the need to compensate for damaged functions or their temporary replacement (for example, tachycardia during dehydration).

Organ pathology should be discussed only if the infectious agent directly affects the tissue of the organ (for example, with HAV)

or there is a depletion of the reserve capacity of the body during its hard work. Pathological changes and reactions of organ systems (positive or negative) are presented in the "Special Part" section.

Extremely unfavorable outcome of infectious diseases - ITSH development, and with some of them (for example, in the terminal stage of cholera, salmonellosis) and hypovolemic shock(Fig. 2-4).

The clinical picture of shock is described in the relevant sections of this textbook. However, it is necessary to imagine what mechanisms underlie this condition, which is a shock from a pathophysiological perspective.

According to the authors of the textbook, a shock can occur against the background of the spent reserves of the body, without the restoration of which conditions are created that are incompatible with life. However, this state can be reversible if the missing reserves are replenished from the outside.

At the same time, it is known that in the body of a person who died from shock, in a number of cases, vital reserves remain far from being fully used. In this situation, the shock, apparently, occurs due to the failure of the control system for the functions of organs and systems. At the current level of development of biology and medicine, it is extremely difficult to restore this pathogenetic mechanism due to still insufficient knowledge in this area and, consequently, the inability to develop a system to combat this condition. In these cases, the shock should be considered irreversible.

PATHOGENESIS OF VIRAL DISEASES

The main difference between viruses and other infectious agents is the mechanism of their reproduction. Viruses are not capable of self-replication. The pathogenesis of viral infections is based on the interaction of the virus genome with the genetic apparatus of the sensitive cell. Some viruses can replicate in a wide variety of cells, while others replicate only in cells of certain tissues. This is due to the fact that the number of specific receptors that ensure the interaction of the virus with cells is limited in the latter case. The entire replication cycle of the virus is carried out using the metabolic and genetic resources of the cell. Therefore, the nature of the development of interstitial processes is determined, on the one hand, by the cytopathic effect of the virus on the cells of a given tissue and organ, and on the other hand, by the reaction of interstitial and organ defense systems against the virus. The latter are often destructive in nature, aggravating the course of the disease.

The spread of viruses in the body can be local or systemic.

With the exception of lesions caused by viruses that spread through the nervous tissue, viral infection occurs with viremia. Viremia is characterized by the degree of viral load, directly correlated with the degree of general toxicosis, the severity of the patient's condition.

Viremia leads to excessive secretion of lymphokines by endothelial cells and damage to the walls of blood vessels with the development of hemorrhages, capillary toxicosis, tissue hemorrhagic edema of the lungs, kidneys and other parenchymal organs. A number of viruses are characterized by the induction of programmed cell death, i.e. apoptosis of infected cells.

Rice.2 -4. Scheme of the development of intoxication (Malov V.A., Pak S.G., 1992)

Many viruses infect immunocompetent cells. This is more often manifested by dysfunction and a decrease in the number of T-helpers, which leads to hyperactivation of the B-cell link of immunity, but with a decrease in the functionality of plasma cells in the synthesis of high-affinity antibodies. At the same time, there is an increase in the content and activation of T-suppressors, as well as B-cells.

There are latent forms of viral infections, in which viruses remain in the body for a long time without clinical manifestations, but under the influence of adverse factors they can reactivate and cause an exacerbation of the disease (most herpes viruses), as well as the development of slow infections. The latter are characterized by a long incubation period (months and years), during which the pathogen multiplies, causing obvious tissue damage. The disease ends with the development of severe lesions and death of the patient (subacute sclerosing panencephalitis, HIV infection, etc.).

MAIN CLINICAL MANIFESTATIONS

INFECTIOUS DISEASES

The division of diseases into infectious and non-infectious is very conditional. In the vast majority of cases, the disease is the result of the interaction of an infectious agent (bacteria, viruses, etc.) and a macroorganism. At the same time, many types of inflammatory lesions of the lungs (pneumonia), heart (septic endocarditis), kidneys (nephritis, pyelonephritis), liver (abscesses) and other organs are not formally classified as infectious diseases.

If the epidemiological factor is taken as the basis for the division of these groups of diseases, then diseases such as tetanus, brucellosis, botulism and many others classified as infectious do not pose an epidemic danger in the team. At the same time, chronic viral hepatitis, which is mainly treated by therapists, can be transmitted from person to person.

Taking into account the above circumstances, this section provides a clinical description of the main symptoms and syndromes that occur during the interaction of micro- and macro-organisms in the development of diseases, regardless of whether they are classified as infectious or non-infectious.

The vast majority of infectious diseases are characterized by general toxic syndrome. Clinically, it is a frequent combination of fever with numerous other manifestations of intoxication.

Fever- any increase in body temperature over 37 °C. Its character (temperature curve) is very typical for many infectious diseases, which is an important diagnostic sign. It is not characteristic of only a few manifest forms of infectious diseases (for example, cholera and botulism). Fever may also be absent in mild, obliterated or abortive disease.

The main criteria for fever:

duration;

Height of body temperature;

The nature of the temperature curve.

Most often, acute fever is observed lasting no more than 15 days. Fever lasting from 15 days to 6 weeks is called subacute, more than 6 weeks - subchronic and chronic. By height, body temperature is divided into subfebrile (37-38 ° C), moderate (up to 39 ° C), high (up to 40 ° C) and hyperpyretic (over 41 ° C).

According to the nature of the temperature curve, taking into account the difference between the highest and lowest temperature per day, the following main types of fever are distinguished.

. Constant fever (febris continua). Fluctuations between morning and evening temperatures are typical, not exceeding 1 °C. It is observed in typhoid and typhus, yersiniosis, lobar pneumonia.

. Laxative or remittent fever (febris remittens). Daily temperature fluctuations are typical (not falling to the norm) ranging from 1-1.5 °C. They are observed in some rickettsiosis, tuberculosis, purulent diseases, etc.

. Intermittent, or intermittent, fever (febris intermittens). Regular alternations of periods of increase in body temperature are characteristic, as a rule, fast and short-term (paroxysms of fever), with fever-free periods (apyrexia). At the same time, its minimum indicators for 1 day lie within the normal range. This type of fever is noted in malaria, some septic conditions, visceral leishmaniasis.

. Relapsing fever (febris reccurens). Presented by alternating bouts of high body temperature with its rapid rise, critical fall and periods of apyrexia. The feverish attack and apyrexia last for several days. This type of fever is characteristic of relapsing fever.

. Hectic or exhausting fever (febris hectica). Characterized by sharp increases in body temperature by 2-4 ° C and its rapid fall to a normal level and below, which are repeated 2-3 times during the day and are accompanied by profuse sweating. Occurs in sepsis.

. Undulating or undulating fever (febris undulans). Characterized by a temperature curve with a change in periods of gradual increase in temperature to high numbers and its gradual decrease to subfebrile or normal values. These periods last several days (brucellosis, some forms of yersiniosis, recurrent typhoid fever).

. Irregular, or atypical, fever (febris irregularis, sine atypica). Various and irregular daily fluctuations of indefinite duration are characteristic. They are observed in many infectious diseases (flu, diphtheria, tetanus, meningitis, anthrax, etc.).

. Reverse fever. Sometimes they meet with brucellosis, septic conditions. In this case, the morning body temperature exceeds the evening.

During the fever, three periods are distinguished:

rises;

stabilization;

Decrease in body temperature.

The allocation of these periods with their clinical assessment is important for diagnosing an infectious disease and for determining a set of measures for medical care for a patient.

With an acute onset of the disease (flu, typhus, meningococcal meningitis, erysipelas, leptospirosis, etc.), the increase in body temperature to high numbers occurs quickly, within 1 day or even several hours. The gradual onset of the disease is accompanied by an increase in fever over several days, as happens, for example, in cases of the classic course of typhoid fever. The fever ends either very quickly, after a few hours (critical decrease in temperature), or slowly, gradually, over several days (lytic decrease).

In some cases, with a severe course of an infectious disease, hypothermia is noted - not an increase, but a drop in body temperature below normal levels. The combination of hypothermia with increasing symptoms of intoxication and hemodynamic disorders is extremely unfavorable and indicates the development of TSS.

Fever in infectious diseases is usually accompanied by other manifestations of intoxication associated with lesions of various organs and systems. With the development of toxemia, first of all, signs of CNS damage are observed (headache, weakness, malaise, sleep disturbance), or more pronounced signs of toxic encephalopathy (excitation or apathy, emotional lability, anxiety, impaired consciousness of varying degrees up to deep coma).

Intoxication also leads to disorders of cardiovascular activity:

Bradycardia or tachycardia;

Deafness of heart sounds;

Decrease or increase in blood pressure.

There are changes in the color of the skin and mucous membranes (icterus, cyanosis, pallor or hyperemia), dryness of the mucous membranes and thirst, a decrease in the amount of urine excreted (oliguria, anuria) and many other clinical symptoms.

Important diagnostic features revealed during examination of an infectious patient are changes in the skin and mucous membranes- their coloring, elasticity and humidity, various rashes on them. Paleness of the skin may indicate spasm of blood vessels or deposition of blood in the abdominal cavity (for example, with TSS). The appearance of cyanosis is associated with severe metabolic disorders and tissue hypoxia (with meningococcemia, severe salmonellosis, sepsis, etc.).

Some infectious diseases (influenza, typhus, pseudotuberculosis) are characterized by hyperemia of the skin, mainly of the face and upper body. Due to liver damage or hemolysis of red blood cells, icteric staining of the skin, sclera and mucous membranes (viral hepatitis, leptospirosis) can be observed.

Dryness of the skin and a decrease in its elasticity (turgor) indicate significant dehydration. Severe sweating is observed in malaria, brucellosis, sepsis, pneumonia. It usually accompanies the stages of a critical decrease in body temperature.

Many infectious diseases are characterized skin rashes (exanthema).

The elements of the rash are quite diverse:

roseola;

spots;

Erythema;

hemorrhages;

papules;

Vesicles;

Pustules;

blisters.

Later, the primary elements of the rash may be replaced by the formation of scales, age spots, ulcers and scars. Of great diagnostic importance are the nature of the exanthema, the timing of its appearance (day of illness), the sequence (stages) of rashes, the predominant localization, the number of elements of the rash and the subsequent dynamics of their development.

In some transmissible infections (tularemia, borreliosis, etc.), at the site of the introduction of the pathogen into the skin, primary affect- a site of inflammation of the skin, preceding other clinical manifestations of the disease.

Examination of the mucous membranes reveals enanthem with the formation of vesicles, erosions and ulcers, small hemorrhages (Chiari-Avtsyn spots on the transitional fold of the conjunctiva in patients with typhus), foci of epithelial necrosis (Belsky-Filatov-Koplik spots on the mucous membrane of the cheeks with measles).

Of great diagnostic importance is the revealed changes in the mucous membranes of the eyes:

Hyperemia of the conjunctiva;

Injections of vessels of the sclera (influenza, measles, leptospirosis);

The formation of fibrinous films on the conjunctiva with a sharp swelling of the eyelids (diphtheria of the eye, membranous adenoviral conjunctivitis).

You can observe changes in the color of the mucous membranes - icterus of the sclera, soft palate, frenulum of the tongue with liver damage, cyanotic tint of the mucous membranes of the oropharynx with diphtheria.

Many infectious diseases accompany lymphadenopathy- swollen lymph nodes. During examination and palpation, their size, consistency, soreness, mobility, their cohesion with the surrounding tissue and skin (periadenitis) are assessed. In unclear diagnostic cases, a puncture and a biopsy of the lymph nodes are performed. Specific changes in isolated groups of lymph nodes, the so-called regional lymphadenitis, are observed in plague, tularemia, felinosis (cat scratch disease), diphtheria, and various kinds of tonsillitis. Such changes are called regional because they develop near the entrance gate of infection and represent the place of primary localization and accumulation of the pathogen. When 2-3 groups of lymph nodes or more are involved in the process, they speak of generalized lymphadenopathy. It is characteristic of HIV infection, brucellosis, infectious mononucleosis, chlamydia, etc.

Some infections are joint damage in the form of mono-, poly- and periarthritis (brucellosis, yersiniosis, meningococcal infection, borreliosis).

catarrhal respiratory syndrome is pronounced in ARVI and manifests itself:

runny nose;

cough;

sneeze;

Pain and irritation in the throat and nasopharynx.

When examining patients, hyperemia is revealed, in some cases swelling of the mucous membranes of the upper respiratory tract, raids of a diverse nature (loose follicular or lacunar with angina of coccal etiology, fibrinous localized or common with diphtheria, etc.). Often develop bronchitis, bronchiolitis and pneumonia; the latter in some infectious diseases are specific (Q fever, legionellosis, mycoplasmosis, ornithosis).

Changes in the cardiovascular system characteristic of many infectious diseases and are often associated with the development of intoxication. However, in some infections, changes in the heart and blood vessels are specific manifestations of the disease (diphtheria, hemorrhagic fevers, typhus, meningococcal infection).

For the clinical picture of acute intestinal infections, the most typical diarrhea. It is usually combined with a variety of dyspeptic disorders that differ significantly in different intestinal infections - abdominal pain, nausea and vomiting, appetite disorders, as well as fever and other symptoms of general intoxication (shigellosis, salmonellosis, escherichiosis, yersiniosis, viral enteritis, etc.) . Since the nature of the stool is associated with the development of pathological processes in different parts of the gastrointestinal tract, an examination plays an important role in the diagnosis of intestinal infections. When the small intestine is affected, enteric stools are observed - frequent and plentiful, liquid, watery, with particles of undigested food, frothy, fetid, greenish or light yellow in color. In the pathological process in the colon, colitis is observed - mushy or semi-liquid consistency, brown, frequent, the volume of feces tends to decrease with each subsequent bowel movement. Pathological impurities in the form of mucus or blood can be detected in the feces. With severe colitis, stools are scanty and consist only of mucus, streaks or droplets of blood, sometimes impurities of pus (rectal spitting). In this case, one can observe false urges and painful contractions of the large intestine - tenesmus.

Typhoid-paratyphoid diseases can complicate the development of heavy intestinal bleeding. In this case, the stool takes on a tarry appearance. (melena).

At the same time, it should be borne in mind that the nature of the stool (primarily its color) may be associated with the food products used by the patient (beets, blueberries, etc.).

One of the important manifestations of many infectious diseases, accompanied by the circulation of the pathogen in the blood, is hepatolienal syndrome. It is expressed in a combined increase in the liver and spleen, which is explained by active reactions of the reticulohistiocytic tissue in these organs.

Hepatolienal syndrome is formed with viral hepatitis, brucellosis, leptospirosis, malaria, typhus, typhoid paratyphoid and others.

infectious diseases occurring in a generalized form. With the help of percussion and palpation, the size of the liver and spleen, their consistency, sensitivity or soreness of the organs are assessed.

meningeal syndrome develops with meningitis of various etiologies. It is usually associated with general toxic manifestations and changes in the cerebrospinal fluid. The ability to identify its signs is extremely important for the early diagnosis of diseases and the timely start of full-fledged treatment, on which the fate of the patient often depends. Meningeal syndrome includes cerebral and meningeal symptoms.

Cerebral symptoms - a headache of a diffuse, bursting nature, growing in strength, sudden vomiting without previous nausea and, as a rule, not bringing relief to the patient, as well as impaired consciousness of varying degrees, up to deep coma.

Shell symptoms - auditory, visual and tactile hyperesthesia, pain when pressing on the eyeballs with closed eyelids, at the points of exit of the branches of the trigeminal nerve and occipital nerves, with percussion of the skull.

Along with cerebral and meningeal symptoms, meningeal symptoms occur in the form of stiff neck muscles, symptoms of Kernig, Brudzinsky, etc.

Rigidity of the neck muscles is detected when trying to passively bend the head of the patient, lying on his back, to his chest.

Kernig's symptom is expressed in the impossibility of complete passive extension in the knee of the patient's leg previously bent at a right angle in the hip joint (checked on both sides).

The upper symptom of Brudzinsky is determined in a patient lying on his back, simultaneously with an attempt to detect stiff neck: in this case, one or both legs of the patient spontaneously bend at the knee and hip joints. The same spontaneous bending of the patient's legs in his supine position can occur when pressing on the pubic joint or when checking the Kernig symptom (middle and lower Brudzinsky symptoms, respectively).

Along with the above main meningeal symptoms, the presence of many others is possible (Guillain, Gordon, suspension symptom, or Lessage, etc.).

For children of the first year of life, bulging and tension of a large fontanel are characteristic. At an older age, a symptom of landing (tripod) appears: when trying to sit up in bed, the child takes his hands back and leans them on the bed, supporting the body in an upright position.

The severity of individual signs and meningeal syndrome as a whole may be different, however, in all cases, a lumbar puncture and examination of the cerebrospinal fluid (CSF) are indicated.

In the absence of changes in the cerebrospinal fluid in a patient with positive meningeal symptoms, they speak of meningism. The condition can develop in infectious diseases accompanied by severe general toxic reactions, such as influenza.

Along with the listed main syndromes, in some infectious diseases, specific lesions of individual organs are detected:

Kidney - with hemorrhagic fever with renal syndrome (HFRS) and leptospirosis;

Genital organs - with brucellosis, mumps, etc.

BASIC METHODS FOR DIAGNOSTICS OF INFECTIOUS DISEASES

Diagnosis of infectious diseases is based on the integrated use of clinical, laboratory and instrumental methods of examination.

Clinical diagnostics

Clinical methods include:

Identification of patient complaints;

Anamnesis information (medical history, epidemiological history, basic information from the life history);

Clinical examination of the patient.

History of infectious disease find out by actively questioning the patient: a detailed identification of his complaints at the time of examination by a doctor, the time and nature of the onset of the disease (acute or gradual), a detailed and consistent description of the occurrence of individual symptoms and their development in the dynamics of the disease. In this case, one should not be limited to the patient's story (if his condition allows), the anamnestic data is clarified as detailed as possible. This gives the clinician the opportunity to form a preliminary impression of a likely clinical diagnosis. An old rule of clinicians says: "The history is half the diagnosis."

When collecting anamnestic information from infectious patients, special attention should be paid to the data epidemiological history. In this case, the doctor aims to obtain information about the place, circumstances and conditions under which infection could occur, as well as about the possible ways and methods of transmission of the infectious agent to this patient. Find out the contacts and frequency of communication of the patient with other sick people or animals, his stay in places where infection could occur (in endemic or epizootic foci). Pay attention to the possibility of insect and animal bites, any damage to the skin (injuries, injuries), therapeutic parenteral interventions.

When clarifying life history pay attention to the conditions of life, food, work and rest of the patient. Information about previous diseases, including infectious ones, and the treatment carried out during this, is extremely important. It is necessary to find out whether the patient has been vaccinated (what and when), whether there is a history of indications for the administration of sera, immunoglobulins, blood products and blood substitutes, as well as possible reactions to them.

Clinical examination the patient is carried out in a certain order in accordance with the scheme of the case history. A consistent and detailed examination allows you to identify the symptoms and syndromes characteristic of an infectious disease (see the section "The main clinical manifestations of infectious diseases").

First of all, assess the general condition of the patient:

Preservation of consciousness or the degree of its violation;

Excitation or lethargy;

Mental disorders;

Appropriate behavior.

In accordance with the established procedure, an examination is carried out:

Skin and mucous membranes;

Peripheral lymph nodes;

Assess the state of the musculoskeletal system, respiratory, cardiovascular systems, gastrointestinal tract, urinary organs, genitals, nervous system.

Based on the information obtained by the doctor when identifying the anamnestic information, and the data of the clinical examination of the patient, a preliminary diagnosis is formulated.

In accordance with the diagnosis (with an assessment of the form and severity of the disease, the period of illness, complications and concomitant diseases), the doctor determines:

The place of hospitalization of the patient in the infectious diseases hospital, department (if necessary, intensive care unit), ward or isolated box;

Develops a plan for laboratory and instrumental examination, consultations of specialists;

Makes up a treatment plan for the patient (regimen, diet, drug treatment).

All these data are entered into the medical history.

Laboratory and instrumental diagnostics

Methods of laboratory and instrumental diagnostics are divided into general (for example, general blood and urine tests, chest x-ray) and specific (special) methods used to confirm the alleged diagnosis of an infectious disease and assess the severity of the disease. The data of specific studies are also necessary to control the recovery, determine the terms and conditions for the discharge of the patient.

Depending on the nosological form of the disease, its nature and period, a specific study may be subject to:

Blood;

Feces;

Urine;

Sputum;

cerebrospinal fluid;

duodenal contents;

Washings from mucous membranes;

Punctates and biopsies of organs;

discharge of ulcers;

sectional material. Laboratory research methods

Bacteriological studies provide for sowing on nutrient media of various material taken from the patient (blood, urine, cerebrospinal fluid, feces, etc.), isolating a pure culture of the pathogen, as well as determining its properties, in particular type and sensitivity to antibiotics. During outbreaks of intestinal infections, bacteriological examination is carried out on food residues, which may be associated with infection of those who used it. Bacteriological examination takes at least a few days.

Virological research include the isolation and identification of viruses. When they are carried out, tissue cultures, chicken embryos, laboratory animals are used. Quite often, such studies are carried out in secure laboratories.

Immunological methods are based on the detection of pathogen Ag or antibodies to them.

Ag of the pathogen is detected in feces, blood serum, cerebrospinal fluid, saliva and other biological material obtained from the patient. For this apply:

Coagglutination reactions (RCA);

Latex agglutination reactions (RLA);

RNGA;

IFA etc.

The reactions are based on the use of special diagnostic preparations (diagnosticums), which are a carrier (lyophilized staphylococcus, latex particles, erythrocytes) with a highly active serum fixed on it against one or another pathogen Ag. The reactions are highly specific and can be used as express diagnostic methods in the early stages of the disease.

Abs in whole blood serum or its fractions containing immunoglobulins of various classes can be detected using many specific laboratory methods.

The most popular of them:

RA - with brucellosis, yersiniosis, tularemia, some rickettsiosis and other infections;

RNGA - with many intestinal infections;

RTGA - with various viral infections.

In rickettsiosis and some viral diseases, the complement fixation reaction (RCC), radioimmunoassay (RIA) and ELISA are of great diagnostic value. Research is carried out with known Ag. Determining the affiliation of antibodies to different classes of immunoglobulins helps to clarify the phase of the infectious process, to distinguish a primary infectious disease from a recurrent one (for example, typhus from Brill-Zinsser disease), to differentiate an infectious disease from post-vaccination reactions.

At the same time, methods for detecting antibodies also have significant drawbacks. As a rule, positive results of reactions can be obtained no earlier than the 2nd week of the disease, when serum titers of antibodies begin to exceed the minimum diagnostic level. Weak or delayed formation of antibodies is observed in individuals with a reduced activity of the immune system, as well as in many infectious diseases, the causative agents of which exhibit high immunosuppressive activity (yersiniosis, abdominal

typhus, etc.). The diagnostic value of reactions increases in the study of paired sera taken with an interval of 7-10 days. In these cases, the dynamics of the increase in titers of antibodies is traced, which is most important in viral infections, when only an increase in titers in the 2nd serving of serum by 4 times or more is of diagnostic value.

In recent years, other immunological methods have been widely used in healthcare practice - the determination of markers of viral hepatitis (Ag of viruses and antibodies to them), the determination of immunoglobulins of various classes, the quantitative content of T-lymphocytes, immunoblotting, etc.

Currently, polymerase chain reaction (PCR) is of great importance for the diagnosis of infectious diseases, which reveals the minimum amount of nucleic acids of almost any pathogenic agent in various biological fluids and cellular elements of the macroorganism.

Skin allergy tests used for allergic diagnosis of brucellosis, tularemia, anthrax, toxoplasmosis, psittacosis and other infectious diseases. To do this, 0.1 ml of a specific allergen (protein extract of the pathogen culture) is injected intradermally or applied to scarified skin. The test is considered positive if hyperemia, edema and infiltrate appear at the site of allergen injection after 24-48 hours, the severity of which is used to judge the intensity of the reaction.

A significant place in the practice of an infectious disease specialist is occupied by biochemical research methods. They are especially popular for infectious diseases accompanied by lesions of the liver, kidneys, cardiovascular, endocrine systems, etc.

Instrumental research methods

For the differential diagnosis of some intestinal infections and to establish the nature and depth of damage to the mucous membrane of the rectum and sigmoid colon, sigmoidoscopy has long been practiced. The method allows you to examine the condition of the mucous membrane of the large intestine throughout, but not further than 30 cm from the anus. Recently, sigmoidoscopy is inferior in diagnostic value to fibrocolonoscopy and x-ray examination (irrigoscopy), which reveals pathological changes at the level of deeper sections of the intestine.

With echinococcosis and alveococcosis, the localization and intensity of lesions can be detected using a liver scan. When detecting focal lesions of visceral organs, the most popular methods of ultrasound examination (ultrasound). They are invaluable in the differential diagnosis of diseases accompanied by jaundice (viral hepatitis, neoplasms of the liver and its gate area, stones in the bile ducts and gallbladder, etc.). For this purpose, laparoscopy and puncture liver biopsy are also used.

In the diagnosis of infectious diseases, X-ray methods of research are also used (especially the study of the lungs in ARVI), electrocardiography (ECG) and computed tomography (CT).

The presented research methods are most often used in infectious practice, however, for the diagnosis of infectious diseases and especially differential diagnosis, it is necessary to use any other methods used by clinicians.

GENERAL PRINCIPLES FOR THE TREATMENT OF INFECTIOUS PATIENTS

Advances in the field of early diagnosis and treatment of infectious diseases, great achievements in epidemiology and the improvement of the social and living conditions of people now make it possible to observe and treat patients with some infectious diseases who were previously hospitalized on an outpatient basis (in a polyclinic and at home). These diseases include PTI, shigellosis, HAV and a number of others. Of course, it is desirable (with the consent of patients) their hospitalization with the listed diseases according to clinical indications - in cases of severe and protracted course, complications, severe concomitant diseases.

At the same time, the general principles for the treatment of infectious patients in outpatient and inpatient settings remain the same.

Mode of infectious patients

The mode of infectious patients is determined by the attending physician in accordance with the following conditions: the severity of the disease, the timing of the infectious process, the severity of the pathology of certain organs and systems, as well as the possibility of developing complications. The regimen prescribed to the patient is noted in the medical history.

Mode I - strictly bed. The patient is forbidden to sit down and even more so to get up; care for him, feeding and all medical manipulations are carried out with the patient in bed. In some infectious diseases (typhoid and typhus, etc.), strict bed rest is prescribed for a long time. It is necessary to explain to the patient the reasons for the appointment of bed rest, the possible consequences of its violation and strictly monitor its observance.

Mode II - semi-bed (ward). It is possible for the patient to independently visit the toilet, treatment room, meals in the ward, but it is recommended to spend most of the time in bed.

Mode III - general. Assign with good health and satisfactory condition of the patient, if the risk of complications and consequences of the disease is completely excluded. The patient is allowed to independently serve himself, visit the dining room.

The mode of the infectious diseases department also applies to medical personnel, who should try to eliminate as much as possible the factors that disturb the patient's peace:

Unrestrained and harsh tone in dealing with him;

Loud conversations in the wards and corridors.

Silence is especially important at night. The severity of the patient's condition should not be discussed in his presence, even if the patient is unconscious.

Infectious disease care

Qualified care for infectious patients contributes to their recovery, prevention of complications, and helps to prevent infection of others.

It is very important to maintain an even, calm tone in communication with patients. It should be remembered that the patient's irritability and rudeness can be caused not only by a low level of culture and moral principles, but also by a peculiar reaction to the environment, shifts in the psycho-emotional state due to a long and severe infectious disease. At the same time, the necessary measures should be persistently carried out and the patient should be forced to comply with the regimen of the infectious diseases department. This requires a medical worker to know the basic principles of medical ethics and deontology, including the features of subordination, professional behavior, appearance, and the ability to apply them in everyday activities.

In the infectious disease department, it is necessary to systematically carry out wet cleaning of the premises with the use of disinfectants, ventilation of the wards. Particular attention is paid to the cleanliness of the body and bed of the patient. Patients are washed in a bath or shower at least once a week. If this is contraindicated, daily wipe the patient's skin with a towel moistened with warm water. Seriously ill patients are treated with oral and nasal cavity, prevention of bedsores and congestive pneumonia, and control of physiological functions.

Nutrition of the sick

Nutrition of patients is carried out taking into account the specifics of the development of an infectious disease. Nutrition should be high in calories and meet all the body's needs for food, fluids, vitamins and salts. Infectious patients and convalescents are fed at least 4 times a day (breakfast, lunch, afternoon tea and dinner) at a strictly defined time. Seriously ill people are given small portions of food 6-8 times a day.

Dietary nutrition is prescribed by the attending physician, the observance of the diet by the patient is controlled by the nurse. Products brought by visitors are checked in their presence and immediately returned if they do not comply with the prescribed diet. It is necessary to systematically control the conditions of storage of products brought to the patient in bedside tables and specially designated refrigerators.

In general, the nutrition of infectious patients is carried out using certain types of diets that correspond to the identified pathology.

Most often, the following types of diets are used in infectious hospitals.

Diet number 2 is prescribed for acute intestinal infections during the convalescence period for a long time. It provides for mechanical and thermal sparing of the gastrointestinal tract. The table is mixed, all dishes are prepared in pureed and chopped form. Exclude beans, beans, green peas.

Diet number 4 is recommended for diarrhea, accompanied by significant irritation of the gastrointestinal mucosa (dysentery, salmonellosis, some forms of escherichiosis, etc.). They allow meat broths, slimy soups, boiled meat in the form of cutlets and meatballs, boiled fish, pureed cereals, jelly, jelly, fruit juices enriched with vitamins. Exclude products that cause fermentation processes and increased intestinal motility: cabbage, beets, pickles and smoked meats, spices, milk, natural coffee.

A slightly modified diet No. 4 (in infectious diseases hospitals it is sometimes referred to as diet No. 4abt) prescribed for typhoid fever and paratyphoid during the entire febrile period and 10-12 days of apyrexia. The diet provides maximum mechanical and chemical sparing of the intestines, a decrease in peristalsis and fermentation processes. They allow low-fat beef or chicken broths, slimy cereal soups, pureed cereals on the water, meat in the form of meatballs, soufflé or steam cutlets, boiled fish, soft-boiled eggs, white bread crackers. From the 10-12th day of apyrexia, the diet is supplemented with the inclusion of white half-baked bread (up to 150-200 g / day). Food should be fortified with vitamins. Kissels, berry and fruit juices, pureed apples are recommended. The amount of liquid is 1.5-2 l / day (tea, cranberry juice, rosehip broth). Limit fats, carbohydrates, coarse fiber.

Diet No. 5a is indicated in the acute stage of viral hepatitis and in exacerbation of chronic hepatitis. To minimize the load on the liver, animal fats and extractives are limited, and fried foods are excluded. Dishes are prepared mostly in pureed form. They allow yesterday's baking bread, vegetable, cereal and pasta soups on vegetable or non-concentrated meat and fish broths, milk and fruit soups; lean meat, fish and poultry in boiled form; pureed cereals (especially buckwheat) on water or with the addition of milk; eggs, milk, butter and vegetable oil (as additives to dishes); fresh dairy products and cottage cheese (soufflé); fruits, berries, jam, honey, kissels, jelly, compotes, weak tea. Exclude snacks, mushrooms, spinach, sorrel, turnip, radish, lemon, spices, cocoa, chocolate.

Diet No. 5 is prescribed during the recovery period for acute viral hepatitis or during remission for chronic hepatitis. In addition to the products of diet No. 5a, soaked herring, non-acidic sauerkraut, vegetables and greens are allowed in raw form or in the form of salads, vinaigrettes; milk, cheese, omelets. Food is not crushed.

Diet number 15 (general table) is prescribed in the absence of indications for a special diet. Physiologically complete diet with a high content of vitamins.

In the unconscious state of patients or with paralysis of the swallowing muscles (for example, with botulism, diphtheria), feeding is carried out through a nasal probe inserted by a doctor. Use 100-200 ml of a heated nutritional mixture of milk, kefir, broths, eggs, fruit juices, butter, etc. Liquids and medicines are also injected through the probe.

The calories necessary for a seriously ill patient are partially replenished by parenteral nutrition, in which the following is administered intravenously:

Hydrolysates;

Amino acids;

salt;

vitamins;

5% glucose solution ♠ ;

Special nutritional mixtures.

In febrile conditions and dehydration, infectious patients often need to drink plenty of water (up to 2-3 l / day). Recommend mineral water, tea with lemon, fruit drinks (cranberry, blackcurrant, etc.), a variety of fruit and berry juices. With dehydration and demineralization, oral and intravenous administration of polyionic crystalloid isotonic solutions is prescribed.

Medical treatment

Comprehensive medical treatment of infectious patients involves taking into account the etiology and pathogenesis of the disease, a thorough analysis of the individual condition of the patient, his age and immunological characteristics, the period and severity of the infectious disease, complications and concomitant diseases.

One of the most important areas of complex treatment of infectious patients is etiotropic treatment, those. effect on the pathogen. During its implementation, antibiotics and chemotherapy drugs are used.

When choosing a drug, it is important to follow certain rules.

The causative agent must be sensitive to the agent used.

The concentration of the chemotherapy drug (antibiotic) in the focus of infection should be sufficient to suppress the vital activity of the pathogen (bactericidal or bacteriostatic effect).

The drug should be administered in such a way and at such an interval that the required concentration is maintained in the focus of infection.

The negative effect of the drug on the macroorganism should be less than its healing effect.

The drug should be administered for as long as required to completely suppress the vital activity of the pathogen.

It is impossible in the course of treatment to lower the dose of the administered drug, despite the apparent achievement of a therapeutic effect.

The basic principles of etiotropic treatment are reduced to the isolation and identification of the causative agent of an infectious disease, the study of its sensitivity to drugs, the choice of the active and least toxic etiotropic drug (or several drugs in combined treatment), determining its optimal doses, method and duration of use, taking into account possible side effects . Since the timeliness of treatment is extremely important, it is often started immediately after taking the material for microbiological examination, even before the pathogen is isolated. At the same time, it is advisable to avoid prescribing a multitude of medicines and medical procedures, their volume should be limited to the minimum necessary in each specific case.

In infectious practice, antibiotics are widely used. Preparations of the penicillin group (salts of benzylpenicillin, phenoxymethylpenicillin, bicillin ♠, ampicillin, semi-synthetic penicillins - oxacillin, ampicillin, carbenicillin, etc.) have a bactericidal effect against cocci (causative agents of meningococcal infection, pneumonia, erysipelas), as well as pathogens of diphtheria, leptospirosis, Siberian ulcers, listeriosis. Penicillins resistant to acids and the action of β-lactamases (cloxacillin Ψ, dicloxacillin Ψ, flucloxacillin Ψ) are used for

oral administration. Cephalosporins I-IV generations are distinguished by a pronounced bactericidal effect against gram-positive (staphylococci and pneumococci), as well as most gram-negative bacteria. The preparations are of low toxicity, but at the same time they can sometimes cause undesirable manifestations in the form of allergic and dyspeptic reactions, hemorrhagic syndrome, phlebitis (when administered parenterally). The carbapenems (imipenem, meropenem) belonging to the reserve antibiotics have the widest spectrum of antimicrobial activity. Tetracycline, chloramphenicol ♠, rifampicin are used in the treatment of yersiniosis, rickettsiosis (typhus, Brill-Zinsser disease, Q fever, etc.), borreliosis, typhoid fever and paratyphoid fever, brucellosis, legionellosis, as well as chlamydia and mycoplasmosis. With resistance of pathogens to penicillin, levomycetin ♠ and tetracyclines, aminoglycosides of various generations are used - streptomycin, neomycin, kanamycin, monomycin ♠ (I generation), gentamicin, tobramycin, sisomycin (II generation), netilmicin, amikacin (III generation), etc., however their spectrum of action does not capture the anaerobic flora, and the toxicity is much higher, and therefore it is currently prohibited to prescribe drugs of the first generation orally. Aminoglycosides are active against gram-negative flora, staphylococci, Pseudomonas aeruginosa (preparations of II-III generations). With coccal infections, as well as whooping cough, diphtheria and campylobacteriosis, macrolides (erythromycin, oleandomycin, etc.) are prescribed. One of the best semi-synthetic macrolides in terms of its pharmacological properties is azithromycin. In cases of fungal diseases, antifungal antibiotics are active - nystatin, mycoseptin ♠, etc.

The number of new antibiotics is constantly growing. Many drugs of natural origin are being replaced by semi-synthetic antibiotics of III and IV generations, which have numerous advantages. However, it should be remembered that the widespread and unreasonable use of antibiotics, long courses of antibiotic therapy can cause undesirable consequences: the development of sensitization with allergic reactions, dysbiosis (dysbacteriosis), a decrease in the activity of the immune system, an increase in the resistance of pathogenic strains of microorganisms, and many others.

A relatively new group of drugs for the etiotropic treatment of infectious diseases - fluoroquinolones. They are increasingly used in cases of severe forms of intestinal bacterial infections (typhoid fever, yersiniosis), mycoplasmosis and chlamydia.

When carrying out etiotropic treatment, other antimicrobial agents are also prescribed, to a lesser extent than antibiotics that cause the development of resistance of microorganisms. In the treatment of pneumonia, tonsillitis and some other infectious diseases, sulfanilamide preparations, especially of prolonged action, can be used. Their appointment in combination with antibiotics often gives a synergistic therapeutic effect. At the same time, the use of sulfonamides can cause adverse reactions: sensitization of the body, inhibition of hematopoiesis, suppression of normal microflora, the formation of stones in the urinary organs, and irritant effects on the mucous membranes.

Nitrofuran derivatives (furazolidone, furadonin ♠, furagin ♠, etc.) are effective in the treatment of many bacterial and protozoal diseases, including

including those caused by antibiotic-resistant flora. They have found application in the treatment of giardiasis, trichomoniasis, amoebiasis.

Antiviral drugs are increasingly being introduced into the practice of treating infectious diseases. They are used in etiotropic therapy and prevention of influenza (amantadine, rimantadine ♠), herpes infection (acyclovir, etc.), viral hepatitis (ribavirin), HIV infection (azidothymidine Ψ). However, the clinical efficacy of these drugs in many cases remains insufficiently high.

In the chronic course of the disease, adherence to treatment is of particular importance, that is, strict adherence to regular medication, which in some cases is carried out for life (for example, with HIV infection). HIV-infected persons who constantly use antiretroviral therapy remain healthy and able to work for many years.

Drugs are also used in the treatment of infectious diseases. specific immunotherapy- immune sera (see Annexes, Table 3), immunoglobulins and γ-globulins, plasma of immunized donors. Immune sera are divided into antitoxic and antimicrobial. Antitoxic sera are represented by antidiphtheria, antitetanus, antibotulinum and antigangrenous sera of various types. They contain specific antitoxic antibodies, they are used to neutralize pathogen toxins freely circulating in the blood in the relevant diseases. The clinical effect of the use of antitoxic sera is most pronounced in the early stages of the disease, since sera are not able to neutralize toxins already bound by cells and tissues. Antimicrobial sera contain antibodies to pathogenic pathogens; they are rarely used in infectious practice (anti-anthrax globulin).

In the treatment of many infectious diseases (influenza, measles, leptospirosis, herpes infection, anthrax, etc.), immunoglobulins with a high concentration of antibodies, as well as plasma from immunized donors (antistaphylococcal, antipseudomonal, etc.), have been used.

Currently, killed vaccines are used more and more limitedly due to the possibility of developing adverse reactions to the ballast substances contained in them, autoimmune reactions, an immunosuppressive effect, and an increase in disease relapses.

The use of specific immunotherapy drugs requires medical supervision and strict adherence to the rules set forth in the instructions for their use, since in some cases it can lead to the development of complications:

Anaphylactic shock;

serum sickness;

Double anaphylactic reaction.

Anaphylactic shock - an allergic reaction of the immediate type that occurs in persons with hypersensitivity. Its main pathogenetic mechanisms include the formation of immune complexes that are fixed on cellular structures with their subsequent damage and the release of biologically active substances. The latter, acting on the smooth muscles of blood vessels and bronchi, lead to the development of vascular paralysis with an increase in the permeability of the walls of blood vessels, spasm of the smooth muscles of organs. This reduces the volume of circulating blood and cardiac output. Severe complications develop in the form of acute vascular insufficiency, disseminated intravascular coagulation syndrome (DIC), cerebral and pulmonary edema, laryngeal edema with asphyxia, acute renal failure and (or) acute adrenal insufficiency.

Anaphylactic shock occurs suddenly, immediately after parenteral administration of the drug, and is characterized by a rapid, often lightning-fast course.

Clinical signs of anaphylactic shock:

General anxiety of the patient;

Feeling of fear;

Headache;

Dizziness;

feeling of heat;

Hyperemia;

Puffiness of the face;

Nausea and vomiting;

General weakness.

There is a feeling of pressure in the chest, pain in the heart. Shortness of breath progresses rapidly, breathing is noisy, wheezing, with difficulty in inhaling and exhaling. There may be attacks of suffocation with coughing. Quincke's edema, urticaria are sometimes observed. At the same time, the skin becomes pale, sweating increases, blood pressure drops, tachycardia increases, consciousness is disturbed. With a more gradual development of a state of shock, patients note itching, numbness of the lips, tongue, face.

Emergency care for anaphylactic shock is provided on the spot.

It includes the following steps.

Immediately stop the administration of the drug that caused the anaphylactic reaction.

Apply a tourniquet above the injection site.

Chop the injection site with diluted epinephrine ♠ (1 ml of 0.1% adrenaline ♠ diluted in 5-10 ml of isotonic sodium chloride solution).

Apply ice to the injection site.

Give the patient a horizontal position with legs slightly raised and head turned to one side.

Put a heating pad on your feet.

Apply a tonometer cuff, record the time, measure and record blood pressure, pulse, respiration.

Inject intravenously 0.5-1 ml of 0.1% solution of adrenaline ♠ in 10-20 ml of isotonic sodium chloride solution and 60 mg of prednisolone. To repeat

introduction of adrenaline ♠ intravenously every 10-20 minutes until the patient is taken out of shock or, if there is no effect, carry out an intravenous drip infusion (1-2 ml of a 0.1% solution of adrenaline ♠ in 250 ml of isotonic glucose solution ♠).

In case of bronchospasm and pulmonary edema, inject 0.5 ml of a 0.1% solution of atropine sulfate ♠ subcutaneously, intramuscularly - 1 ml of a 2.5% solution of diprazine ♠, intravenously - 20 ml of a 40% glucose solution ♠ with 60 mg of prednisolone.

Carry out infusion with intravenous drip injection of 400 ml of rheopolyglucin ♠, 400 ml of isotonic sodium chloride solution. Add 5,000 action units (U) of heparin in dextran solution ♠, prednisone at the rate of 10 mg/kg (the entire dose is administered fractionally over 2 hours), 2 ml of a 0.25% solution of droperidol, 1 ml of a 0.05% solution strophanthin.

Subcutaneously inject 2 ml of 10% caffeine solution, 2 ml of 25% cordiamine solution ♠.

Continually supply oxygen throughout the treatment.

The severe course of anaphylactic shock often determines the need for a set of measures in the intensive care unit:

anticonvulsant treatment;

Correction of violations of water-electrolyte metabolism and acid-base balance;

intubation or tracheostomy;

IVL, etc.

Serum sickness develops 6-12 days after serum administration. It is manifested by a febrile reaction, the occurrence of a maculopapular rash on the skin, swelling of the mucous membranes, and lymphadenitis.

Double anaphylactic reaction proceeds in 2 stages:

First, anaphylactic shock develops;

Then - serum sickness.

plays an important role in the treatment of certain infections nonspecific immunotherapy. Her arsenal includes normal human immunoglobulin, immunostimulants and immunosuppressants. They are prescribed to increase the nonspecific resistance of the body and the regulatory effect on the immune system. In the treatment of a number of viral infections (influenza, viral encephalitis, herpes infection), IFN and stimulants of their production are used.

Pentoxyl ♠, methyluracil ♠ and potassium orotate are also used to stimulate leukopoiesis. Splenin ♠ and apilac ♠ speed up recovery after severe infections.

Immunomodulators levamisole, thymalin ♠, T-activin ♠, sodium nucleinate and some lipopolysaccharides (pyrogenal ♠, prodigiosan ♠) contribute to the regulation of cellular immunity and phagocytosis.

It is necessary to pay attention to the fact that indications for prescribing drugs of this group are determined by a whole complex of various factors:

Features of the pathogenesis of the disease;

timing and severity of illness;

The state of nonspecific and specific body defense factors.

Therefore, the use of immunotropic drugs is recommended only under dynamic immunological control.

Pathogenetic treatment aimed at correcting homeostasis disorders in infectious diseases.

Its methods and means are based on a detailed study of pathogenetic mechanisms:

intoxication;

Violations of water-electrolyte metabolism and acid-base balance;

Changes in the rheological properties of blood;

microcirculation;

immune status, etc.

One of the main areas of pathogenetic treatment of infectious diseases is the use of drugs that reduce intoxication. Colloidal solutions - hemodez ♠, polydez ♠, rheopolyglucin ♠, macrodex Ψ, gelatinol ♠, albumin and many others, administered intravenously by drip in average doses of 200 to 400 ml, have pronounced detoxification properties. The detoxification effect of 5% or 10% glucose solution ♠, 0.9% sodium chloride solution is less pronounced. In the treatment of acute intestinal infections accompanied by diarrhea, detoxification can be enhanced with simultaneous administration of intravenous infusions and oral administration of non-steroidal anti-inflammatory drugs (indomethacin) and enterosorbents (enterodesis ♠, polysorb ♠, activated charcoal, etc.). Simultaneously with detoxification, saluretics (furosemide, lasix ♠, etc.) are prescribed to improve the excretory ability of the kidneys.

In severe infectious diseases, extracorporeal detoxification methods are used:

Hemodialysis;

hemosorption;

Plasmapheresis;

Cytopheresis.

Indispensable drugs for the correction of dehydration, acid-base balance, rheological and microcirculatory disorders are polyionic crystalloid isotonic solutions for intravenous infusions (trisol ♠, quartasol ♠, lactasol Ψ, etc.) and glucose-salt solutions for oral administration (rehydron ♠, oralit Ψ, citroglucosolan Ψ ). Their use simultaneously helps to reduce intoxication, since the use of colloidal solutions under dehydration conditions is contraindicated. The activity of the multidirectional action of this group of drugs (rehydration and detoxification) is potentiated in acute intestinal infections by the simultaneous administration of inhibitors of prostanoid biosynthesis (indomethacin).

To prevent pronounced manifestations of inflammation and allergies in many infectious diseases (encephalitis, meningitis, infectious mononucleosis, brucellosis, trichinosis, etc.), antihistamines and glucocorticoids (prednisolone, dexamethasone, hydrocortisone, etc.) are prescribed. Hormonal preparations are especially indicated in cases of TSS and the development of acute adrenal insufficiency (meningococcal infection, diphtheria), as well as in anaphylactic shock.

Infectious diseases, especially intestinal infections, often complicate the development of dysbiosis (dysbacteriosis), which is greatly facilitated by active and long-term, but necessary antibiotic treatment.

In the correction of dysbiosis, probiotics are widely used, i.e. bacterial preparations that restore and regulate the intestinal microflora (colibacterin ♠, bifidumbacterin ♠, lactobacterin ♠, bactisubtil ♠, etc.), and prebiotics (substances of non-microbial origin).

Regulation of the processes of proteolysis, fibrinolysis, depolymerization in the pathogenetic treatment of infectious diseases is carried out by the appointment of enzyme preparations. In recent years, trypsin, chymotrypsin, fibrinolysin, streptodecase ♠, ε-aminocaproic acid, deoxyribonuclease ♠, etc. have been widely used. complicated course of acute viral hepatitis). The need to correct violations of the secretion of the gastrointestinal glands explains the feasibility of using pancreatin, festal ♠, panzinorm ♠, mezim ♠, pankurmen Ψ and other enzyme preparations.

An obligatory component in the treatment of infectious patients is vitamin therapy. The lack of vitamins reduces the body's resistance and facilitates the development of an infectious process, often manifested by an increase in intoxication, the development of an unfavorable course of the disease and complications. The appointment of vitamins C and group B to infectious patients helps to normalize metabolic processes, reduce intoxication, and has a positive immunomodulatory effect.

In infectious diseases, symptomatic treatment is widely used - the appointment of cardiovascular and antispasmodic drugs, painkillers, antipyretics, sedatives, hypnotics, anticonvulsants, etc.

In severe infectious diseases and the development of complications (ITS, thrombohemorrhagic syndrome, cerebral edema, acute respiratory and cardiovascular failure, convulsive syndrome, acute liver failure and acute renal failure), intensive complex pathogenetic treatment is indicated using the above and special methods of treatment (IVL, hyperbaric oxygen therapy, etc.). Treatment is often carried out in intensive care units.

According to individual indications for infectious diseases, methods of physiotherapy and balneotherapy are used.

After many infectious diseases, dispensary observation of convalescents is recommended, as well as sanatorium treatment.

The penetration of microorganisms into the internal environment of the human body leads to a violation of the body's homeostasis, which can manifest itself as a complex of physiological (adaptive) and pathological reactions, known as an infectious process, or infection. The range of these reactions is quite wide, its extreme poles are clinically pronounced lesions and asymptomatic circulation. The term " infection"(from lat. inficio - to introduce something harmful and late lat. infectio - infection) can determine both the infectious agent itself and the fact of its entry into the body, but it is more correct to use this term to refer to the entire set of reactions between the pathogen and the host.

According to I.I. Mechnikov, "... infection is a struggle between two organisms." Domestic virologist V.D. Solovyov considered the infectious process as "a special kind of ecological explosion with a sharp increase in the interspecific struggle between the host organism and the pathogenic bacteria that have invaded it." Famous infectious disease specialists A.F. Bilibin and T.P. Rudnev (1962) defined it as a complex set of "physiological protective and pathological reactions that occur under certain environmental conditions in response to the action of pathogenic microbes."

The modern scientific definition of the infectious process was given by V.I. Pokrovsky: "The infectious process is a complex of mutual adaptive reactions in response to the introduction and reproduction of a pathogenic microorganism in a macroorganism, aimed at restoring disturbed homeostasis and biological balance with the environment."

Thus, the participants in the infectious process are the microorganism that causes the disease, the host organism (human or animal) and certain, including social, environmental conditions.

Toxigenicity of the pathogen- the ability to synthesize and isolate exo- and endotoxins. Exotoxins- proteins secreted by microorganisms in the process of life. They exhibit a specific effect, leading to selective pathomorphological and pathophysiological disorders in organs and tissues (causative agents of diphtheria, tetanus, botulism, cholera, etc.). Endotoxins released after the death and destruction of the microbial cell. Bacterial endotoxins are structural components of the outer membrane of almost all gram-negative microorganisms, biochemically representing a lipopolysaccharide complex (LPS complex). Structural and functional analysis of the LPS complex molecule showed that lipid A is the biologically active site (site) that determines all the main properties of the native LPS complex preparation. It is characterized by pronounced heterogeneity, which allows the body's defenses to recognize it. The action of endotoxins is not specific, which is manifested by similar clinical signs of the disease,

Adhesiveness and invasiveness of microorganisms- the ability to be fixed on cell membranes and penetrate into cells and tissues. These processes are facilitated by the presence of ligand-receptor structures in pathogens, a capsule that prevents absorption by phagocytes, flagella and enzymes that damage cell membranes.

So, one of the most important mechanisms for the preservation of the pathogen in the host organism is microbial persistence, which consists in the formation of atypical wallless forms of the microorganism - L-forms, or filterable forms. At the same time, a sharp restructuring of metabolic processes is observed, expressed in a slowdown or complete loss of enzymatic functions, inability to grow on elective nutrient media for the original cellular structures, and loss of sensitivity to antibiotics.

Virulence- qualitative manifestation of pathogenicity. The sign is unstable; in the same strain of the pathogen, it can change during the infectious process, including under the influence of antimicrobial therapy. In the presence of certain features of the macroorganism (immunodeficiency, violations of barrier defense mechanisms) and environmental conditions, opportunistic microorganisms and even saprophytes can become the culprits for the development of an infectious disease.

The place where a pathogen enters the human body is called gateway of infection, the clinical picture of the disease often depends on their localization. The properties of the microorganism and the route of its transmission determine the variety of entrance gates. They can be skin (for example, for pathogens of typhus, anthrax, malaria), mucous membranes of the respiratory tract (in particular, for the influenza virus and meningococcus), gastrointestinal tract (for example, for pathogens, dysentery), genital organs (for pathogens , HIV infection, ). With various infectious diseases, there may be one (,) or several (brucellosis,,) entrance gates. The formation of the infectious process and the severity of the clinical manifestations of an infectious disease are also significantly affected by the infectious dose of pathogens.

macroorganism- an active participant in the infectious process, which determines the possibility of its occurrence, the form of manifestation, severity, duration and outcome. The human body has a variety of congenital or individually acquired factors of protection against the aggression of a pathogenic pathogen. The protective factors of the macroorganism help to prevent an infectious disease, and if it develops, to overcome the infectious process. They are divided into nonspecific and specific.

Non-specific protective factors are very numerous and diverse in terms of the mechanisms of antimicrobial action. External mechanical barriers

For most microorganisms, intact skin and mucous membranes serve. The protective properties of the skin and mucous membranes are provided by lysozyme, secretions of the sebaceous and sweat glands, secretory, phagocytic cells, normal microflora that prevents intervention and colonization of the skin and mucous membranes by pathogenic microorganisms. An extremely important barrier in intestinal infections is the acidic environment of the stomach. Cilia of the respiratory epithelium and intestinal motility contribute to the mechanical removal of pathogens from the body. The blood-brain barrier serves as a powerful internal barrier to the penetration of microorganisms into the CNS.

Non-specific inhibitors of microorganisms include enzymes of the gastrointestinal tract, blood and other body fluids (bacteriolysins, lysozyme, properdin, hydrolases, etc.), as well as many biologically active substances [IFN, lymphokines, prostaglandins (), etc.].

Following external barriers, phagocytic cells and the complement system constitute universal forms of macroorganism protection. They serve as links between non-specific protective factors and specific immune responses. Phagocytes, represented by granulocytes and cells of the macrophage-monocyte system, not only absorb and destroy microorganisms, but also present microbial antigens to immunocompetent cells, initiating an immune response. Components of the complement system, attaching to AT molecules, provide their lysing effect on cells containing the corresponding Ag.

The most important mechanism for protecting a macroorganism from the effects of a pathogenic pathogen is the formation of immunity as a complex of humoral and cellular reactions that determine the immune response. determines the course and outcome of the infectious process, serving as one of the leading mechanisms that maintain the homeostasis of the human body.

Humoral reactions are due to the activity of AT synthesized in response to the penetration of Ag. AT are represented by immunoglobulins of various classes: IgM, IgG, IgD and IgE. In the earliest stage of the immune response, IgM are the first to form as the phylogenetically most ancient. They are active against many bacteria, especially in agglutination (RA) and lysis reactions. Significant IgG titers appear on the 7-8th day after the action of the antigenic stimulus. However, with repeated exposure to Ag, they are formed already on the 2-3rd day, which is due to the formation of immunological memory cells in the dynamics of the primary immune response. In the secondary immune response, the IgG titer significantly exceeds the IgM titer. In the form of monomers, they circulate in the blood and tissue fluids, but IgA dimers are of particular importance, which are responsible for immune reactions on the mucous membranes, where they neutralize microorganisms and their toxins. Therefore, they are also called secretory AT, since they are mainly found not in blood serum, but in the secrets of the gastrointestinal tract, respiratory and genital tracts. They play a particularly important role in intestinal infections and. The protective functions of IgD and IgE are not fully understood. It is known that IgE is involved in the development of allergic reactions.

The specificity of AT is due to their strict correspondence with the Ag of the pathogen that caused their formation, and interaction with them. However, antibodies can also react with antigens of other microorganisms that have a similar antigenic structure (common antigenic determinants).

Unlike humoral reactions, which are realized through AT circulating in body media, cellular immune reactions are realized through the direct participation of immunocompetent cells.

Regulation of the immune response is carried out at the genetic level (genes of immunoreactivity).

The environment, as the third component of the infectious process, affects its occurrence and the nature of the course, affecting both the micro- and the macroorganism. Temperature, humidity and dustiness of the air, solar radiation, antagonism of microorganisms and other numerous natural environmental factors determine the viability of pathogenic pathogens and affect the reactivity of the macroorganism, reducing its resistance to many infections. The social factors of the external environment are extremely important: the deterioration of the ecological situation and living conditions of the population, malnutrition, stressful situations in connection with socio-economic and military conflicts, the state of healthcare, the availability of qualified medical care, etc.

Forms of the infectious process can be different depending on the properties of the pathogen, the conditions of infection and the initial state of the macroorganism. Until now, not all of them have been sufficiently studied and clearly characterized.

Transient (asymptomatic, "healthy") carriage- a single ("accidental") detection in the human body of a pathogenic (or any other) microorganism in tissues that are considered sterile (for example, in the blood). The fact of transient carriage is determined in a series of sequential bacteriological tests. At the same time, the currently existing examination methods do not allow to identify clinical, pathological and laboratory signs of the disease.

The carriage of pathogenic microorganisms is possible at the stage of recovery from an infectious disease (convalescent carriage). It is characteristic of a number of viral and bacterial infections. Depending on the duration, convalescent carriage is divided into acute (up to 3 months after clinical recovery) and chronic (over 3 months). As a rule, in these cases, carriage is asymptomatic or occasionally manifests itself at the subclinical level, but may be accompanied by the formation of functional and morphological changes in the body, the development of immune responses.

inapparent form. One of the forms of the infectious process, characterized by the absence of clinical manifestations of the disease, but accompanied by

an increase in specific AT titers as a result of the development of immune reactions to the pathogen Ag.

Manifest forms of the infectious process constitute an extensive group of infectious diseases caused by exposure to the human body of various microorganisms - bacteria, viruses, protozoa and fungi. For the development of an infectious disease, it is not enough just to introduce a pathogenic pathogen into the human body. The macroorganism must be susceptible to this infection, respond to the pathogen with the development of pathophysiological, morphological, protective, adaptive and compensatory reactions that determine the clinical and other manifestations of the disease. At the same time, the micro- and macroorganism interact in certain, including socio-economic, environmental conditions that inevitably affect the course of an infectious disease.

The division of diseases into infectious and non-infectious is rather conditional. Basically, it is traditionally based on two criteria characteristic of the infectious process: the presence of the pathogen and the contagiousness (infectiousness) of the disease. But at the same time, a mandatory combination of these criteria is not always observed. For example, the causative agent of erysipelas - () - hemolytic group A streptococcus - also causes the development of non-contagious glomerulonephritis, dermatitis, rheumatic process and other diseases, and erysipelas itself, as one of the forms of streptococcal infection, is considered practically non-contagious. Therefore, the treatment of infectious diseases is faced not only by infectious disease specialists, but also by representatives of almost all clinical specialties. Apparently, most human diseases could be classified as infectious. The creation of an infectious disease service, historically established as a result of the development of specialization in medicine, is intended to provide qualified assistance to infectious patients at the pre-hospital (at home), hospital (in a hospital) and dispensary (observation after discharge from a hospital) stages.

The nature, activity and duration of the clinical manifestations of an infectious disease, which determine the degree of its severity, can be extremely diverse. With a typical overt infection, the clinical signs and general features that are most characteristic of an infectious disease are clearly expressed: the sequence of changing periods, the possibility of developing exacerbations, relapses and complications, acute, fulminant (fulminant), protracted and chronic forms, the formation of immunity. The severity of overt infections can be different - mild, moderate or severe.

Some viruses and prions cause a special form of disease known as slow infections. They are characterized by a multi-month or even long-term, slow, but steadily progressive course, a complex of peculiar lesions of individual organs and systems, the development of oncological pathology, and an inevitable death.

Atypical overt infections can occur as erased, latent and mixed infections. An erased (subclinical) infection is a variant of the manifest form, in which the clinical signs of the disease and the change in its periods are not clearly expressed, often minimally, and the immunological reactions are incomplete. Diagnosis of an erased infection causes significant difficulties, which contributes to the prolongation of an infectious disease.

Perhaps the simultaneous occurrence of two infectious diseases caused by different pathogens. In such cases, they speak of a mixed infection, or mixed infection.

The development of an infectious disease may be due to the dissemination of pathogenic pathogens that were previously in the human body in the form of a “dormant” latent focus of infection, or the activation of opportunistic and even normal flora inhabiting the skin and mucous membranes. Such diseases are known as endogenous infections (autoinfections). As a rule, they develop against the background of immunodeficiencies associated with a variety of reasons - severe somatic diseases and surgical interventions, the use of toxic drugs, radiation and hormone therapy, HIV infection.

It is possible to re-infect with the same pathogen with the subsequent development of the disease (usually in a manifest form). If such infection occurred after the end of the primary infectious process, it is defined by the term reinfection. From reinfections and, especially, mixed infections should be distinguished superinfection arising from infection with a new infectious agent against the background of an already existing infectious disease.

Infection is the penetration and reproduction of a pathogenic microorganism (bacteria, virus, protozoan, fungus) in a macroorganism (plant, fungus, animal, human) that is susceptible to this type of microorganism. A microorganism capable of infection is called an infectious agent or pathogen.

Infection is, first of all, a form of interaction between a microbe and an affected organism. This process is extended in time and proceeds only under certain environmental conditions. In an effort to emphasize the temporal extent of infection, the term "infectious process" is used.

Infectious diseases: what are these diseases and how do they differ from non-communicable diseases

Under favorable environmental conditions, the infectious process takes on the extreme degree of its manifestation, in which certain clinical symptoms appear. This degree of manifestation is called an infectious disease. Infectious diseases differ from non-infectious pathologies in the following ways:

• The cause of the infection is a living microorganism. The microorganism that causes a particular disease is called the causative agent of that disease;
• Infections can be transmitted from an affected organism to a healthy one - this property of infections is called contagiousness;
• Infections have a latent (latent) period - this means that they do not appear immediately after the pathogen enters the body;
• Infectious pathologies cause immunological changes - they excite an immune response, accompanied by a change in the number of immune cells and antibodies, and also cause infectious allergies.

Rice. 1. Assistants of the famous microbiologist Paul Ehrlich with laboratory animals. At the dawn of the development of microbiology, a large number of animal species were kept in laboratory vivariums. Now often limited to rodents.

Infectious disease factors

So, for the occurrence of an infectious disease, three factors are necessary:

1. pathogen microorganism;
2. The host organism susceptible to it;
3. The presence of such environmental conditions in which the interaction between the pathogen and the host leads to the onset of the disease.

Infectious diseases can be caused by opportunistic microorganisms, which are most often representatives of the normal microflora and cause the disease only when the immune defense is reduced.

Rice. 2. Candida - part of the normal microflora of the oral cavity; they cause disease only under certain conditions.

And pathogenic microbes, being in the body, may not cause a disease - in this case, they speak of the carriage of a pathogenic microorganism. In addition, laboratory animals are far from always susceptible to human infections.

For the occurrence of an infectious process, a sufficient number of microorganisms that enter the body, which is called the infectious dose, is also important. The susceptibility of the host organism is determined by its biological species, sex, heredity, age, nutritional adequacy and, most importantly, the state of the immune system and the presence of concomitant diseases.

Rice. 3. Plasmodium malaria can spread only in those territories where their specific carriers live - mosquitoes of the genus Anopheles.

Environmental conditions are also important, in which the development of the infectious process is maximally facilitated. Some diseases are characterized by seasonality, a number of microorganisms can only exist in a certain climate, and some require vectors. Recently, the conditions of the social environment have come to the fore: economic status, living and working conditions, the level of development of health care in the state, and religious characteristics.

Infectious process in dynamics

The development of infection begins with an incubation period. During this period, there are no manifestations of the presence of an infectious agent in the body, but infection has already occurred. At this time, the pathogen multiplies to a certain number or releases a threshold amount of the toxin. The duration of this period depends on the type of pathogen.

For example, with staphylococcal enteritis (a disease that occurs when eating contaminated food and is characterized by severe intoxication and diarrhea), the incubation period takes from 1 to 6 hours, and with leprosy it can stretch for decades.

Rice. 4. The incubation period of leprosy can last for years.

In most cases, it lasts 2-4 weeks. Most often, the peak of infectivity occurs at the end of the incubation period.

The prodromal period is the period of precursors of the disease - vague, non-specific symptoms, such as headache, weakness, dizziness, change in appetite, fever. This period lasts 1-2 days.

Rice. 5. Malaria is characterized by fever, which has special properties in various forms of the disease. The shape of the fever suggests the type of Plasmodium that caused it.

The prodrome is followed by the peak of the disease, which is characterized by the appearance of the main clinical symptoms of the disease. It can develop both rapidly (then they talk about an acute onset), or slowly, sluggishly. Its duration varies depending on the state of the body and the capabilities of the pathogen.

Rice. 6. Typhoid Mary, who worked as a cook, was a healthy carrier of typhoid bacilli. She infected more than 500 people with typhoid fever.

Many infections are characterized by an increase in temperature during this period, associated with the penetration into the blood of the so-called pyrogenic substances - substances of microbial or tissue origin that cause fever. Sometimes the rise in temperature is associated with the circulation in the bloodstream of the pathogen itself - this condition is called bacteremia. If at the same time the microbes also multiply, they speak of septicemia or sepsis.

Rice. 7. Yellow fever virus.

The end of the infectious process is called the outcome. The following options exist:

• Recovery;
• Lethal outcome (death);
• Transition to a chronic form;
• Relapse (recurrence due to incomplete cleansing of the body from the pathogen);
• The transition to a healthy microbe carrier (a person, without knowing it, carries pathogenic microbes and in many cases can infect others).

Rice. 8. Pneumocysts are fungi that are the leading cause of pneumonia in immunocompromised people.

Classification of infections

Rice. 9. Oral candidiasis is the most common endogenous infection.

By the nature of the pathogen, bacterial, fungal, viral and protozoal (caused by protozoa) infections are isolated. According to the number of pathogen types, there are:

• Monoinfections - caused by one type of pathogen;
• Mixed, or mixed infections - caused by several types of pathogens;
• Secondary - arising against the background of an already existing disease. A special case is opportunistic infections caused by opportunistic microorganisms against the background of diseases accompanied by immunodeficiencies.

According to their origin, they are:

• Exogenous infections, in which the pathogen penetrates from the outside;
• Endogenous infections caused by microbes that were in the body before the onset of the disease;
• Autoinfections - infections in which self-infection occurs by transferring pathogens from one place to another (for example, oral candidiasis caused by the introduction of a fungus from the vagina with dirty hands).

According to the source of infection, there are:

• Anthroponoses (source - man);
• Zoonoses (source - animals);
• Anthroposoonoses (the source can be either a person or an animal);
• Sapronoses (source - environmental objects).

According to the localization of the pathogen in the body, local (local) and general (generalized) infections are distinguished. According to the duration of the infectious process, acute and chronic infections are distinguished.

Rice. 10. Mycobacterium leprosy. Leprosy is a typical anthroponosis.

The pathogenesis of infections: a general scheme for the development of the infectious process

Pathogenesis is a mechanism for the development of pathology. The pathogenesis of infections begins with the penetration of the pathogen through the entrance gate - mucous membranes, damaged integuments, through the placenta. Further, the microbe spreads throughout the body in various ways: through the blood - hematogenously, through the lymph - lymphogenously, along the nerves - perineurally, along the length - destroying the underlying tissues, along the physiological paths - along, for example, the digestive or genital tract. The place of the final localization of the pathogen depends on its type and affinity for a particular type of tissue.

Having reached the place of final localization, the pathogen has a pathogenic effect, damaging various structures mechanically, by waste products or by releasing toxins. Isolation of the pathogen from the body can occur with natural secrets - feces, urine, sputum, purulent discharge, sometimes with saliva, sweat, milk, tears.

epidemic process

The epidemic process is the process of the spread of infections among the population. Links of the epidemic chain include:

• Source or reservoir of infection;
• transmission path;
• susceptible population.

Rice. 11. Ebola virus.

The reservoir differs from the source of infection in that the pathogen accumulates in it between epidemics, and under certain conditions it becomes a source of infection.

The main ways of transmission of infections:

1. Fecal-oral - with food contaminated with infectious secretions, hands;
2. Airborne - through the air;
3. Transmissive - through a carrier;
4. Contact - sexual, by touching, by contact with infected blood, etc.;
5. Transplacental - from a pregnant mother to a child through the placenta.

Rice. 12. H1N1 influenza virus.

Transmission factors - objects that contribute to the spread of infection, for example, water, food, household items.

According to the coverage of the infectious process of a certain territory, there are:

• Endemic - infections "tied" to a limited area;
• Epidemics - infectious diseases covering large areas (city, region, country);
• Pandemics are epidemics that have the scale of several countries and even continents.

Infectious diseases make up the lion's share of all diseases that humanity faces. They are special in that with them a person suffers from the vital activity of living organisms, albeit thousands of times smaller than himself. Previously, they often ended fatally. Despite the fact that today the development of medicine has significantly reduced mortality in infectious processes, it is necessary to be alert and aware of the features of their occurrence and development.