infectious process. Definitions of the concepts "infection", "infectious process", "infectious disease" The term "Infection" (lat. Infectio - infection) - - presentation. Infectious process and infectious diseases

The environment is filled with a huge number of "inhabitants", among which there are various microorganisms: viruses, bacteria, fungi, protozoa. They can live in absolute harmony with a person (non-pathogenic), exist in the body without causing harm under normal conditions, but become more active under the influence of certain factors (conditionally pathogenic) and be dangerous to humans, causing the development of a disease (pathogenic). All these concepts relate to the development of the infectious process. What is an infection, what are its types and features - discussed in the article.

Basic concepts

An infection is a complex of relationships between various organisms, which has a wide range of manifestations - from asymptomatic carriage to the development of the disease. The process appears as a result of the introduction of a microorganism (virus, fungus, bacterium) into a living macroorganism, in response to which a specific protective reaction occurs on the part of the host.

Features of the infectious process:

1. Contagiousness - the ability to quickly spread from a sick person to a healthy one.
2. Specificity - a certain microorganism causes a specific disease, which has its characteristic manifestations and localization in cells or tissues.
3. Periodicity - each infectious process has periods of its course.

Periods

The concept of infection is also based on the cyclic nature of the pathological process. The presence of periods in development is characteristic of each similar manifestation:

1. The incubation period is the time that passes from the moment the microorganism enters the body of a living being until the first clinical signs of the disease appear. This period can last from a few hours to several years.
2. The prodromal period is the appearance of a general clinic characteristic of most pathological processes (headache, weakness, fatigue).
3. Acute manifestations - the peak of the disease. During this period, specific symptoms of infection develop in the form of rashes, characteristic temperature curves, tissue damage at the local level.
4. Reconvalescence is the time when the clinical picture fades and the patient recovers.

Types of infectious processes

To consider in more detail the question of what an infection is, you need to understand what it is. There are a significant number of classifications depending on the origin, course, localization, number of microbial strains, etc.

1. According to the method of penetration of pathogens:

• exogenous process - characterized by the penetration of a pathogenic microorganism from the external environment;
• endogenous process - there is an activation of own conditionally pathogenic microflora under the influence of adverse factors.

2. By origin:

• spontaneous process - characterized by the absence of human intervention;
• experimental - the infection is bred artificially in the laboratory.

3. By the number of microorganisms:

• monoinfection - caused by one type of pathogen;
• mixed - several types of pathogens are involved.

4. By order:

• the primary process is a newly appeared disease;
• secondary process - accompanied by the addition of an additional infectious pathology against the background of a primary disease.

5. By localization:

• local form - the microorganism is located only in the place through which it entered the host organism;
• generalized form - pathogens spread throughout the body with further settling in certain favorite places.

6. Downstream:

• acute infection - has a vivid clinical picture and lasts no more than a few weeks;
• chronic infection - characterized by a sluggish course, can last for decades, has exacerbations (relapses).

7. By age:

• "Children's" infections - affect children mainly aged 2 to 10 years (chicken pox, diphtheria, scarlet fever, whooping cough);
• there is no concept of "adult infections" as such, since the children's body is also sensitive to those pathogens that cause the development of the disease in adults.

There are concepts of reinfection and superinfection. In the first case, a person who has fully recovered, after an illness, becomes infected again with the same pathogen. With superinfection, re-infection occurs even during the course of the disease (pathogen strains overlap each other).

Entry routes

There are the following ways of penetration of microorganisms, which ensure the transfer of pathogens from the external environment into the host organism:

• fecal-oral (consists of alimentary, water and contact household);
• transmissible (blood) - includes sexual, parenteral and through insect bites;
• aerogenic (air-dust and air-drop);
• contact-sexual, contact-wound.

Most pathogens are characterized by the presence of a specific route of penetration into the macroorganism. If the transmission mechanism is interrupted, the disease may not appear at all or worsen in its manifestations.

Localization of the infectious process

Depending on the affected area, the following types of infections are distinguished:

1. Intestinal. The pathological process occurs in the gastrointestinal tract, the pathogen penetrates the fecal-oral route. These include salmonellosis, dysentery, rotavirus, typhoid fever.
2. Respiratory. The process occurs in the upper and lower respiratory tract, microorganisms "move" in most cases through the air (influenza, adenovirus infection, parainfluenza).
3. Outdoor. Pathogens contaminate mucous membranes and skin, causing fungal infections, scabies, microsporia, STDs.
4. Blood. The infection enters through the blood, spreading further throughout the body (HIV infection, hepatitis, diseases associated with insect bites).

Intestinal infections

Consider the features of pathological processes on the example of one of the groups - intestinal infections. What is an infection that affects the human gastrointestinal tract, and how is it different?

Diseases of the presented group can be caused by pathogens of bacterial, fungal and viral origin. Viral microorganisms that can penetrate into various parts of the intestinal tract are rotaviruses and enteroviruses. They are able to spread not only by the fecal-oral route, but also by airborne droplets, affecting the epithelium of the upper respiratory tract and causing herpes sore throat.

Bacterial diseases (salmonellosis, dysentery) are transmitted exclusively by the fecal-oral route. Infections of fungal origin occur in response to internal changes in the body that occur under the influence of prolonged use of antibacterial or hormonal drugs, with immunodeficiency.

Rotaviruses

Rotavirus intestinal infection, the treatment of which should be comprehensive and timely, in principle, like any other disease, accounts for half of the clinical cases of viral intestinal infectious pathologies. An infected person is considered dangerous to society from the end of the incubation period until full recovery.

Rotavirus intestinal infection in children is much more severe than in adults. The stage of acute manifestations is accompanied by the following clinical picture:

• abdominal pain;
• diarrhea (the stool is light in color, there may be blood impurities);
• bouts of vomiting;
• hyperthermia;
• runny nose;
• inflammatory processes in the throat.

Rotavirus intestinal infection in children in most cases is accompanied by outbreaks of the disease in school and preschool institutions. By the age of 5, most babies have experienced the effects of rotaviruses on themselves. The following infections are not as difficult as the first clinical case.

Surgical infection

Most patients requiring surgical intervention are interested in the question of what a surgical-type infection is. This is the same process of interaction of the human body with a pathogenic agent, which only occurs against the background of an operation or requires surgical intervention to restore functions in a certain disease.

Distinguish acute (purulent, putrefactive, specific, anaerobic) and chronic process (specific, nonspecific).

Depending on the localization of the surgical infection, diseases are distinguished:

• soft tissues;
• joints and bones;
• the brain and its structures;
• abdominal organs;
• organs of the chest cavity;
• pelvic organs;
• individual elements or organs (mammary gland, hand, foot, etc.).

Causative agents of surgical infection

Currently, the most frequent "guests" of acute purulent processes are:

• staphylococcus;
• Pseudomonas aeruginosa;
• enterococcus;
• coli;
• streptococcus;
• Proteus.

The entrance gates of their penetration are various damage to the mucous membranes and skin, abrasions, bites, scratches, gland ducts (sweat and sebaceous). If a person has chronic foci of accumulation of microorganisms (chronic tonsillitis, rhinitis, caries), then they cause the spread of pathogens throughout the body.

Infection treatment

At the heart of getting rid of the pathological microflora is etiotropic therapy aimed at eliminating the cause of the disease. Depending on the type of pathogen, the following groups of medicines are used:

1. Antibiotics (if the causative agent is a bacterium). The choice of a group of antibacterial agents and a specific drug is made on the basis of bacteriological examination and determination of the individual sensitivity of the microorganism.
2. Antiviral (if the pathogen is a virus). In parallel, drugs are used that strengthen the defenses of the human body.
3. Antimycotic agents (if the pathogen is a fungus).
4. Anthelmintic (if the pathogen is a helminth or the simplest).

Treatment of infections in children under 2 years of age is carried out in a hospital to avoid the development of possible complications.

Conclusion

After the onset of a disease that has a specific pathogen, the specialist differentiates and determines the need for hospitalization of the patient. Be sure to indicate the specific name of the disease in the diagnosis, and not just the word "infection". The case history, which is taken for inpatient treatment, contains all the data on the stages of diagnosis and treatment of a specific infectious process. If there is no need to hospitalize the patient, all such information is recorded in the outpatient card.

Infection

In 1546, Girolamo Fracastoro introduced the term "infection" into medicine.

The science of infection is called infectology. This is a science that studies the infectious process, infectious disease, infectious pathology resulting from the competitive interaction of the body with pathogenic or opportunistic pathogens (infectogens), and developing methods for diagnosing, treating and preventing infectious diseases. Infectology as a systemic medical science is related to or affects in one way or another all other branches of medicine.

Lesions of organs and systems (infectious and inflammatory processes: - itis), caused by infectology - often should be differentiated from other disciplines - systemic. as it progresses - with toxicology, oncology, hematology (secondary immunodeficiencies with radiation sickness, leukemia, with damage to the thymus, spleen and bone marrow, with vitamin deficiency: berry berry, pellagra, night blindness) and endocrinology (secondary infectious complications in diabetes mellitus , hypothyroidism), metabolic syndromes - such as uremia, liver failure, cirrhosis of the liver, multiple organ failure.

General infectology is often differentiated from general diseases and local inflammatory processes (tonsillitis, otitis media, sinusitis) from purulent-septic surgery (Phlegmon, Empyema, abscesses) and gangreous-necrotic surgery (pulmonary gangrene / pneumonia, decurable ulcer) that they give.

Conditions, pathologies and diseases, and infectious and inflammatory processes are often differentiated by toxic processes, pathologies and conditions (Methods of detoxification and detoxification of the body often overlap), with hematological (Hematogenous immunodeficiencies, aplastic anemia, infectious complications in hemablastoses), with diseases caused by disorders exchange, with endocrine (metabolic diarrhea in pancreatogenic fermentopathy, uremic enteritis, secondary metabolic immunodeficiencies against the background of renal, hepatic insufficiency, against the background of diabetes mellitus and their infectious complications, vitamin deficiency: scurvy) and oncology (the last variant of the differential diagnosis is the most difficult to implement task in modern medicine, but these mistakes can cost the patient's life).

Most often, gastrointestinal forms of acute infections should be differentiated from abdominal or coloproctorectal in the form of acute poisoning and intoxication of infectious genesis should be differentiated from intoxications of non-infectious genesis - toxic (with foodborne toxic infections, botulism, infectious toxic shock), oncological (due to the similarity in the tendency to metastasis of some infectious pathogens and their ability to give tumor-like symptoms), and in some to trigger paraneoplastic, carcinogenic processes, and various metabolic syndromes.

bacterial - bacteriology, specific: phthisiology and venereology. Epidemiology was one direction of infectology and was associated with it in the classical form,

dealing with issues of the area of ​​the epidemic process - the issues of the spread of infectious pathogens. Microbiology deals with the study of the pathogenic properties of living organisms. Hygiene, antiseptics, asepsis and vaccination deal with issues of prevention and containment of the spread of infectious diseases and the formation of pandemics in endemic, and more often, in the era of globalization, climate collapse and global warming - in non-endemic regions.

Types of infections

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

Generalized infection- an infection in which pathogens spread mainly by lympho-hematogenous route throughout the macroorganism.

local infection- local damage to the tissues of the body under the influence of pathogenic factors of the infectogen 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. In some cases, a local infection, from an infectious disease specialist, can go into surgical practice or into the lot of specialists, depending on the affected organs, and on the degree of chronicity of the process (otolaryngologist - tonsillitis, urologist - prostatitis, osteomyelitis, periodontitis - maxillofacial surgeon, lung abscess, lung gangrene - thoracic surgeon, rheumatoid arthritis - rheumatologist, meningoencephalitis, gangliitis, arachnoiditis - neurologist, vasculitis - vascular surgeon; nephritis, cystitis, pyelonephritis - nephrologist, pneumonia, bronchitis, pleurisy - pulmonologist, gastroenteritis, hepatitis - gastroenterologist, peritonitis - abdominal surgeon , appendicitis, colitis - colorectal surgeon)

General infection- the penetration of microorganisms into the blood and their distribution 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.).

Intercurrent infection- an infection that occurs secondary to an existing one, or to an existing disease, for example, with diabetes mellitus, or with renal and hepatic insufficiency. It is one type of immunodeficiency.

Manifest infection - an infection with obvious specific clinical signs.

Focal infection

An infection that occurs as a result of inflammation of an organ, accompanied by tissue destruction.

Stages of infectious diseases

Incubation period- [from lat. incubatio"hatching chicks"]. Usually, between the penetration of an infectious agent into the body and the manifestation of clinical signs, there is a certain period of time for each disease - an incubation period that is characteristic only for exogenous infections. During this period, the pathogen multiplies, the accumulation of both the pathogen and the toxins released by it occurs up to a certain threshold value, for which the body begins to respond with clinically pronounced reactions. The duration of the incubation period can vary from several hours and days to several years.

prodromal period- [from other Greek. πρόδρομος "running ahead, preceding"]. As a rule, the initial clinical manifestations do not carry any pathognomonic [from other Greek. πάθος "disease" + γνώμων "interpreter, caretaker, norm, rule"] for a specific sign infection. Weakness, headache, feeling of weakness are common. This stage of an infectious disease is called the prodromal period, or "harbinger stage." Its duration does not exceed 24-48 hours.

The period of development of the disease- during this phase, personality traits of the disease or signs common to many infectious processes (fever, inflammatory changes, etc.) appear. In the clinically pronounced phase, the stages of increasing symptoms (stadium incrementum), flowering of the disease (stadium acme) and extinction of manifestations (stadium decrementum) can be distinguished.

convalescence- [from lat. re-, repetition of action, + convalescentia, convalescence]. The period of recovery, or convalescence, as the final period of an infectious disease, can be fast (crisis) or slow (lysis), and also be characterized by a transition to a chronic state. In favorable cases, clinical manifestations usually disappear faster than the normalization of morphological disorders of organs and tissues and the complete removal of the pathogen from the body. Recovery may be complete or be accompanied by the development of complications (for example, from the side of the central nervous system, musculoskeletal system, or cardiovascular system). The period of final removal of the infectious agent can be delayed and for some infections (eg, typhus) can be decades.

Literature

• Gertsenstein G. M., Sokolov A. m.,. Infectious diseases // Encyclopedic Dictionary of Brockhaus and Efron: in 86 volumes (82 volumes and 4 additional). - St. Petersburg, 1890-1907.
• Borinskaya S. A. Infections as a selection factor // anthropogenez.ru.

31) Characteristic features of infectious diseases.

PECULIARITIES:

1) Specificity - each pathogen causes an infectious disease specific to it, with a specific localization in the organ / tissue.

2) Contagiousness - The ability to be transmitted from an infected to an uninfected, i.e. spread rapidly in susceptible populations.

3) The cyclicity of the flow, i.e. periods available:

1. Incubation period- the time that elapses from the moment of infection to the onset of clinical manifestations of the disease. Depending on the properties of the pathogen, the immune status of the macroorganism, the nature of the relationship between the macro- and microorganism, the incubation period can vary from several hours to several months and even years;

2. Prodromal period- the time of appearance of the first clinical symptoms of a general nature, non-specific for this disease, for example, weakness, fatigue, lack of appetite, etc.;

3. The period of acute manifestations of the disease- the height of the disease. At this time, symptoms typical of this disease appear: temperature curve, rashes, local lesions, etc.;

4. convalescence period- the period of fading and disappearance of typical symptoms and clinical recovery.

32 Types of infections -

1) Monoinfection - diseases caused by one type of microorganism.

2) Mixed infections - mixed - develop during infection with several types of microorganisms. Features: more severe course, pathogenicity does not have a total character. Pr - Syphilis + gonorrhea + chlamydia during sexual infection

Types of mixed: A) If microorganisms activate or aggravate the course of the disease - Activators or Synergists (Influenza virus and group B streptococci)

B) If microorganisms suppress each other - Antagonists (E. coli inhibits the activity of Salmonella, Shigella, Strepto / Staphylococcus).

C) They do not interact at all - they are indifferent.

3) Superinfections - secondary infections that have developed against the background of existing diseases. Re-infection occurs before recovery. (Syphilis).

4) Reinfection - re-infection with the same species after recovery. Gonorrhea, syphilis, meningococcal infections, scarlet fever, dysentery, erysipelas.

5) Relapse - infection during the action of a pathogen already present in the body, exacerbation of clinical symptoms.

6) The occurrence of an infectious process caused by the activation of the normal flora that inhabits the skin and mucous membranes is referred to as autoinfection.

7) Secondary infection - occurs against the background of a developed primary disease and is caused by another type of pathogen .. It happens Exogenous / Endogenous. A) exogenous: when the pathogen enters the body from outside.

B) Endogenous(oppurtonic) - Caused by representatives of the normal microflora with a decrease in the body's defenses. (Esherichiosis, the introduction of intestinal bacteria into the urinary tract.). An important feature is the absence of an incubation period. A variety of endogenous infections - autoinfections, they arise as a result of self-infection by transferring the pathogen from one biotope to another.

33 .Ways of entry of microbes into the human body.

Transmission route - a set of transmission factors () that ensure the transfer of a pathogenic agent from a patient or carrier to a healthy one.

The mechanism of transmission is the method of movement of the pathogen from the source into the body. Has 3 stages:

1) Removal of the pathogen from the source into the environment.

2) The stay of the pathogen in the environment and its objects (In transmission factors).

3) Penetration of the pathogen into the body.

Depending on the mechanism, there are ways:

1) The fecal-oral mechanism has an alimentary (through food), water, contact-household transmission routes.

2) Blood (transmissible) - parenteral, sexual, through insect bites.

3) Aerogenic - airborne, airborne.

4) Contact - wound and contact-sexual.

For many pathogens, the transmission route is strictly specific, and if it is violated (when Shigella enters the respiratory tract), it can be interrupted and the disease does not occur, or the disease can be aggravated even more (treponema pallidum enters the bloodstream).

The spread of bacteria, viruses and toxins in the patient's body.

Any infectious disease, regardless of the clinical signs and localization of the microbe in the body, is a disease of the whole organism. If pathogenic microbes have entered the blood vessels and begin to multiply in the blood, then they very quickly penetrate into all internal organs and tissues. This form of infection is called septicemia. It is characterized by the rapidity and malignancy of the course and often ends in death. When microbes are temporarily in the blood and do not multiply in it, but through it they are only transferred to other sensitive tissues and organs, where they then multiply, the infection is usually called bacteremia. Sometimes microbes, having penetrated into the body, remain only in the damaged tissue and, multiplying, release toxins. The latter, penetrating into the blood, cause general severe poisoning (tetanus, malignant edema). This process is called toxemia. The ways of excreting pathogenic microbes from the body are also different: with saliva, sputum, urine, feces, milk, secretions from the birth canal.

Nosocomial infections

Nosocomial infections(Also hospital, nosocomial) - according to the WHO definition, any clinically expressed diseases of microbial origin that affect the patient as a result of his hospitalization or visit to a medical institution for the purpose of treatment, or within 30 days after discharge from the hospital (for example, wound infection), as well as hospital personnel by virtue of the implementation their activities, regardless of whether the symptoms of this disease appear or do not appear during the stay of these persons in the hospital.

An infection is considered nosocomial if it first manifests itself 48 hours or more after being in the hospital, provided there are no clinical manifestations of these infections at the time of admission and the likelihood of an incubation period is excluded. In English, such infections are called nosocomial infections, from other Greek. νοσοκομείον - hospital (from νόσος - illness, κομέω - I care).

Hospital infections should be distinguished from the often confused related concepts of iatrogenic and opportunistic infections.

Iatrogenic infections- infections caused by diagnostic or therapeutic procedures.

Opportunistic infections- infections that develop in patients with damaged immune defense mechanisms.

Story

From the time of the establishment of the first maternity hospital in the 17th century until the middle of the 19th century, puerperal fever raged in European maternity hospitals, during epidemics of which mortality took up to 27% of women in childbirth to the grave. It was possible to cope with puerperal fever only after its infectious etiology was established and aseptic and antiseptic methods were introduced in obstetrics.

Examples of nosocomial infections

• Ventilator-associated pneumonia (VAP)
• Tuberculosis
• Urinary tract infections
• hospital pneumonia
• Gastroenteritis
• Staphylococcus aureus
• Methicillin-resistant Staphylococcus aureus(MRSA)
• Pseudomonas aeruginosa
• Acinetobacter baumannii
• Stenotrophomonas maltophilia
• Vancomycin-resistant enterococci
• Clostridium difficile

Epidemiology

In the United States, the Centers for Disease Control and Prevention estimates that about 1.7 million cases of nosocomial infections caused by all types of microorganisms cause or accompany 99,000 deaths each year.

In Europe, according to the results of hospital studies, the death rate from nosocomial infections is 25,000 cases per year, of which two-thirds are caused by gram-negative microorganisms.

In Russia, about 30 thousand cases are officially recorded annually, which indicates the shortcomings of the statistics. A study conducted in 32 emergency hospitals in the country showed that hospital infections develop in 7.6 percent of patients treated in a hospital. If we take into account that the approximate number of patients treated in hospitals in Russia is 31-32 million patients, then we should have 2 million 300 thousand cases of hospital infections per year.

Nosocomial agents can cause severe pneumonia, infections of the urinary tract, blood and other organs.

Nosocomial infections are characterized by their own epidemiology features that distinguish it from classical infections. These include: the originality of the mechanisms and factors of transmission, the peculiarities of the course of epidemiological and infectious processes, the important role of the medical staff of health facilities in the occurrence, maintenance and spread of foci of nosocomial infections.

Many types of infections are difficult to treat due to antibiotic resistance, which is gradually spreading among gram-negative bacteria that are dangerous to people in the community environment.

For HAI to occur, the following must be present: links infectious process:

• source of infection (host, patient, healthcare worker);
• pathogen (microorganism);
• transmission factors
• susceptible organism

Sources in most cases serve:

• medical personnel;
• carriers of latent forms of infection;
• patients with acute, erased or chronic form of infectious diseases, including wound infection;

Visitors to hospitals are very rarely sources of nosocomial infections.

Transfer factors most often dust, water, food, equipment and medical instruments act.

Leading ways of infection in the conditions of LPO are contact-household, air-drop and air-dust. The parenteral route is also possible (typical for hepatitis B, C, D, etc.)

Mechanisms of transmission : aerosol, fecal-oral, contact, blood contact.

Contributing factors

Factors in the nosocomial environment that contribute to the spread of nosocomial infections include:

• underestimation of the epidemic danger of nosocomial sources of infection and the risk of infection through contact with the patient;
• LPO overload;
• the presence of unidentified carriers of nosocomial strains among medical staff and patients;
• violation by medical staff of the rules of asepsis and antisepsis, personal hygiene;
• untimely carrying out of the current and final disinfection, violation of the cleaning regime;
• insufficient equipment of health care facilities with disinfectants;
• violation of the regime of disinfection and sterilization of medical instruments, devices, devices, etc.;
• outdated equipment;
• unsatisfactory condition of catering facilities, water supply;
• lack of filtration ventilation.

Risk group

Individuals at increased risk of HAI infection:

1. Sick:
   • homeless, migrant population,
   • with long-term untreated chronic somatic and infectious diseases,
   • unable to receive special medical care;
2. Persons who:
   • prescribed therapy that suppresses the immune system (irradiation, immunosuppressants);
   • extensive surgical interventions are carried out followed by blood replacement therapy, program hemodialysis, infusion therapy;
3. Women in labor and newborns, especially premature and postmature;
4. Children with congenital developmental anomalies, birth trauma;
5. LPO medical staff.

Etiology

In total, there are more than 200 agents that can cause nosocomial infections. Before the advent of antibiotics, the main ones were streptococci and anaerobic bacilli. However, after the start of the clinical use of antibiotics, previously non-pathogenic (or opportunistic) microorganisms became the causative agents of the main nosocomial infections: St. aureus, St. epidermidis, St. saprophiticus, Escherichia coli, Enterococcus faecalis, Enterococcus durans, Klebsiella sp., Proteus mirabilis, Providencia spp, Acinetobacter, Citrobacter, Serratia marcescens.

It has also been established that nosocomial infection may be associated with the spread of rotavirus, cytomegalovirus infection, campylobacter, hepatitis B, C and D viruses, as well as HIV infection.

As a result of the circulation of microorganisms in the department, their natural selection and mutation occur with the formation of the most resistant hospital strain, which is the direct cause of nosocomial infections.

hospital strain - this is a microorganism that has changed as a result of circulation in the department in terms of its genetic properties, as a result of mutations or gene transfer (plasmids) has acquired some characteristic features unusual for the "wild" strain, allowing it to survive in a hospital.

The main features of the adaptation are resistance to one or more broad-spectrum antibiotics, resistance to environmental conditions, and a decrease in sensitivity to antiseptics. Hospital strains are very diverse, each hospital or department may have its own characteristic strain with a set of biological properties peculiar only to it.

Classification

1. Depending on the ways and factors of transmission, nosocomial infections are classified:
   • Airborne (aerosol)
   • Introductory-alimentary
   • Contact household
   • Contact instrumental
   • Post-injection
   • Postoperative
   • Postpartum
   • Posttransfusion
   • Postendoscopic
   • Post-transplant
   • Post-dialysis
   • Posthemosorption
   • Post-traumatic infections
   • Other forms.
2. From the nature and duration of the flow:
   • Acute
   • Subacute
   • Chronic.
3. By severity:
   • heavy
   • Medium-heavy
   • Mild forms of clinical course.
4. Depending on the degree of spread of infection:
   • Generalized infections: bacteremia (viremia, mycemia), septicemia, septicopyemia, toxic-septic infection (bacterial shock, etc.).
   • Localized infections
   • Infections of the skin and subcutaneous tissue (burn, surgical, traumatic wounds, post-injection abscesses, omphalitis, erysipelas, pyoderma, abscess and phlegmon of the subcutaneous tissue, paraproctitis, mastitis, ringworm, etc.);
   • Respiratory infections (bronchitis, pneumonia, lung abscess and gangrene, pleurisy, empyema, etc.);
   • Eye infections (conjunctivitis, keratitis, blepharitis, etc.);
   • ENT infections (otitis media, sinusitis, rhinitis, mastoiditis, tonsillitis, laryngitis, pharyngitis, epiglottitis, etc.);
   • Dental infections (stomatitis, abscess, etc.);
   • Infections of the digestive system (gastroenterocolitis, enteritis, colitis, cholecystitis, hepatitis, peritonitis, peritoneal abscesses, etc.);
   • Urological infections (bacteriuria, pyelonephritis, cystitis, urethritis, etc.);
   • Infections of the reproductive system (salpingoophoritis, endometritis, etc.);
   • Infections of bones and joints (osteomyelitis, infection of the joint or joint bag, infection of the intervertebral discs);
   • CNS infections (meningitis, brain abscess, ventriculitis, etc.);
   • Infections of the cardiovascular system (infections of arteries and veins, endocarditis, myocarditis, pericarditis, postoperative mediastinitis).

Prevention

Prevention of nosocomial infections is a complex and complex process that should include three components:

• minimizing the possibility of introducing infection from outside;
• exclusion of the spread of infection between patients within the institution;
• exclusion of the removal of infection outside the hospital.

Treatment

Treatment of nosocomial infection

Ideally, a narrow-spectrum antimicrobial agent that targets the specific microorganism isolated from microbiological testing should be prescribed. However, in practice, nosocomial infection, especially in the early days, is almost always treated empirically. The choice of the optimal scheme of antimicrobial therapy depends on the prevailing microflora in the department and the spectrum of its antibiotic resistance.

In order to reduce antibiotic resistance of pathogens, regular rotation of antibacterial drugs should be practiced (when certain antibiotics are used in the department for empirical therapy for several months, and then replaced by the next group).

Starting Antimicrobial Therapy

Nosocomial infection caused by gram-positive microorganisms is most effectively treated with vancomycin, while carbapenems (imipenem and meropenem), fourth-generation cephalosporins (cefepime, cefpirome) and modern aminoglycosides (amikacin) have the highest activity against gram-negative bacteria.

From the foregoing, one should not conclude that nosocomial infection is amenable only to the above means. For example, pathogens of urinary tract infections remain highly sensitive to fluoroquinolones, third-generation cephalosporins, etc.

But a serious nosocomial infection really requires the appointment of carbapenems or IV generation cephalosporins, since they have the widest spectrum of activity and act on the polymicrobial flora, including multidrug-resistant gram-negative pathogens and many gram-positive microorganisms. The disadvantage of drugs of both groups is the lack of activity against methicillin-resistant staphylococci, so in severe cases they have to be combined with vancomycin.

In addition, all of these agents do not act on fungal pathogens, whose role in the development of nosocomial infections has increased significantly. Accordingly, in the presence of risk factors (for example, severe immunodeficiency), antifungal agents (fluconazole, etc.)

Localization

Drugs of choice

In the 90s of the twentieth century, it was shown that the effectiveness of starting antibiotic therapy has a direct impact on the mortality of hospitalized patients. Mortality among patients who received ineffective initial therapy was higher than in patients who were prescribed antibiotics that are active against most pathogens. Moreover, in the case of inadequate initial therapy, even a subsequent change in the antibiotic, taking into account microbiological data, did not lead to a decrease in mortality.

Thus, in severe nosocomial infections, the very concept of “reserve antibiotic” loses its meaning. The effectiveness of initial therapy is an important factor on which the prognosis for life depends.

Based on these data, a de-escalation therapy concept. Its essence lies in the fact that as a starting empiric therapy, which is started immediately after the diagnosis is established, a combination of antimicrobial agents acting on all possible infectious agents is used. For example, carbapenem or cefepime is combined with vancomycin (plus fluconazole) depending on the composition of the likely pathogens.

The arguments in favor of combination therapy are:

• a wider range of activities;
• overcoming resistance, the likelihood of which is higher with the use of one drug;
• availability of theoretical data on the synergy of certain means.

Prior to the use of antibiotics, it is necessary to take samples of biological fluids for microbiological examination. After receiving the results of a microbiological study and a clinical assessment of the effectiveness of treatment, after 48-72 hours, correction of therapy is possible, for example, the abolition of vancomycin if a gram-negative pathogen is detected. Theoretically, it is possible to change the entire combination to a drug with a narrower spectrum of action, although in a seriously ill patient who has responded to therapy, any doctor will prefer to keep the prescribed antibiotics.

The possibility of introducing de-escalation therapy depends on the effective work of the microbiological service and the degree of confidence in its results. If the causative agent remains unknown, then this concept loses its meaning and may lead to poor treatment outcomes. De-escalation therapy should be considered first in patients with serious life-threatening infections (eg, ventilator-associated pneumonia, sepsis).

It should be borne in mind that the reverse approach (that is, escalation of therapy) in such situations may result in the death of the patient even before receiving the result of a microbiological study.

3. Meningococcal infection (definition). Etiology, epidemiology, clinical variants.

Meningococcal infection (MI) (Meningitiscerebrospinalisepidemica) - the island is an infectious disease caused by meningococcus, transmitted by airborne droplets and occurring in various clinical variants (nasopharyngitis, meningitis, meningococcemia, etc.).

Etiology. The causative agent of the disease Neisseriameningitidis(Vekselbaum meningococcus). Gram-negative diplococcus, immobile, has no flagella and capsules, does not form spores. Cultivated on media with human or animal protein, aerobic. Several serotypes (A, B, C, D, X, Y, Z, etc.). Currently, serotypes B and C are more common. The pathogen produces enzymes - hyaluronidase and neuraminidase. The main factor of pathogenicity is endotoxin (protein-lipopolysaccharide complex).

Unstable in the environment, quickly dies outside the body (under the influence of direct sunlight, heat, disinfectant solutions, in 70% alcohol). At a temperature of +50 ° C, meningococcus dies after 5 minutes, at low temperatures (-7 ... -10 ° C) - after 2 hours.

Epidemiology. Source of infection: patients and carriers of meningococcus. Patients with localized forms of MI present the greatest danger. There are up to 2,000 carriers of meningococcus per patient with a manifest form of MI.

Transfer mechanisms: drip, less often - contact. Basic transmission path - airborne. The causative agent is released from the upper respiratory tract when sneezing, coughing, crying.

Susceptibility to MI universal. Contagiousness index - 10-15%.

Seasonality. An increase in the incidence in the winter-spring period is characteristic.

Immunity is type specific.

Mortality with generalized forms, it ranges from 5-6% to 12-14%, and in young children - up to 50%.

Classification of meningococcal infection.

I. Localized forms:

Meningococcal nasopharyngitis;

Carriage of meningococcus.

II. Generalized forms:

Meningococcemia (mild, moderate, severe, hypertoxic);

Purulent meningitis;

Purulent meningoencephalitis;

Combined form (meningitis with meningococcemia, etc.).

III. Rare forms:

Myocarditis;

Osteomyelitis;

Iridocyclitis, etc.

By gravity:

1.Light form.

2. Moderate form.

3. Heavy form.

4. Hypertoxic (lightning) form.

Severity Criteria:

The severity of the syndrome of intoxication;

Expression of local changes.

Downstream (by nature):

1.Smooth.

2.Unsmooth:

With complications;

With layering of secondary infection;

With exacerbation of chronic diseases.

Clinical picture. Incubation period - from 1-2 to 10 days.

Localized Forms. Meningococcal nasopharyngitis (up to 80%). Begins acutely, moderately severe fever, malaise, headache. Nasal breathing is difficult, scanty discharge from the nose, sore throat. Diffuse hyperemia of the mucous membranes and granularity of the posterior pharyngeal wall. There are no disturbances from the internal organs. Symptoms of the disease disappear after 7-10 days.

Carriage of meningococcus- inoculation of meningococcus from nasopharyngeal mucus in the absence of signs of inflammation and increase in titers of specific antibodies in the dynamics of the study.

Generalized forms. Meningococcemia(4-10%). The syndrome of intoxication and skin lesions are pronounced, other organs (joints, kidneys, adrenal glands, spleen) may be involved. It starts suddenly, with a rise in t of the body (up to 39-40 ° C and above). Headache, malaise, lethargy, refusal to eat, vomiting is possible. The main symptom of meningococcemia is a rash. At the beginning, roseolous or roseolopapular elements, of various diameters, disappearing with pressure,

located throughout the body (without a specific localization). After a few hours, hemorrhagic elements appear: purple-red with a bluish tint, which do not disappear when pressed, of various diameters (from petechiae to ecchymosis), rising above the skin surface, dense on palpation, in typical cases - irregular, "star" shape. Elements fade in 1-2 days. In the center of large lesions appear necrosis > ulcers, the formation of rough scars (see Fig. 14). In especially severe cases, the development of dry gangrene of the fingers and toes, auricles, and nose is possible. The appearance of a rash in the early stages of the disease on the face, eyelids, upper body is a prognostically unfavorable sign.

meningococcal meningitis. It begins acutely with a rise in body temperature to 40 ° C and above, chills, severe headache. The headache is aggravated by sound and light stimuli, turning the head, and the phenomena of hyperesthesia are pronounced. Repeated vomiting that is not associated with eating and does not bring relief. meningeal symptoms. The face is pale, the sclera are injected. Heart sounds are muffled, breathing is frequent, superficial. The cerebrospinal fluid is turbid, milky-white in color, flows out under pressure; neutrophilic pleocytosis, a slight increase in protein content.

Meningococcal meningoencephalitis. Mostly in young children. Acute onset, t the body is febrile. Encephalic syndrome - motor excitation, convulsions, loss of consciousness, damage to the cranial nerves, hemiparesis. Meningeal symptoms are mild. Often fatal.

combined form(meningococcal meningitis in combination with meningococcemia). See manifestations above.

rare forms MI (arthritis, myocarditis, osteomyelitis, iridocyclitis And. others) have no specific clinical symptoms.

Complications. specific complications, life-threatening patients - infectious-toxic shock, acute above renal failure, edema-swelling of the brain, DIC.

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, 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 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 infectious dose of pathogens also significantly influences the formation of the infectious process and the severity of the clinical manifestations of an infectious disease.

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 2nd-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 the body, 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 many months or even many years, a 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 various causes - 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.

Historically, the word "infection ” (lat. inficio - infect) was first introduced to refer to sexually transmitted diseases.

Infection- the totality of all biological phenomena and processes that occur in the body during the introduction and reproduction of microorganisms in it, the result of the relationship between the macro- and microorganism in the form of adaptive and pathological processes in the body, i.e. infectious process.

infectious disease- the most pronounced form of the infectious process.

The term infection or a synonym for an infectious process means a set of physiological and pathological regenerative-adaptive reactions that occur in a susceptible macroorganism under certain environmental conditions as a result of its interaction with pathogenic or opportunistic bacteria, fungi and viruses that have penetrated and multiply in it and are aimed at maintaining the constancy of the internal macroorganism environment (homeostasis). A similar process, but caused by protozoa, helminths and insects - representatives of the kingdom Animalia, is called invasion.

The occurrence, course and outcome of the infectious process are determined by three groups of factors: 1) quantitative and qualitative characteristics of the microbe - the causative agent of the infectious process; 2) the state of the macroorganism, the degree of its susceptibility to the microbe; 3) the action of physical, chemical and biological factors of the environment surrounding the microbe and macroorganism, which determines the possibility of establishing contacts between representatives of different species, the common habitat of different species, food ties, the density and number of populations, the features of the transfer of genetic information, the features of migration, etc. e. At the same time, in relation to a person, under the conditions of the external environment, first of all, one should understand social conditions his life activity. The first two biological factors are direct participants in the infectious process that develops in a macroorganism under the action of a microbe. At the same time, the microbe determines the specificity of the infectious process, and the decisive integral contribution to the form of manifestation of the infectious process, its duration, severity of manifestations and outcome is made by the state of the macroorganism, primarily the factors of its nonspecific resistance, which come to the aid of factors of specific acquired immunity. The third, environmental, factor has an indirect effect on the infectious process, reducing or increasing the susceptibility of the macroorganism, or reducing and increasing the infectious dose and virulence of the pathogen, activating the mechanisms of infection and the corresponding routes of infection transmission, etc.

Mutualism- mutually beneficial relationship (for example, normal microflora).

Commensalism- one partner (microbe) benefits without causing much harm to the other. It should be noted that with any type of relationship, a microorganism can manifest its pathogenic properties (for example, conditionally pathogenic microbes-commensals in an immunodeficient host).

pathogenicity(“disease-producing”) is the ability of a microorganism to cause a disease. This property characterizes species genetic features of microorganisms, their genetically determined characteristics, allowing to overcome the host's defense mechanisms, to manifest their pathogenic properties.

Virulence - phenotypic(individual) quantitative expression of pathogenicity (pathogenic genotype). Virulence can vary and can be determined by laboratory methods (more often DL50 - 50% lethal dose - the number of pathogenic microorganisms that can cause the death of 50% of infected animals).

According to their ability to cause diseases, microorganisms can be divided into pathogenic, conditionally pathogenic, non-pathogenic. Conditionally pathogenic microorganisms are found both in the environment and in the composition of normal microflora. Under certain conditions (immunodeficiency states, injuries and operations with the penetration of microorganisms into tissues), they can cause endogenous infections.

3) Factors of pathogenicity of microorganisms: adhesins. Factors of invasion and aggression. Tropism of microbes. Relationship between microbial cell structure and pathogenicity factors.

The main factors of pathogenicity of microorganisms- adhesins, pathogenicity enzymes, substances that inhibit phagocytosis, microbial toxins, under certain conditions - capsule, microbial motility. Virulence is associated with toxigenicity(ability to produce toxins) and invasiveness(the ability to penetrate into the tissues of the host, multiply and spread). Toxigenicity and invasiveness have independent genetic control and are often inversely related (a pathogen with high toxigenicity may have low invasiveness and vice versa).

Adhesins and colonization factors more often surface structures of a bacterial cell, with the help of which bacteria recognize receptors on cell membranes, attach to them and colonize tissues. The function of adhesion is performed pili, outer membrane proteins, LPS, teichoic acids, viral hemagglutinins. Adhesion is a trigger mechanism for the implementation of pathogenic properties of pathogens.

Factors of invasion, penetration into cells and tissues of the host. Microorganisms can multiply outside cells, on cell membranes, inside cells. Bacteria secrete substances that help to overcome the host's barriers, their penetration and reproduction. In Gram-negative bacteria, these are usually outer membrane proteins. These factors include pathogenicity enzymes.

Enzymes of pathogenicity are factors of aggression and protection of microorganisms. The ability to form exoenzymes largely determines the invasiveness of bacteria - the ability to penetrate mucous, connective tissue and other barriers. These include various lytic enzymes - hyaluronidase, collagenase, lecithinase, neuraminidase, coagulase, proteases. Their characteristics are given in more detail in the lecture on the physiology of microorganisms.

4) Bacterial toxins: exotoxins and endotoxins, nature and properties, mechanisms of action.

The most important factors of pathogenicity are considered toxins which can be divided into two large groups - exotoxins and endotoxins.

Exotoxins are produced into the external environment (host organism), usually of a protein nature, can exhibit enzymatic activity, can be secreted by both gram-positive and gram-negative bacteria. They are highly toxic, thermally unstable, and often exhibit antimetabolite properties. Exotoxins show high immunogenicity and cause the formation of specific neutralizing antibodies - antitoxins. According to the mechanism of action and the point of application, exotoxins differ - cytotoxins (enterotoxins and dermatonecrotoxins), membrane toxins (hemolysins, leukocidins), functional blockers (cholerogen), exfoliants and erythrogenins. Microbes capable of producing exotoxins are called toxigenic.

Endotoxins are released only when bacteria die, are characteristic of gram-negative bacteria, are complex chemical compounds of the cell wall (LPS) - see the lecture on the chemical composition of bacteria for more details. Toxicity is determined by lipid A, the toxin is relatively heat resistant; immunogenic and toxic properties are less pronounced than those of exotoxins.

The presence of capsules in bacteria complicates the initial stages of protective reactions - recognition and absorption (phagocytosis). An essential factor of invasiveness is the mobility of bacteria, which determines the penetration of microbes into cells and into intercellular spaces.

Pathogenicity factors are controlled by:

chromosome genes;

Plasmid genes;

Genes introduced by temperate phages.

Infection(infectio - infection) - the process of penetration of a microorganism into a macroorganism and its reproduction in it.

infectious process- the process of interaction between a microorganism and the human body.

The infectious process has various manifestations: from asymptomatic carriage to an infectious disease (with recovery or death).

infectious disease is an extreme form of infection.

An infectious disease is characterized by:

1) Availability certain live pathogen ;

2) infectiousness , i.e. pathogens can be transmitted from a sick person to a healthy one, which leads to a wide spread of the disease;

3) the presence of a certain incubation period And characteristic succession periods during the course of the disease (incubation, prodromal, manifest (height of the disease), recovalescence (recovery));

4) development clinical symptoms characteristic of the disease ;

5) availability immune response (more or less prolonged immunity after the transfer of the disease, the development of allergic reactions in the presence of a pathogen in the body, etc.)

The names of infectious diseases are formed from the name of the pathogen (species, genus, family) with the addition of the suffixes "oz" or "az" (salmonellosis, rickettsiosis, amoebiasis, etc.).

Development infectious process depends:

1) from the properties of the pathogen ;

2) from the state of the macroorganism ;

3) from environmental conditions , which can affect both the state of the pathogen and the state of the macroorganism.

properties of pathogens.

The causative agents are viruses, bacteria, fungi, protozoa, helminths (their penetration is an invasion).

Microorganisms that can cause infectious diseases are called pathogenic , i.e. disease-causing (pathos - suffering, genos - birth).

There are also conditionally pathogenic microorganisms that cause diseases with a sharp decrease in local and general immunity.

The causative agents of infectious diseases have properties pathogenicity And virulence .

pathogenicity and virulence.

pathogenicity- this is the ability of microorganisms to penetrate into a macroorganism (infectivity), take root in the body, multiply and cause a complex of pathological changes (disorders) in organisms sensitive to them (pathogenicity - the ability to cause an infectious process). Pathogenicity is a specific, genetically determined trait or genotypic trait.

The degree of pathogenicity is determined by the concept virulence. Virulence is a quantitative expression or pathogenicity. Virulence is phenotypic trait. This is a property of the strain, which manifests itself under certain conditions (with the variability of microorganisms, changes in the susceptibility of the macroorganism).

Quantitative indicators of virulence :

1) DLM(Dosis letalis minima) - minimum lethal dose- the minimum number of microbial cells that causes the death of 95% of susceptible animals under given specific experimental conditions (type of animal, weight, age, method of infection, time of death).

2) LD 50 - the amount that causes the death of 50% of experimental animals.

Since virulence is a phenotypic trait, it changes under the influence of natural causes. It can also artificially change (raise or lower). Raise carried out by repeated passage through the body of susceptible animals. downgrade - as a result of exposure to adverse factors: a) high temperature; b) antimicrobial and disinfectant substances; c) growing on unfavorable nutrient media; d) the body's defenses - passage through the body of little susceptible or non-receptive animals. Microorganisms with weakened virulence used to get live vaccines.

Pathogenic microorganisms also specificity, organotropism and toxicity.

Specificity- ability to call certain infectious disease. Vibrio cholerae causes cholera, Mycobacterium tuberculosis - tuberculosis, etc.

Organotropism- the ability to infect certain organs or tissues (the causative agent of dysentery - the mucous membrane of the large intestine, the influenza virus - the mucous membrane of the upper respiratory tract, the rabies virus - the nerve cells of the ammon's horn). There are microorganisms that can infect any tissue, any organ (staphylococci).

Toxicity- the ability to form toxic substances. Toxic and virulent properties are closely related.

virulence factors.

Traits that determine pathogenicity and virulence are called virulence factors. These include certain morphological(the presence of certain structures - capsules, cell wall), physiological and biochemical signs(production of enzymes, metabolites, toxins that have an adverse effect on the macroorganism), etc. By the presence of virulence factors, pathogenic microorganisms can be distinguished from non-pathogenic ones.

Virulence factors include:

1) adhesins (provide adhesion) – specific chemical groups on the surface of microbes, which, like a "key to a lock", correspond to the receptors of sensitive cells and are responsible for the specific adhesion of the pathogen to the cells of the macroorganism;

2) capsule – protection against phagocytosis and antibodies; bacteria surrounded by a capsule are more resistant to the action of the protective forces of the macroorganism and cause a more severe course of infection (causative agents of anthrax, plague, pneumococci);

3) superficial substances of the capsule or cell wall of various nature (surface antigens): protein A of staphylococcus, protein M of streptococcus, Vi-antigen of typhoid bacilli, lipoproteins of gram "-" bacteria; they perform the functions of immune suppression and non-specific protective factors;

4) aggression enzymes: proteases destroying antibodies; coagulase, coagulating blood plasma; fibrinolysin, dissolving fibrin clots; lecithinase, destroying the lecithin of membranes; collagenase destroying collagen; hyaluronidase, destroying hyaluronic acid of the intercellular substance of the connective tissue; neuraminidase destroying neuraminic acid. Hyaluronidase breaking down hyaluronic acid increases permeability mucous membranes and connective tissue;

toxins - microbial poisons - powerful aggressors.

Virulence factors provide:

1) adhesion - attachment or adherence of microbial cells to the surface of sensitive cells of the macroorganism (to the surface of the epithelium);

2) colonization – reproduction on the surface of sensitive cells;

3) penetration - the ability of some pathogens to penetrate (penetrate) into cells - epithelial, leukocytes, lymphocytes (all viruses, some types of bacteria: shigella, escherichia); cells die at the same time, and the integrity of the epithelial cover may be violated;

4) invasion - the ability to penetrate through the mucous and connective tissue barriers into the underlying tissues (due to the production of hyaluronidase and neuraminidase enzymes);

5) aggression - the ability of pathogens to suppress the nonspecific and immune defenses of the host organism and cause the development of damage.

Toxins.

Toxins are poisons of microbial, plant or animal origin. They have a high molecular weight and cause the formation of antibodies.

Toxins are divided into 2 groups: endotoxins and exotoxins.

Exotoxinsstand out into the environment during the life of a microorganism. Endotoxins tightly bound to the bacterial cell stand out into the environment after cell death.

Properties of endo and exotoxins.

Exotoxins form causative agents of the so-called toxinemia infections, which include difteria, tetanus, gas gangrene, botulism, some forms of staphylococcal and streptococcal infections.

Some bacteria simultaneously form both exo- and endotoxins (E. coli, Vibrio cholerae).

Getting exotoxins.

1) growing a toxigenic (forming exotoxin) culture in a liquid nutrient medium;

2) filtration through bacterial filters (separation of exotoxin from bacterial cells); other cleaning methods can be used.

Exotoxins are then used to produce toxoids.

Obtaining toxoids.

1) 0.4% formalin is added to the exotoxin solution (the filtrate of the broth culture of toxigenic bacteria) and kept in a thermostat at 39-40C for 3-4 weeks; there is a loss of toxicity, but antigenic and immunogenic properties are preserved;

2) add preservative and adjuvant.

Anatoxins are molecular vaccines. They are used for specific prophylaxis of toxinemic infections , and to obtain therapeutic and prophylactic antitoxic sera, also used in toxin infections.

Getting endotoxins.

Various methods are used microbial cell destruction , and then cleaning is carried out, i.e. separation of endotoxin from other components of the cell.

Since endotoxins are lipopolysaccharides, they can be extracted from the microbial cell by breaking it down with TCA (trichloroacetic acid) followed by dialysis to remove proteins.

The environment is filled with a huge number of "inhabitants", among which there are various microorganisms: viruses, bacteria, fungi, protozoa. They can live in absolute harmony with a person (non-pathogenic), exist in the body without causing harm under normal conditions, but become more active under the influence of certain factors (conditionally pathogenic) and be dangerous to humans, causing the development of a disease (pathogenic). All these concepts relate to the development of the infectious process. What is an infection, what are its types and features - discussed in the article.

Basic concepts

An infection is a complex of relationships between various organisms, which has a wide range of manifestations - from asymptomatic carriage to the development of the disease. The process appears as a result of the introduction of a microorganism (virus, fungus, bacterium) into a living macroorganism, in response to which a specific protective reaction occurs on the part of the host.

Features of the infectious process:

1. Contagiousness - the ability to quickly spread from a sick person to a healthy one.
2. Specificity - a certain microorganism causes a specific disease, which has its characteristic manifestations and localization in cells or tissues.
3. Periodicity - each infectious process has periods of its course.

Periods

The concept of infection is also based on the cyclic nature of the pathological process. The presence of periods in development is characteristic of each similar manifestation:

1. The incubation period is the time that passes from the moment the microorganism enters the body of a living being until the first clinical signs of the disease appear. This period can last from a few hours to several years.
2. The prodromal period is the appearance of a general clinic characteristic of most pathological processes (headache, weakness, fatigue).
3. Acute manifestations - the peak of the disease. During this period, specific symptoms of infection develop in the form of rashes, characteristic temperature curves, tissue damage at the local level.
4. Reconvalescence is the time when the clinical picture fades and the patient recovers.

Types of infectious processes

To consider in more detail the question of what an infection is, you need to understand what it is. There are a significant number of classifications depending on the origin, course, localization, number of microbial strains, etc.

1. According to the method of penetration of pathogens:

• - characterized by the penetration of a pathogenic microorganism from the external environment;
• endogenous process - there is an activation of own conditionally pathogenic microflora under the influence of adverse factors.

2. By origin:

• spontaneous process - characterized by the absence of human intervention;
• experimental - the infection is bred artificially in the laboratory.

3. By the number of microorganisms:

• monoinfection - caused by one type of pathogen;
• mixed - several types of pathogens are involved.

4. By order:

• the primary process is a newly appeared disease;
• secondary process - accompanied by the addition of an additional infectious pathology against the background of a primary disease.

5. By localization:

• local form - the microorganism is located only in the place through which it entered the host organism;
• - pathogens spread throughout the body with further settling in certain favorite places.

6. Downstream:

• acute infection - has a vivid clinical picture and lasts no more than a few weeks;
• chronic infection - characterized by a sluggish course, can last for decades, has exacerbations (relapses).

7. By age:

• "Children's" infections - affect children mainly aged 2 to 10 years (chicken pox, diphtheria, scarlet fever, whooping cough);
• there is no concept of "adult infections" as such, since the children's body is also sensitive to those pathogens that cause the development of the disease in adults.

There are concepts of reinfection and superinfection. In the first case, a person who has fully recovered, after an illness, becomes infected again with the same pathogen. With superinfection, re-infection occurs even during the course of the disease (pathogen strains overlap each other).

Entry routes

There are the following ways of penetration of microorganisms, which ensure the transfer of pathogens from the external environment into the host organism:

• fecal-oral (consists of alimentary, water and contact household);
• transmissible (blood) - includes sexual, parenteral and through insect bites;
• aerogenic (air-dust and air-drop);
• contact-sexual, contact-wound.

Most pathogens are characterized by the presence of a specific route of penetration into the macroorganism. If the transmission mechanism is interrupted, the disease may not appear at all or worsen in its manifestations.

Localization of the infectious process

Depending on the affected area, the following types of infections are distinguished:

1. Intestinal. The pathological process occurs in the gastrointestinal tract, the pathogen penetrates the fecal-oral route. These include salmonellosis, dysentery, rotavirus, typhoid fever.
2. Respiratory. The process occurs in the upper and lower respiratory tract, microorganisms "move" in most cases through the air (influenza, adenovirus infection, parainfluenza).
3. Outdoor. Pathogens contaminate mucous membranes and skin, causing fungal infections, scabies, microsporia, STDs.
4. enters through the blood, spreading further throughout the body (HIV infection, hepatitis, diseases associated with insect bites).

Intestinal infections

Consider the features of pathological processes on the example of one of the groups - intestinal infections. What is an infection that affects the human gastrointestinal tract, and how is it different?

Diseases of the presented group can be caused by pathogens of bacterial, fungal and viral origin. Viral microorganisms that can penetrate into various parts of the intestinal tract are rotaviruses and enteroviruses. They are able to spread not only by the fecal-oral route, but also by airborne droplets, affecting the epithelium of the upper respiratory tract and causing herpes sore throat.

Bacterial diseases (salmonellosis, dysentery) are transmitted exclusively by the fecal-oral route. Infections of fungal origin occur in response to internal changes in the body that occur under the influence of prolonged use of antibacterial or hormonal drugs, with immunodeficiency.

Rotaviruses

Rotavirus intestinal infection, the treatment of which should be comprehensive and timely, in principle, like any other disease, accounts for half of the clinical cases of viral intestinal infectious pathologies. An infected person is considered dangerous to society from the end of the incubation period until full recovery.

Rotavirus intestinal is much more severe than in adults. The stage of acute manifestations is accompanied by the following clinical picture:

• abdominal pain;
• diarrhea (the stool is light in color, there may be blood impurities);
• bouts of vomiting;
• hyperthermia;
• runny nose;
• inflammatory processes in the throat.

Rotavirus in children in most cases is accompanied by outbreaks of the disease in school and preschool institutions. By the age of 5, most babies have experienced the effects of rotaviruses on themselves. The following infections are not as difficult as the first clinical case.

Surgical infection

Most patients requiring surgical intervention are interested in the question of what a surgical-type infection is. This is the same process of interaction of the human body with a pathogenic agent, which only occurs against the background of an operation or requires surgical intervention to restore functions in a certain disease.

Distinguish acute (purulent, putrefactive, specific, anaerobic) and chronic process (specific, nonspecific).

Depending on the localization of the surgical infection, diseases are distinguished:

• soft tissues;
• joints and bones;
• the brain and its structures;
• abdominal organs;
• organs of the chest cavity;
• pelvic organs;
• individual elements or organs (mammary gland, hand, foot, etc.).

Causative agents of surgical infection

Currently, the most frequent "guests" of acute purulent processes are:

• staphylococcus;
• Pseudomonas aeruginosa;
• enterococcus;
• coli;
• streptococcus;
• Proteus.

The entrance gates of their penetration are various damage to the mucous membranes and skin, abrasions, bites, scratches, gland ducts (sweat and sebaceous). If a person has chronic foci of accumulation of microorganisms (chronic tonsillitis, rhinitis, caries), then they cause the spread of pathogens throughout the body.

Infection treatment

At the heart of getting rid of the pathological microflora is aimed at eliminating the cause of the disease. Depending on the type of pathogen, the following groups of medicines are used:

1. Antibiotics (if the causative agent is a bacterium). The choice of a group of antibacterial agents and a specific drug is made on the basis of bacteriological examination and determination of the individual sensitivity of the microorganism.
2. Antiviral (if the pathogen is a virus). In parallel, drugs are used that strengthen the defenses of the human body.
3. Antimycotic agents (if the pathogen is a fungus).
4. Anthelmintic (if the pathogen is a helminth or the simplest).

Treatment of infections in children under 2 years of age is carried out in a hospital to avoid the development of possible complications.

Conclusion

After the onset of a disease that has a specific pathogen, the specialist differentiates and determines the need for hospitalization of the patient. Be sure to indicate the specific name of the disease in the diagnosis, and not just the word "infection". The case history, which is taken for inpatient treatment, contains all the data on the stages of diagnosis and treatment of a specific infectious process. If there is no need to hospitalize the patient, all such information is recorded in the outpatient card.