Pathogens of respiratory viral infections microbiology. Principles of rational therapy of acute respiratory viral infections in children. RNA may be

INFECTIONS (causative agents of influenza, ARVI, measles, rubella,

chickenpox, mumps).

Learning objective:

specific prevention of influenza, ARVI, measles, rubella,

rubella, chickenpox, mumps.

2. Specific prevention of influenza, ARVI, measles, rubella,

chickenpox, mumps.

2. Set up and take into account the results of RTGA for seroidentification for influenza.

3.Post and take into account the results of ELISA for serodiagnosis of ARVI.

PLAN:

1. 
   
2. 
   Principles of microbiological diagnosis of influenza, ARVI, measles, rubella, chickenpox, mumps.
3. 
   Preparations for etiotropic therapy and specific prevention of influenza, ARVI, measles, rubella, chickenpox, mumps.

INDEPENDENT WORK

1. Analysis of the supply and recording of the results of RIF for ARVI (demonstration).

2. Analysis of the supply and recording of the RTGA results for seroidentification when

influenza (demonstration).

3. Parsing the supply and recording the results of ELISA for serodiagnosis when

ARVI (demonstration).

Flu (from the French grippe) - acute infectious disease of the respiratory tract caused by the influenza virus. Included in the group of acute respiratory viral infections (ARVI). Periodically spreads in the form of epidemics and pandemics. Currently, more than 2000 variants of the influenza virus have been identified, differing in their antigenic spectrum.

The virus was first isolated in the 30s of the 20th century. Influenza viruses belong to the family Ortomyxoviridae, which includes the genera Influenza A, B, C. The antigenic properties of the internal proteins of the virion (M1 and NP) determine whether the influenza virus belongs to the genus A, B or C.

Viruses containing three HA subtypes (H1, H2, H3) and two NA subtypes (N1, N2) are of epidemic importance for humans. Influenza A and B viruses contain NA and NA as the main structural and antigenic components of the viral particle, which have hemagglutinating and neuraminidase activities. Influenza C virus does not have neuraminidase, but instead possesses a hemagglutinin esterase (entry) protein (HEF). The RNA strand is surrounded by protein and packaged in a lipoprotein membrane. Virions are capable of agglutinating erythrocytes and eluting into them using virus-specific enzymes.

The influenza virus has a spherical shape with a diameter of 80-120 nm, in the center there are RNA fragments enclosed in a lipoprotein shell, on the surface of which there are “spikes” consisting of hemagglutinin (H) and neuraminidase (N). Antibodies produced in response to hemagglutinin (H) form the basis of immunity against a specific subtype of influenza pathogen

The source of infection is a sick person with an obvious or erased form of the disease, releasing the virus by coughing, sneezing, etc. The patient is contagious from the first hours of the disease until the 5-7th day of the disease. It is characterized by an aerosol (inhalation of tiny drops of saliva, mucus that contain the influenza virus) transmission mechanism and extremely rapid spread in the form of epidemics and pandemics. Influenza epidemics caused by serotype A occur approximately every 2-3 years, and those caused by serotype B occur every 4-6 years. Serotype C does not cause epidemics, only isolated outbreaks in children and weakened people. It occurs more often in the form of epidemics in the autumn-winter period. The frequency of epidemics is associated with frequent changes in the antigenic structure of the virus during its stay in natural conditions.

The entry gates for the influenza virus are the cells of the ciliated epithelium of the upper respiratory tract - the nose, trachea, and bronchi. The virus multiplies in these cells and leads to their destruction and death. This explains irritation of the upper respiratory tract, coughing, sneezing, and nasal congestion. Penetrating into the blood and causing viremia, the virus has a direct, toxic effect, manifested in the form of fever, chills, myalgia, and headache. In addition, the virus increases vascular permeability, causes the development of stasis and plasma hemorrhages.

The traditional way to prevent influenza is vaccination. A vaccine has been proposed for the prevention of influenza in the form of a live, killed (inactivated), subunit vaccine. Vaccination is especially indicated in risk groups - children, elderly people, patients with chronic heart and lung diseases, as well as doctors. Usually carried out when the epidemiological forecast indicates the advisability of mass events (usually in mid-autumn). A second vaccination in mid-winter is also possible.

For quick diagnostics influenza tests use a “rapid method” for detecting the influenza virus using fluorescent antibodies. The test material is taken from the nose in the first days of the disease. Smears prepared from it are treated with specific fluorescent fluorescent sera. The resulting antigen-antibody complex glows brightly in the nucleus and cytoplasm of columnar epithelial cells and is clearly visible in a fluorescent microscope. The answer can be received in 2-3 hours.

Serological tests help retrospectively diagnose influenza. Paired blood sera taken from patients during the acute period of the disease (up to the 5th day from the onset of the disease) and during the period of convalescence with an interval of 12-14 days are examined. The most indicative in serological diagnostics are the complement fixation reaction (CFR) with influenza antigens and the hemagglutination inhibition reaction (HAI). An increase in antibody titer of 4 times or more is considered diagnostic.

Measles (lat. Morbilli)- an acute infectious viral disease with a high level of susceptibility (the contagiousness index approaches 100%), which is characterized by high fever (up to 40.5 °C), inflammation of the mucous membranes of the oral cavity and upper respiratory tract, conjunctivitis and a characteristic maculopapular rash of the skin , general intoxication.

The causative agent of measles is an RNA virus of the genus Morbillivirus, family of Paramyxoviruses, has a spherical shape and a diameter of 120-230 nm. It consists of a nucleocapsid - an RNA helix plus three proteins and an outer shell formed by matrix proteins (surface glycoproteins) of two types - one of them is hemagglutinin, the other is a “dumbbell-shaped” protein.

The virus is not stable in the external environment and quickly dies outside the human body from exposure to various chemical and physical factors (irradiation, boiling, treatment with disinfectants).

Despite its instability to the external environment, there are known cases of the virus spreading over significant distances with air flow through the ventilation system - during the cold season in one single building. Weakened strains of measles virus are used to produce live measles vaccine.

The route of transmission of infection is airborne; the virus is released into the external environment in large quantities by a sick person with mucus during coughing, sneezing, etc.

The source of infection is a patient with measles in any form, who is contagious to others from the last days of the incubation period (last 2 days) until the 4th day of rash. From the 5th day of the rash, the patient is considered non-infectious.

Measles affects mainly children aged 2-5 years and much less often adults who did not have this disease in childhood. Newborn children have colostral immunity, passed on to them from their mothers if they have previously had measles. This immunity lasts for the first 3 months of life. There are cases of congenital measles due to transplacental infection of the fetus with the virus from a sick mother.

After an illness, stable immunity develops; re-infection with measles in humans, without concomitant pathology of the immune system, is doubtful, although such cases have been described. Most cases of measles are observed in the winter-spring (December-May) period, with an increase in incidence every 2-4 years.

The incubation period is 8-14 days (rarely up to 17 days). Acute onset - temperature rise to 38-40 °C, dry cough, runny nose, photophobia, sneezing, hoarseness, headache, swelling of the eyelids and redness of the conjunctiva, hyperemia of the pharynx and measles enanthema - red spots on the hard and soft palate. On the 2nd day of illness, small whitish spots appear on the mucous membrane of the cheeks near the molars, surrounded by a narrow red border - Belsky-Filatov-Koplik spots - pathognomonic for measles. A measles rash (exanthema) appears on the 4-5th day of illness, first on the face, neck, behind the ears, the next day on the torso and on the 3rd day the rash covers the extensor surfaces of the arms and legs, including the fingers. The rash consists of small papules surrounded by a spot and prone to merging (this is its characteristic difference from rubella - the rash does not merge).

The reverse development of the elements of the rash begins on the 4th day of the rash - the temperature returns to normal, the rash darkens, turns brown, becomes pigmented, and peels off (in the same sequence as the rash). Pigmentation lasts 1-1.5 weeks.

Microbiological diagnostics. They examine swabs from the nasopharynx, scrapings from elements of the rash, blood, and urine. Measles virus can be detected in pathological material and in infected cell cultures using RIF, MRI and neutralization reaction. Characterized by the presence of multinucleated cells and pathogen antigens in them. For serological diagnosis, RSC, RTGA and neutralization reaction are used.

Specific prevention. Active specific prevention of measles is carried out by subcutaneous administration to children of the first year of life or live measles vaccine from attenuated strains, or an associated vaccine (against measles, mumps, rubella). In areas of measles, weakened children are given normal human immunoglobulin. The drug is effective when administered no later than the 7th day of the incubation period.

Parotitis(lat. parotitis epidemica: mumps, behind the ear) - an acute benign infectious disease, with non-purulent damage to the glandular organs (salivary glands, pancreas, testes) and the central nervous system, caused by paramyxovirus. The name "mumps" is considered obsolete. Nowadays this disease is more often called “mumps”. In Latin, the parotid salivary gland is called glandula parotidea, and its inflammation is mumps; => this is where the name of the disease comes from. Children aged 3 to 15 years are most often affected.

Infection occurs through airborne droplets (when coughing, sneezing, talking) from a sick person who is infected for up to 9 days.

Pathogen An RNA virus from the paramyxoviridae family. The causative agent of mumps was first isolated and studied in 1934 by E. Goodpasture and K. Johnson.

Virions are polymorphic, round virions have a diameter of 120-300 nm. Single-stranded and unfragmented minus RNA encodes 8 proteins, including the H-, N- and F-proteins of the supercapsid shell. The virus has hemagglutinating, neuraminidase and hemolytic activity.

After suffering mumps, persistent immunity remains.

Incubation period. The patient is contagious two days before the onset of the disease. Incubation period (from the moment of infection to the development of symptoms): 11 - 23 days; more often 13 - 19 days

Prevention. Vaccination: MMR associated vaccine (measles, mumps, rubella). Carried out at 12 months and 6 years.

Laboratory diagnostics. Virological and serological methods are used. Isolation of the virus from blood, saliva and cerebrospinal fluid is an indisputable confirmation of the diagnosis. In the hemagglutination inhibition reaction, antibodies (antihemagglutinins) to the EP virus are detected. Complement-fixing antibodies appear on the 2-5th day of illness and remain in the blood serum for a long time, which allows the use of CSC for both early and retrospective diagnosis. An increase in the titer of specific antibodies by 4 times or more is diagnostic. With a single serological examination during the period of convalescence, a titer of 1:80 or more is considered diagnostic.

Varicella (chickenpox) is an infectious disease caused by the herpes virus (Varicella-Zoster). Chickenpox is one of the most common and extremely contagious childhood infections. The causative agent of chickenpox is the herpes virus.

The main symptom of chickenpox in children is the appearance of small blistering rashes on the skin of the entire body. Treatment of chickenpox in children involves treating the rash with brilliant green. If the temperature is high, the child is given an antipyretic. Most often, children under 10 years of age suffer from chickenpox. As a rule, chickenpox is transmitted by airborne droplets. The source of infections are children with chickenpox. The incubation period for chickenpox ranges from 10 to 23 days. A characteristic manifestation of chickenpox in children is a rash. Chickenpox rashes in children are most often localized on the face and scalp. As chickenpox progresses, rashes appear all over the body. Chickenpox rashes are small red spots (1-5 mm). 2-5 days after the onset of chickenpox, bubbles (blisters) appear at the site of the spots. On the 7th day after the onset of chickenpox, the child ceases to be contagious. Within a few days, the bubbles burst and light brown crusts form in their place. As a rule, chickenpox rashes in children are accompanied by itching and increased body temperature (up to 39°C).

Diagnostics Chickenpox is diagnosed very simply by the appearance and nature of the rash. Diagnosis of chickenpox is possible after a physical examination, which is accompanied by a study of the patient's medical history.

For early laboratory diagnosis, the method of indirect immunofluorescence is used, as well as RSC in a later period.

Rubella(lat. rubella) or 3rd disease - an epidemic viral disease with an incubation period of about 15-24 days. It is usually a benign disease that mainly affects children, but it can cause serious birth defects if a woman becomes infected early in pregnancy. The name of the third disease comes from the time when a list of diseases causing childhood rash was compiled, in which it is listed third.

After an incubation period of 2-3 weeks, a moderate temperature appears with headache, pharyngitis, cervical adenopathy, and conjunctivitis. The rash appears after 48 hours, a macular (spotty) non-itchy rash, first on the face, then descends to the whole body within a few hours, at first the rash is morbiliform (reminiscent of measles), then scarlatinoform. It predominates on the face, in the lower back and buttocks, and on the extensor surfaces of the arms and legs. The rash lasts 2-4, occasionally 5-7 days, then disappears without pigmentation or peeling. It should be noted that mild and asymptomatic forms are quite common.

Pathogenesis. During a natural infection, the rubella virus enters the body through the mucous membranes of the respiratory tract, although in an experiment on volunteers it was possible to cause the disease with intradermal injection of the virus. Subsequently, viremia occurs. The virus spreads hematogenously throughout the body, has dermatotropic properties, and causes changes in the lymph nodes, which increase at the end of the incubation period. At this time, the virus can be isolated from the nasopharynx. With the appearance of the rash, the virus is not detected in the blood and nasopharynx, but in some cases its release continues for 1-2 weeks after the rash. Antibodies appear in the serum 1-2 days after the rash. Subsequently, their titer increases. After an illness, antibodies remain throughout life. The titer of complement-fixing antibodies gradually decreases. Immunity is stable for life.

Diagnosis Rubella can be confirmed either by isolating and identifying the virus, or by increasing titers of specific antibodies. For this purpose, various reactions are used: RSC, enzyme-linked immunosorbent assay, immunofluorescence reaction, as well as detection of specific class antibodies. Serological tests are performed with paired sera with an interval of 10-14 days. An increase in antibody titer by 4 times or more is diagnostic. Isolation and identification of the virus are quite complex and are almost never used in practical work.

Specific prevention. The live attenuated vaccine "Rudivax" is used, as well as the combined vaccine against measles, mumps, rubella - "MMR". In order to prevent congenital rubella, girls aged 12-16 years should be vaccinated, followed by revaccination of seronegative ones before a planned pregnancy.

Pregnant women cannot be vaccinated: pregnancy is undesirable for 3 months. after immunization against rubella (the possibility of post-vaccination damage to the fetus cannot be ruled out). Administration of the rubella vaccine is accompanied by the production of specific antibodies in 95% of immunized individuals.

In case of contact of a pregnant woman with a patient with rubella, the question of maintaining pregnancy should be decided taking into account the results of a 2-fold serological examination (with the obligatory determination of the quantitative content of specific immunoglobulins of classes M and G). If a pregnant woman has a stable titer of specific antibodies, contact should be considered not dangerous.

TEST TASKS
1. Avian influenza virus is

a) to influenza virus type C

b) to influenza virus type A

c) to influenza virus type B

d) to influenza virus type D
2. What type of nucleic acid does the measles virus contain?

c) DNA and RNA.

a) DNA genomic;

b) RNA genomic;

c) complex.

prevents:

c) virus reproduction;

d) lysis of the affected cell;

e) activation of killers.
5. The serological type of influenza virus can be determined using:

a) agglutination reactions on glass;

b) hemagglutination inhibition reactions;

c) indirect hemagglutination reactions;

d) hemagglutination reactions.

LABORATORY WORK No. 14

SUBJECT: VIRUSES CAUSES CONTACT INFECTIONS

(rabies pathogens, herpes viruses).
Learning objective:

1. Train students in virological diagnostic methods and

specific prevention of rabies, herpes.
The student must know:
1.Biological properties and laboratory diagnostics of rabies, herpes.

2. Specific prevention of rabies, herpes.

– Giemsa, for the detection of Babes-Negri inclusions in rabies.

2. Set up and take into account the results of ELISA for the serodiagnosis of herpes.

PLAN:

1. 
   Taxonomy and basic biological properties of pathogens

1. 
   Epidemiology, pathogenesis, immunity of caused diseases.
2. 
   Principles of microbiological diagnosis of rabies, herpes.
3. 
   Preparations for etiotropic therapy and specific prevention of rabies and herpes.

INDEPENDENT WORK

Positive results are due to the migration of the virus from the brain along nerve fibers, which are rich in the cornea and hair follicles.

Serological diagnosis is possible in patients who have recovered from the acute phase of the disease.

Neutralizing antibodies appear in the blood and cerebrospinal fluid, the concentration of which can reach very high levels. They use RN, RSK, RPGA.

Herpes(Greek ἕρπης - creeping, spreading skin disease) is a viral disease with a characteristic rash of grouped blisters on the skin and mucous membranes.

Herpes simplex is a group of crowded blisters with transparent contents on an inflamed base. Herpes is preceded by itching, burning of the skin, sometimes chills, and malaise.

Shingles (Herpes zoster) - characterized by pain along the nerve, headache. After a few days, rashes appear on the skin along the nerve in the form of grouped blisters, first with transparent and then with purulent bloody contents. Lymph nodes enlarge, body temperature rises, and general condition is disturbed. Neuralgic pain can last up to several months.

Pathogenesis. The herpes virus is transmitted by direct contact, as well as through household items. Airborne transmission of infection is also possible. Herpes penetrates through the mucous membranes of the mouth, upper respiratory tract and genitals. Having overcome tissue barriers, the virus enters the blood and lymph. Then it enters various internal organs.

The virus penetrates sensitive nerve endings and integrates into the genetic apparatus of nerve cells. After this, it is impossible to remove the virus from the body; it will remain with the person for life. The immune system responds to the penetration of herpes by producing specific antibodies that block viral particles circulating in the blood. The awakening of infection is typical in the cold season, with colds, and with hypovitaminosis. Reproduction of herpes in epithelial cells of the skin and mucous membranes leads to the development of dystrophy and cell death.

According to research by Columbia University scientists, herpes is a stimulating factor for the development of Alzheimer's disease. These data were later independently confirmed by researchers from the University of Manchester. Previously, the same group of researchers led by Ruth Itzhaki proved that the herpes simplex virus is found in the brains of almost 70% of patients with Alzheimer's disease. In addition, they confirmed that when a brain cell culture is infected with a virus, there is a significant increase in the level of beta-amyloid, from which plaques are formed. In a recent study, scientists were able to find that 90% of plaques in the brains of patients with Alzheimer's disease contain DNA from herpes simplex - HSV-1.

To diagnose herpes infection, all laboratory reactions are used - from cytological studies to molecular biological methods.

The material for isolating the virus for the purpose of diagnosing a herpetic infection can be the contents of herpetic vesicles, scrapings from the cornea and fluid from the anterior chamber of the eye, blood, saliva, urine, cerebrospinal fluid, feces, pieces of tissue from the brain, liver, kidneys, spleen, lungs, lymph nodes taken for bio- or autopsy.

Infectious material can be stored for a long time at -70°C, whereas at a temperature of -20°C it is quickly inactivated. Virus-containing tissues can be stored for more than 6 months at 4°C if they are in a 50% glycerol solution.

There are a number of special methods for identifying viral antigens, specific antibodies and virus-induced morphologically altered cells.

The most accessible and technically simple method is the cytological method, which allows one to study morphological changes in cells infected with the herpes simplex virus. The effectiveness of the method depends on obtaining a sufficient number of cells for research. The presence of intranuclear inclusions, characteristic of the reproduction of the herpes virus, confirms the diagnosis. It should be remembered that intranuclear inclusions are detected only after immediate fixation of scraping smears in absolute alcohol, followed by Romanovsky-Giemsa staining. Morphological changes induced by the herpes simplex virus can also be detected in tissue sections of infected organs. Characteristic of herpetic infection is the presence of multinucleated cells, intranuclear inclusions and, in some cases, hemorrhage. In the generalized form of the disease, multinucleated cells with eosinophilic inclusions are found in areas of necrotic tissue of various organs (brain, liver, kidneys, adrenal glands, bronchial and tracheal epithelium).

The immunofluorescence method is a method for express diagnosis of herpes infection and allows you to determine the presence of herpesvirus antigens in clinical material (scrapings from the skin and mucous membranes, sections of biopsied organs) within 1-2 hours. Identification of herpes simplex virus antigens can be performed in various modifications of the immunofluorescence method - direct, indirect, using labeled complement.

Of the serological identification methods, the complement fixation reaction (CFR) is most often used, especially in its micromodification. Micromethods are also used to detect herpes simplex virus in neutralization reactions, passive hemagglutination and other serological tests. The sensitivity of these methods varies.

Currently, one of the most sensitive methods for diagnosing herpes infection is the enzyme-linked immunosorbent assay (ELISA), which makes it possible to detect, depending on the type of biological material, both virus-specific antigens and virus-specific antibodies of the IgM, IgG class.

TEST TASKS
1. What type of nucleic acid does the rabies virus contain?

c) DNA and RNA.

2. What type of nucleic acid does the herpes virus contain?

c) DNA and RNA.

a) DNA genomic;

b) RNA genomic;

c) complex.

prevents:

a) adsorption of the virus on the cell;

b) penetration of the virus into the cell;

c) virus reproduction;

d) lysis of the affected cell;

e) activation of killers.
5. In the pathogenesis of viral diseases, a decisive role is played by:

a) virulence of the virus;

b) toxigenicity of the virus;

d) lysozyme level;

e) the body’s reaction to cells affected by the virus.

In the course of our discipline, we do not consider treatment issues in detail. This is the task of clinical departments, but you should have an understanding of the most general principles of treatment of infectious diseases. Treatment of all diseases, including infectious ones, can be of three types: symptomatic, pathogenetic and etiotropic.

Simp tomato lech Treatment is based on the use of medicinal drugs in accordance with the symptoms of the disease - for pain - give analgesics, for elevated temperatures - antipyretics, etc. Usually, when applying symptomatic treatment, we try to alleviate the patient’s condition, often without taking into account the etiology and mechanism of development of the pathological syndrome. Strictly speaking, if symptomatic treatment has an effect, it becomes pathogenetic.

Patoge netic therapy I am aimed at normalizing the disturbed physiological functions of the body. This is one of the essential ways to treat infectious diseases. In some cases, in the absence of etiotropic therapy, correctly carried out pathogenetic treatment is the main one, for example, in the treatment of most viral diseases. Pathogenetic therapy also plays a significant role in bacterial infections.

For example m Er, in cholera, the leading link in pathogenesis is tissue dehydration due to the action of cholera exotoxin, choleragen. Only properly carried out rehydration therapy ensures the success of treatment, and we are not talking about simply administering fluids through drinking or parenterally. At the Department of Infectious Diseases, you should become familiar with this method of treatment in detail; this is all the more important since the department’s employees have experience working during the last cholera pandemic.

etiotr opnaya therapy The analysis is aimed at the cause of the disease - the etiological factor, the pathogen and the products of its vital activity and decay. Specific ical etiotropic therapy - treateni e serum preparations, immune sera and immunoglobulins, from which antibodies act specifically on the pathogen and its toxins. With some reservations, vaccine therapy should be considered a specific etiotropic therapy. However, in vaccine therapy for chronic diseases of microbial etiology, the therapeutic effect is usually achieved due to both specific stimulation of the immune system and a significant nonspecific stimulating effect. Phage therapy is also a specific etiotropic therapy, but it is currently used relatively rarely.

Nespets ific etiotropic therapy - treatment e antimicrobial drugs (antibiotics, sulfonamides, chemotherapy drugs). Please note that antibiotic treatment is not a specific therapy method, since there is not a single antibiotic that affects only one type of pathogen.

When independently studying individual topics, it is necessary to pay attention mainly to specific etiotropic therapy, since antibiotic therapy is used for almost all bacterial infections.

5. Principles of prevention of infectious diseases The main direction of modern medicine is preventive. Prevention of infectious diseases is carried out through measures aimed at breaking the epidemic esky chain: source IC infection - transmission mechanism - susceptible population. Prevention can be specific and nonspecific.

Specific European prevention is carried out when using specific drugs: vaccines, serums, phages. Active immunization with vaccines is of greatest importance. At the last lecture on the course of immunology, we discussed the issues of vaccine prevention, we only remind you that vaccination rophylaxis happens planned and for epidemiological indications. We always pay attention, first of all, to your knowledge of vaccines used for routine prevention. It will be useful to learn the routine vaccination calendar adopted in Ukraine once and for a long time; it will be useful not only for studying our subject, but also in the future. Seroprfi lactic mainly om is used for emergency prevention of disease in persons for whom the risk of infection is high. When studying each topic, it is necessary to pay attention to the use of vaccines and serums for the prevention of diseases, since this constitutes an important section of our discipline.

We emphasize that specific prevention is aimed at breaking the epidemic chain at the last link; it should make the population immune to the corresponding infectious disease.

Non-specific ical prevention consisting of There is a set of measures that are the same for the prevention of all infectious diseases with the same route of transmission. It is aimed at all three links of the epidemic chain.

Impact on the first link - source And infections, conclude is in the early detection, isolation and treatment of patients and carriers. Identification of patients is not only the diagnosis of diseases in patients who have sought medical help, but also a targeted systematic examination of decreed populations for intestinal infections, sexually transmitted diseases, hepatitis, AIDS, etc. Isolation of identified patients is carried out in infectious diseases hospitals and at home, in student dormitories - in isolators, etc. Isolation can also include separation - the closure of children's institutions for quarantine, a ban on visiting hospitals, the cancellation of mass events during an epidemic (for example, influenza), etc. The entire range of measures, including those for especially dangerous infections, will be discussed in more detail at the Department of Epidemiology .

Impact on the second link of the chain - mechanisms and transmission factors, conducts varies depending on the route of transmission. To interrupt fecal-o ral way of transfer In order to avoid infection, it is important to ensure sanitary control of water supply and sewerage in populated areas, public catering networks, monitor compliance with sanitary and hygienic standards in trade, food production, combat the spread of flies (timely door-to-door garbage collection, use of lockable containers for garbage collection), etc. Current and final disinfection is important. Air-to interruption appeal route dachas are possible due to the separation of the population, wearing gauze masks, ventilation and treatment with ultraviolet rays (quartzization) of indoor air, etc. Transmission path the dacha is interrupted by destroying blood-sucking insects and treating their breeding sites (for example, for malaria, as discussed in the biology course), using repellents, cutting off windows, etc. Contact way in front achi is interrupted by maintaining personal hygiene and sanitation at home, using condoms to prevent the transmission of sexually transmitted diseases, etc. Transmission of infection t transplacental is interrupted by monitoring pregnant women for a number of diseases (syphilis, AIDS) transmitted from mother to fetus. We are now naming only some methods of nonspecific prevention; this material will be presented in full by students at the Department of Epidemiology.

The third link of the epidemic chain is susceptible population. Its protection against infection should primarily consist of sanitary and educational work. People should be notified of the unfavorable epidemiological situation through television, radio, newspapers, health bulletins in clinics, leaflets, posters, etc. In some cases, emergency nonspecific drug prophylaxis is carried out (with antibiotics, antimalarial drugs), which is essentially preventive therapy after a possible infection.

You need to understand that none of the preventive measures taken ensures 100% success, therefore prevention must be comprehensive, using all the possibilities of specific and nonspecific prevention.6. DIAGNOSIS OF INFECTIOUS DISEASES

The microbiological service in the practical healthcare system mainly performs the task of microbiological diagnosis of infectious diseases and non-infectious diseases of microbial etiology. In practical classes, students study methods of microbiological diagnosis of specific diseases, taking into account the characteristics of the biological properties of the pathogen and the course of the disease. At the lecture we will look at the general principles of microbiological diagnostics and its place in the diagnostic activity of a doctor.

Diagnosis of an infectious disease, like any other, begins with anamnesis. Next comes an objective (inspection, palpation, percussion, auscultation) and instrumental examination (temperature measurement, ECG, endoscopic, x-ray, ultrasound, etc.), clinical and laboratory (blood, urine, stool tests, biochemical, cytological examinations, etc.) . In addition to these methods, when making a diagnosis of an infectious disease, it is also necessary to take into account the epidemiological situation at that time and in that area. In areas where certain infections are endemic, the direction of the diagnostic search will be appropriate. During an epidemic of an infectious disease, of course, first of all, differential diagnosis will be carried out, taking into account alertness regarding influenza, typhoid fever, cholera, etc. It is clear that we began to think about AIDS as a possible diagnosis only now that we know the epidemiological situation in the world and in our country.

Typically, the use of these diagnostic methods should lead to the establishment of a preliminary diagnosis and the prescription of treatment and an appropriate anti-epidemic regimen. Microbiological examination at this stage does not always help diagnosis, since it takes a long time, and rapid methods play only a supporting role. Therefore, most often treatment begins before an accurate diagnosis is established and without using the results of microbiological studies.

I would like to emphasize that the diagnosis of a disease is made not by a laboratory, but by a clinician. I do not want to belittle the importance of my specialty, but it is important to understand that the responsibility for the correct management of the patient lies with you, the future practicing physicians. And in order to make an accurate, timely diagnosis and prescribe adequate therapy, you need to skillfully use the results of microbiological studies, know their capabilities and limitations, choose the right time to prescribe a specific study and the material to be studied, be able to collect it and send it to the microbiological laboratory.

We must outline the basic principles of microbiological diagnostics, which you must clearly understand. In the future, when studying individual infections, you will use these general principles for a better understanding and memorization of the material, paying attention to the main differences between the diagnosis of an individual disease and classical microbiological diagnostic schemes. This way of studying educational material is the most effective.

First of all, we note that the only one The basis for making a microbiological diagnosis of any infectious disease is the direct or indirect detection of the pathogen in the body. For clarity, we show you a table of the main methods for microbiological diagnosis of bacterial infections (Table 1).

Direct determination of the pathogen in the body and its identification (determination of species) is possible using microscopic, bacteriological and biological diagnostic methods. It is necessary to distinguish between the terms “diagnosis” and “research”. If the term “microscopic diagnosis” is used, this means that a microbiological diagnosis is established on the basis of a microscopic examination of material from a patient; a pathogen was detected in this material by microscopy and identified by morphological and tinctorial properties. Accordingly, the reliability of the diagnosis can be assessed.

Microscopic examination can be not only an independent method of establishing a diagnosis, but also a stage of other research and diagnostic methods. For example, during bacteriological diagnostics, a microscopic examination of smears from the material being studied, a colony, or an isolated pure culture is repeatedly carried out, but the basis for the diagnosis is the isolation of the culture and its identification by a set of properties. Likewise, a serological study can be a stage in the identification of an isolated pure culture, but serological diagnosis is an independent diagnostic method. In accordance with this, we determine methods for diagnosing bacterial infections.

Microbiological diagnostics begins with the collection of test material. Material under study There may be patient discharge (feces, urine, sputum, pus, mucous discharge), biopsy material (blood, cerebrospinal fluid, pieces of tissue taken during surgery or examination), autopsy material taken during an autopsy. Sometimes environmental objects are subjected to microbiological research - water, food, soil, air, material from animals. The taken material is accompanied by a referral to the laboratory, and proper transportation and storage of the studied material is ensured.

Table 1.

BASIC METHODS OF MICROBIOLOGICAL DIAGNOSTICS

No. 33 Pathogens of ARVI. Taxonomy. Characteristic. Laboratory diagnostics. Specific prevention and treatment.
Taxonomy and classification: RNA viruses. Family I - Paramyxoviridae includes human parainfluenza viruses (5 serotypes) and respiratory syncytial virus (RS);
Family II - Picomaviridae includes 7 serotypes of Coxsackie and ECHO enteroviruses that affect the respiratory tract, and 120 serotypes of rhinoviruses;
Family III - Reoviridae includes 3 serotypes that cause diseases of the respiratory and gastrointestinal tracts;
Family IV - Coronaviridae includes 3 serotypes, also affecting the respiratory and gastrointestinal tracts.
DNA viruses. Family V - Adenoviridae. Representatives of this family affect the eyes, intestines, and bladder; 3 types of adenoviruses cause ARVI.
Structure: . Medium size, spherical, rod-shaped or thread-like. Most ARVI pathogens contain single-stranded RNA, except for reoviruses, which have double-stranded RNA, and DNA-containing adenoviruses. Some of them are surrounded by a supercapsid.
Antigenic structure : difficult. Viruses of each genus have common antigens; viruses also have type-specific antigens, which can be used to identify pathogens and determine the serotype. Each group of ARVI viruses includes a different number of serotypes and serovars. Most ARVI viruses have hemagglutinating ability. RTGA is based on blocking the activity of virus hemagglutinins with specific antibodies.
Cultivation : Optimal model for cultivation - cell culture. For each group of viruses, the most sensitive cells were selected (for adenoviruses, embryonic kidney cells; for coronaviruses, embryonic cells and tracheal cells). In infected cells, viruses cause CPE (cytopathic effect). Cell cultures are also used to identify pathogens with cytolytic activity (for example, adenoviruses). For this purpose, the so-called reaction of biological neutralization of viruses in cell culture (RBN or RN of viruses) is used. It is based on neutralization of the cytolytic effect of viruses by type-specific antibodies.
Immunity: virus-neutralizing specific IgA (provide local immunity) and cellular immunity. Local production of a-interferon, the appearance of which in nasal discharge leads to a significant decrease in the number of viruses. An important feature of ARVI is the formation of secondary immunodeficiency. Post-infectious immunity is unstable, short-lived, and type-specific. A large number of serotypes and a variety of viruses means a high frequency of recurrent diseases.
Microbiological diagnostics. Material for research: nasopharyngeal mucus, fingerprint swabs and swabs from the throat and nose.
Express diagnostics. Detect viral antigens in infected cells. RIF (direct and indirect methods) is used using fluorochrome-labeled specific antibodies, as well as ELISA. For difficult-to-cultivate viruses, the genetic method (PCR) is used.
Virological method. Indication of viruses in infected laboratory models is carried out by CPE, as well as RHA and hemadsorption (for viruses with hemagglutinating activity), by the formation of inclusions (intranuclear inclusions in adenovirus infection, cytoplasmic inclusions in the perinuclear zone in reovirus infection, etc.), as well as by the formation of “plaques” and “color test”. Viruses are identified by antigenic structure in RSK, RPGA, ELISA, RTGA, RBN viruses.
Serological method. Antiviral antibodies are tested in paired patient sera obtained with an interval of 10 days. The diagnosis is made when the antibody titer increases at least 4 times. In this case, the level of IgG is determined in such reactions as RBN viruses, RSK, RPGA, RTGA.
Treatment: effective etiotropic - no; nonspecific - a-interferon, oxolin (eye drops), for secondary bacterial infection - antibiotics. The main treatment is symptomatic/pathogenetic. Antihistamines.
Prevention: nonspecific – anti-epidemic. Events. Specific - no. For the prevention of adenoviruses - oral live trivalent vaccines.

– a science whose subject of study is microscopic creatures called microorganisms, their biological characteristics, taxonomy, ecology, relationships with other organisms.

Microorganisms- the most ancient form of organization of life on Earth. In terms of quantity, they represent the most significant and most diverse part of the organisms inhabiting the biosphere.

Microorganisms include:

1) bacteria;

2) viruses;

4) protozoa;

5) microalgae.

Bacteria are single-celled microorganisms of plant origin, lacking chlorophyll and lacking a nucleus.

Fungi are unicellular and multicellular microorganisms of plant origin, lacking chlorophyll, but having the features of an animal cell, eukaryote.

Viruses are unique microorganisms that do not have a cellular structural organization.

Main sections of microbiology: general, technical, agricultural, veterinary, medical, sanitary.

General microbiology studies the most general patterns inherent in each group of listed microorganisms: structure, metabolism, genetics, ecology, etc.

The main task of technical microbiology is the development of biotechnology for the synthesis by microorganisms of biologically active substances: proteins, enzymes, vitamins, alcohols, organic substances, antibiotics, etc.

Agricultural microbiology deals with the study of microorganisms that participate in the cycle of substances, are used to prepare fertilizers, cause plant diseases, etc.

Veterinary microbiology studies pathogens of animal diseases, develops methods for their biological diagnosis, specific prevention and etiotropic treatment aimed at destroying pathogenic microbes in the body of a sick animal.

The subject of study of medical microbiology is pathogenic (pathogenic) and conditionally pathogenic microorganisms for humans, as well as the development of methods for microbiological diagnosis, specific prevention and etiotropic treatment of infectious diseases caused by them.

The subject of study of sanitary microbiology is the sanitary and microbiological state of environmental objects and food products, the development of sanitary standards.

2. Systematics and nomenclature of microorganisms

The basic taxonomic unit of bacterial taxonomy is the species.

A species is an evolutionarily established set of individuals that have a single genotype, which under standard conditions is manifested by similar morphological, physiological, biochemical and other characteristics.

The species is not the final unit of taxonomy. Within a species, there are variants of microorganisms that differ in certain characteristics:

1) serovars (by antigenic structure);

2) chemovars (according to sensitivity to chemicals);

3) phage products (based on sensitivity to phages);

4) fermenters;

5) bacteriocinovars;

6) bacteriocinogenovars.

Bacteriocins are substances produced by bacteria and have a detrimental effect on other bacteria. Bacteriocinovars are distinguished according to the type of bacteriocin produced, and bactericinogenovars are distinguished according to sensitivity.

Properties of bacteria:

1) morphological;

2) tinctorial;

3) cultural;

4) biochemical;

5) antigenic.

Species are grouped into genera, genera into families, families into orders. Higher taxonomic categories are classes, divisions, subkingdoms and kingdoms.

Pathogenic microorganisms belong to the kingdom of prokaryotes, pathogenic protozoa and fungi belong to the kingdom of eukaryotes, viruses are united in a separate kingdom - Vira.

All prokaryotes that have a single type of cell organization are united into one department - Bacteria, in which they distinguish:

1) bacteria themselves;

2) actinomycetes;

3) spirochetes;

4) rickettsia;

5) chlamydia;

6) mycoplasma.

For taxonomy of microorganisms the following are used:

1) numeric taxonomy. Recognizes the equivalence of all characteristics. Species affiliation is established by the number of matching characteristics;

2) serotaxonomy. Studies bacterial antigens using reactions with immune sera;

3) chemotaxonomy. Physicochemical methods are used to study the lipid and amino acid composition of the microbial cell and certain of its components;

4) gene systematics. It is based on the ability of bacteria with homologous DNA to transform, transduce and conjugate, and on the analysis of extrachromosomal factors of heredity - plasmids, transposons, phages.

A pure culture is bacteria of one species grown on a nutrient medium.

3. Nutrient media and methods for isolating pure cultures

For the cultivation of bacteria, nutrient media are used, which have a number of requirements.

1. Nutritional value. The bacteria must contain all the necessary nutrients.

2. Isotonicity. Bacteria must contain a set of salts to maintain osmotic pressure, a certain concentration of sodium chloride.

3. Optimal pH (acidity) of the environment. The acidity of the environment ensures the functioning of bacterial enzymes; for most bacteria it is 7.2–7.6.

4. Optimal electronic potential, indicating the content of dissolved oxygen in the medium. It should be high for aerobes and low for anaerobes.

5. Transparency (so that bacterial growth is visible, especially for liquid media).

6. Sterility.

Classification of nutrient media.

1. By origin:

1) natural (milk, gelatin, potatoes, etc.);

2) artificial - media prepared from specially prepared natural components (peptone, aminopeptide, yeast extract, etc.);

3) synthetic - media of known composition, prepared from chemically pure inorganic and organic compounds.

2. By composition:

1) simple – meat-extract agar, meat-extract broth;

2) complex - these are simple with the addition of an additional nutrient component (blood, chocolate agar): sugar broth, bile broth, whey agar, yolk-salt agar, Kitta-Tarozzi medium.

3. By consistency:

1) solid (contain 3–5% agar-agar);

2) semi-liquid (0.15-0.7% agar-agar);

3) liquid (do not contain agar-agar).

4. By purpose:

1) general purpose – for cultivating most bacteria (meat agar, meat agar, blood agar);

2) special purpose:

a) selective - media on which bacteria of only one species (genus) grow, and the genus of others is suppressed (alkaline broth, 1% peptone water, yolk-salt agar, casein-charcoal agar, etc.);

b) differential diagnostic - media on which the growth of some types of bacteria differs from the growth of other species in certain properties, often biochemical (Endo, Levin, Gis, Ploskirev, etc.);

c) enrichment environments - environments in which the reproduction and accumulation of pathogenic bacteria of any kind or type occurs (selenite broth).

To obtain a pure culture, it is necessary to master the methods of isolating pure cultures:

1. Mechanical separation (stroke method by firing a loop, dilution method in agar, distribution over the surface of a solid nutrient medium with a spatula, Drigalsky method).

2. Use of elective nutrient media.

A colony is an isolated collection of bacteria visible to the naked eye on a solid nutrient medium.

4. Morphology of bacteria, main organs

The sizes of bacteria range from 0.3–0.5 to 5–10 microns.

Based on the shape of the cells, bacteria are divided into cocci, rods and convoluted.

In a bacterial cell there are:

1) main organelles: (nucleoid, cytoplasm, ribosomes, cytoplasmic membrane, cell wall);

2) additional organelles (spores, capsules, villi, flagella)

Cytoplasm is a complex colloidal system consisting of water (75%), mineral compounds, proteins, RNA and DNA.

Nucleoid is a nuclear substance dispersed in the cytoplasm of the cell. It does not have a nuclear membrane or nucleoli. This is pure DNA and does not contain histone proteins. The nucleoid encodes the basic genetic information, i.e., the genome of the cell.

The cytoplasm may contain autonomous circular DNA molecules with a lower molecular weight - plasmids.

Ribosomes are ribonucleoprotein particles 20 nm in size, consisting of two subunits - 30 S and 50 S. Ribosomes are responsible for protein synthesis.

Mesosomes are derivatives of the cytoplasmic membrane. Mesosomes can be in the form of concentric membranes, vesicles, and tubes.

The cell wall is an elastic, rigid formation 150–200 angstroms thick. Performs the following functions:

1) protective, implementation of phagocytosis;

2) regulation of osmotic pressure;

3) receptor;

4) takes part in the processes of nutrition of cell division;

5) antigenic;

6) stabilizes the shape and size of bacteria;

7) provides a system of communications with the external environment;

8) indirectly participates in the regulation of cell growth and division.

Depending on the content of murein in the cell wall, gram-positive and gram-negative bacteria are distinguished.

In gram-positive bacteria, the murein layer makes up 80% of the mass of the cell wall. According to Gram, they are colored blue. In Gram-positive bacteria, the murein layer makes up 20% of the mass of the cell wall; according to Gram, they are stained red.

Cytoplasmic membrane. It has selective permeability, takes part in the transport of nutrients, the removal of exotoxins, the energy metabolism of the cell, is an osmotic barrier, and is involved in the regulation of growth and division, and DNA replication.

It has a normal structure: two layers of phospholipids (25–40%) and proteins.

Based on their function, membrane proteins are divided into:

1) structural;

2) permiases – proteins of transport systems;

3) enzymes – enzymes.

The lipid composition of membranes is not constant. It may vary depending on cultivation conditions and age of the crop.

5. Morphology of bacteria, additional organelles

Villi(pili, fimbriae) are thin protein projections on the surface of the cell wall. Comon pili are responsible for the adhesion of bacteria to the surface of cells of the macroorganism. They are characteristic of gram-positive bacteria. Sex pili mediate contact between male and female bacterial cells through the process of conjugation. Through them, genetic information is exchanged from donor to recipient.

Flagella- organelles of movement. These are special protein outgrowths on the surface of the bacterial cell containing the protein flagellin. The number and location of flagella can be different:

1) monotrichs (have one flagellum);

2) lophotrichs (have a bundle of flagella at one end of the cell);

3) amphitrichy (have one flagellum at each end);

4) peritrichous (have several flagella around the perimeter).

The mobility of bacteria is judged by examining living microorganisms, or indirectly by the nature of growth in Peshkov’s medium (semi-liquid agar). Immobile bacteria grow strictly according to the puncture, while mobile bacteria grow diffusely.

Capsules represent an additional surface shell. The function of the capsule is protection against phagocytosis and antibodies.

There are macro- and microcapsules. The macrocapsule can be identified using special staining methods, combining positive and negative staining methods. Microcapsule is a thickening of the upper layers of the cell wall. It can only be detected by electron microscopy.

Among the bacteria there are:

1) true capsule bacteria (genus Klebsiella) – retain capsule formation even when growing on nutrient media, and not only in the macroorganism;

2) false capsules - they form a capsule only when they enter the macroorganism.

Capsules can be polysaccharide and protein. They play the role of an antigen and can be a virulence factor.

Spores are special forms of existence of certain bacteria under unfavorable environmental conditions. Sporulation is characteristic of gram-positive bacteria. Unlike vegetative forms, spores are more resistant to chemical and thermal factors.

Most often, spores are formed by bacteria of the genus Bacillus And Clostridium.

The process of sporulation involves the thickening of all cell membranes. They become saturated with calcium dipicalinate salts, become dense, the cell loses water, and all its plastic processes slow down. When the spore finds itself in favorable conditions, it germinates into a vegetative form.

Gram-negative bacteria have also been shown to persist in unfavorable conditions in the form of uncultivable forms. In this case, there is no typical sporulation, but metabolic processes in such cells are slowed down, and it is impossible to immediately obtain growth on a nutrient medium. But when they enter the macroorganism, they transform into their original forms.

6. Growth, reproduction, nutrition of bacteria

Bacterial growth– an increase in bacterial cell size without increasing the number of individuals in the population.

Bacteria reproduction– a process that ensures an increase in the number of individuals in a population. Bacteria are characterized by a high reproduction rate.

Bacteria reproduce by transverse binary fission.

On solid nutrient media, bacteria form clusters of cells - colonies. In liquid media, bacterial growth is characterized by the formation of a film on the surface of the nutrient medium, uniform turbidity or sediment.

Phases of bacterial cell reproduction on a liquid nutrient medium:

1) initial stationary phase (the amount of bacteria that entered the nutrient medium and remains in it);

2) lag phase (resting phase) (active cell growth begins, but there is no active reproduction yet);

3) phase of logarithmic reproduction (cell reproduction processes in the population are actively underway);

4) maximum stationary phase (bacteria reach maximum concentration; the number of dead bacteria is equal to the number of new ones);

5) phase of accelerated death.

Under food understand the processes of entry and exit of nutrients into and out of cells.

Among the essential nutrients are organogens (carbon, oxygen, hydrogen, nitrogen, phosphorus, potassium, magnesium, calcium).

Depending on the source of carbon, bacteria are divided into:

1) autotrophs (use inorganic substances - CO 2 );

2) heterotrophs;

3) metatrophs (use organic substances of inanimate nature);

4) paratrophs (use organic substances of living nature).

Based on energy sources, microorganisms are divided into:

1) phototrophs (able to use solar energy);

2) chemotrophs (obtain energy through redox reactions);

3) chemolithotrophs (use inorganic compounds);

4) chemoorganotrophs (use organic substances).

Pathways for metabolites and ions to enter the microbial cell.

1. Passive transport (without energy costs):

1) simple diffusion;

2) facilitated diffusion (along the concentration gradient).

2. Active transport (with energy consumption, against the concentration gradient; in this case, the substrate interacts with the carrier protein on the surface of the cytoplasmic membrane).

7. Types of bacterial metabolism

In the process of metabolism, there are two types of exchange:

1) plastic (structural):

a) anabolism (with energy expenditure);

b) catabolism (with the release of energy);

2) energy metabolism (occurs in respiratory mesosomes):

a) breathing;

b) fermentation.

Energy exchange

Depending on the acceptor of protons and electrons, bacteria are divided into aerobes, facultative anaerobes and obligate anaerobes. For aerobes, oxygen is the acceptor.

The following enzymes are distinguished according to the site of action:

1) exoenzymes (act outside the cell);

2) endoenzymes (act in the cell itself).

Depending on the chemical reactions they catalyze, all enzymes are divided into six classes:

1) oxidoreductases (catalyze redox reactions between two substrates);

2) transferases (carry out intermolecular transfer of chemical groups);

3) hydrolases (carry out hydrolytic cleavage of intramolecular bonds);

4) lyases (attach chemical groups to two bonds);

5) isomerases (carry out isomerization processes, provide internal conversion with the formation of various isomers);

6) ligases, or synthetases (they connect two molecules, resulting in the cleavage of pyrophosphate bonds in the ATP molecule).

4. Types of plastic metabolism (protein, carbohydrate, lipid, nucleic acid).

Protein metabolism is characterized by catabolism and anabolism. In the process of catabolism, bacteria decompose proteins under the action of proteases to form peptides. Under the action of peptidases, amino acids are formed from peptides.

In carbohydrate metabolism in bacteria, catabolism prevails over anabolism. Polysaccharides are broken down into disaccharides, which are broken down into monosaccharides by the action of oligosaccharidases.

Depending on the final products, the following types of fermentation are distinguished:

1) alcohol (typical for mushrooms);

2) propionionic acid (characteristic of clostridia);

3) lactic acid (characteristic of streptococci);

4) butyric acid (characteristic of sarcinas);

5) butyldene glycol (typical for bacilli).

Lipid metabolism is carried out with the help of enzymes - lipoproteinases, leticinases, lipases, phospholipases.

Lipases catalyze the breakdown of neutral fatty acids. When fatty acids are broken down, the cell stores energy.

The nucleic exchange of bacteria is associated with genetic exchange. The synthesis of nucleic acids is important for the process of cell division. Synthesis is carried out using enzymes: restriction enzyme, DNA polymerase, ligase, DNA-dependent RNA polymerase.

8. Genetics of macroorganisms

The hereditary apparatus of bacteria is represented by one chromosome, which is a DNA molecule.

The functional units of the bacterial genome, in addition to chromosomal genes, are: IS sequences, transposons, plasmids.

IS sequences are short fragments of DNA. They do not carry structural (protein-coding) genes, but contain only genes responsible for transposition.

Transposons are larger DNA molecules. In addition to the genes responsible for transposition, they also contain a structural gene. Transposons are capable of moving along a chromosome.

Plasmids are additional extrachromosomal genetic material. It is a circular, double-stranded DNA molecule, the genes of which encode additional properties, giving selective advantages to cells. Plasmids are capable of autonomous replication.

Depending on the properties of the traits that plasmids encode, they are distinguished:

1) R-plasmids. Provide drug resistance; may contain genes responsible for the synthesis of enzymes that destroy drugs, may change membrane permeability;

2) F-plasmids. They code sex in bacteria. Male cells (F+) contain the F plasmid, female cells (F-) do not;

3) Col plasmids. Encode the synthesis of bacteriocins;

4) Tox plasmids. Encodes the production of exotoxins;

5) biodegradation plasmids. Encode enzymes with which bacteria can utilize xenobiotics.

Variability in bacteria:

1. Phenotypic variability - modifications - does not affect the genotype. They are not inherited and fade over time.

2. Genotypic variation affects the genotype. It is based on mutations and recombinations.

Mutations are a change in the genotype that persists over a number of generations and is accompanied by a change in phenotype. A feature of mutations in bacteria is the relative ease of their detection.

Recombination is the exchange of genetic material between two individuals with the appearance of recombinant individuals with an altered genotype.

Reaction mechanisms.

1. Conjugation – exchange of genetic information through direct contact between the donor and recipient.

2. Fusion of protoplasts - exchange of genetic information during direct contact of sections of the cytoplasmic membrane in bacteria lacking a cell wall.

3. Transformation – transfer of genetic information in the form of isolated DNA fragments when the recipient cell is in an environment containing donor DNA.

4. Transduction is the transfer of genetic information between bacterial cells using temperate transducing phages. It can be specific and non-specific.

9. Bacteriophages

Phage virions consist of a head containing the viral nucleic acid and a tail.

The nucleocapsid of the phage head has a cubic type of symmetry, and the process has a helical type, i.e., bacteriophages have a mixed type of symmetry.

Phages can exist in two forms:

1) intracellular (this is a prophage, pure DNA);

2) extracellular (this is a virion).

There are two types of phage-cell interaction.

1. Lytic (productive viral infection). This is a type of interaction in which virus reproduction occurs in a bacterial cell. She dies in the process. First, phages are adsorbed on the cell wall. Then comes the penetration phase. At the site of phage adsorption, lysozyme acts, and due to the contractile proteins of the tail part, the phage nucleic acid is injected into the cell. This is followed by a middle period, during which the synthesis of cellular components is suppressed and the disjunctive mode of phage reproduction occurs. In this case, the phage nucleic acid is synthesized in the nucleoid region, and then protein synthesis occurs on the ribosomes. Phages that have a lytic type of interaction are called virulent.

In the final period, as a result of self-assembly, proteins are folded around the nucleic acid and new phage particles are formed. They leave the cell, breaking its cell wall, i.e., lysis of the bacterium occurs.

2. Lysogenic. These are temperate phages. When a nucleic acid penetrates a cell, it is integrated into the cell's genome, and long-term cohabitation of the phage with the cell is observed without its death. When external conditions change, the phage may leave its integrated form and develop a productive viral infection.

Based on specificity, the following are distinguished:

1) polyvalent phages (lyse cultures of one family or genus of bacteria);

2) monovalent (lyse cultures of only one type of bacteria);

3) typical (capable of causing lysis only of certain types (variants) of a bacterial culture within a bacterial species).

Phages can be used as diagnostic drugs to determine the genus and species of bacteria isolated during bacteriological research. However, they are more often used for the treatment and prevention of certain infectious diseases.

10. Morphology of viruses, types of virus-cell interaction

Viruses are microorganisms that make up the kingdom Vira.

Viruses can exist in two forms: extracellular (virion) and intracellular (virus).

The shape of virions can be: round, rod-shaped, in the form of regular polygons, filamentous, etc.

Their sizes range from 15–18 to 300–400 nm.

In the center of the virion is a viral nucleic acid, covered with a protein shell - a capsid, which has a strictly ordered structure. The capsid shell is made up of capsomeres.

Nucleic acid and the capsid shell make up the nucleocapsid.

The nucleocapsid of complexly organized virions is covered with an outer shell - a supercapsid.

DNA can be:

1) double-stranded;

2) single-chain;

3) ring;

4) double-stranded, but with one shorter chain;

5) double-chain, but with one continuous and the other fragmented chains.

RNA can be:

1) single thread;

2) linear double-stranded;

3) linear fragmented;

4) ring;

Viral proteins are divided into:

1) genomic – nucleoproteins. Provide replication of viral nucleic acids and viral reproduction processes;

2) capsid shell proteins are simple proteins with the ability to self-assemble. They form geometric structures in which several types of symmetry are distinguished: spiral, cubic or mixed;

3) supercapsid shell proteins are complex proteins. Perform protective and receptor functions.

Among the proteins of the supercapsid shell are:

a) anchor proteins (ensure contact of the virion with the cell);

b) enzymes (can destroy membranes);

c) hemagglutinins (cause hemagglutination);

d) elements of the host cell.

Interaction of viruses with the host cell

There are four types of interaction:

1) productive viral infection (virus reproduction occurs and cells die);

2) abortive viral infection (virus reproduction does not occur, and the cell restores the impaired function);

3) latent viral infection (the virus reproduces, but the cell retains its functional activity);

4) virus-induced transformation (a cell infected with a virus acquires new properties).

11. Cultivation of viruses. Antiviral immunity

Basic methods of cultivating viruses:

1) biological – infection of laboratory animals. When infected with the virus, the animal becomes ill;

2) cultivation of viruses in developing chicken embryos. Chicken embryos are grown in an incubator for 7-10 days and then used for cultivation.

As a result of infection, the following may occur and appear:

1) death of the embryo;

2) developmental defects;

3) accumulation of viruses in allantoic fluid;

4) reproduction in tissue culture.

The following types of tissue cultures are distinguished:

1) transplantable – tumor cell cultures; have high mitotic activity;

2) primary trypsinized - subjected to primary trypsin treatment; this treatment disrupts intercellular communication, resulting in the isolation of individual cells.

Special media are used to maintain tissue culture cells. These are liquid nutrient media of complex composition containing amino acids, carbohydrates, growth factors, protein sources, antibiotics and indicators for assessing the development of tissue culture cells.

The reproduction of viruses in tissue culture is judged by their cytopathic effect.

The main manifestations of the cytopathic effect of viruses:

1) virus replication may be accompanied by cell death or morphological changes in them;

2) some viruses cause cell fusion and the formation of multinuclear syncytium;

3) cells can grow but not divide, resulting in the formation of giant cells;

4) inclusions appear in the cells (nuclear, cytoplasmic, mixed). Inclusions may appear pink (eosinophilic inclusions) or blue (basophilic inclusions);

5) if viruses that have hemagglutinins multiply in tissue culture, then during the process of reproduction the cell acquires the ability to adsorb red blood cells (hemadsorption).

Features of antiviral immunity

Antiviral immunity begins with the stage of presentation of the viral antigen by T helper cells.

Immunity is aimed at neutralizing and removing the virus, its antigens and virus-infected cells from the body. There are two main forms of participation of antibodies in the development of antiviral immunity:

1) neutralization of the virus with antibodies;

2) immune lysis of virus-infected cells with the participation of antibodies.

12. General characteristics of the form and periods of infection

Infection– this is a set of biological reactions with which a macroorganism responds to the introduction of a pathogen.

For an infectious disease to occur, a combination of the following factors is necessary:

1) the presence of a microbial agent;

2) susceptibility of the macroorganism;

3) the presence of an environment in which this interaction occurs.

Microbial agents are pathogenic and opportunistic microorganisms.

An epidemic is a widespread infection in a population covering large areas.

A pandemic is the spread of an infection to almost the entire territory of the globe.

Endemic diseases (with natural focality) are diseases for which territorial areas with an increased incidence of this infection are noted.

Classification of infections

1. By etiology: bacterial, viral, protozoal, mycoses, mixed infections.

2. By the number of pathogens: monoinfections, polyinfections.

3. According to severity: mild, severe, moderate.

4. By duration: acute, subacute, chronic, latent.

5. By transmission routes:

1) horizontal:

a) airborne droplets;

b) fecal-oral;

c) contact;

d) transmission;

e) sexual;

2) vertical:

a) from mother to fetus (transplacental);

b) from mother to newborn during the birth act;

3) artificial (artificial).

Depending on the location of the pathogen, there are:

1) focal infection;

2) generalized infection. The most severe form is sepsis.

The following periods of infectious diseases are distinguished:

1) incubation; from the moment the pathogen enters the body until the first signs of the disease appear;

2) prodromal; characterized by the appearance of the first unclear general symptoms. The pathogen multiplies intensively, colonizes tissue, and begins to produce enzymes and toxins. Duration – from several hours to several days;

3) the height of the disease; characterized by the appearance of specific symptoms;

a) death;

b) recovery (clinical and microbiological). Clinical recovery: the symptoms of the disease have faded, but the pathogen is still in the body. Microbiological – complete recovery;

c) chronic carriage.

13. Infectious agents and their properties

Among the bacteria, according to their ability to cause disease, the following are distinguished:

1) pathogenic species have the potential to cause an infectious disease;

Pathogenicity is the ability of microorganisms, entering the body, to cause pathological changes in its tissues and organs. This is a qualitative species characteristic.

2) opportunistic bacteria can cause an infectious disease when the body’s defenses are reduced;

Pathogenicity is realized through virulence - this is the ability of a microorganism to penetrate a macroorganism, multiply in it and suppress its protective properties.

This is a strain trait and can be quantified. Virulence is a phenotypic manifestation of pathogenicity.

Quantitative characteristics of virulence are:

1) DLM (minimum lethal dose) is the number of bacteria, when introduced into the body of laboratory animals, 95–98% of the death of animals in the experiment occurs;

2) LD 50 is the amount of bacteria that causes the death of 50% of the animals in the experiment;

3) DCL (lethal dose) causes 100% death of animals in the experiment.

Virulence factors include:

1) adhesion - the ability of bacteria to attach to epithelial cells;

2) colonization - the ability to multiply on the surface of cells, which leads to the accumulation of bacteria;

3) penetration – the ability to penetrate cells;

4) invasion - the ability to penetrate into the underlying tissue. This ability is associated with the production of enzymes such as hyaluronidase and neuraminidase;

5) aggression – the ability to resist factors of nonspecific and immune defense of the body.

Factors of aggression include:

1) substances of different nature that are part of the surface structures of the cell: capsules, surface proteins, etc. Many of them suppress the migration of leukocytes, preventing phagocytosis;

2) enzymes - proteases, coagulase, fibrinolysin, lecithinase;

3) toxins, which are divided into exo- and endotoxins.

Exotoxins are highly toxic proteins. They are heat labile and are strong antigens to which the body produces antibodies that undergo toxin neutralization reactions. This trait is encoded by plasmids or prophage genes.

Endotoxins are complex complexes of lipopolysaccharide nature. They are thermostable, weak antigens, and have a general toxic effect. Encoded by chromosomal genes.

14. Normal human microflora

Normal human microflora is a collection of many microbiocenoses, characterized by certain relationships and habitat.

Types of normal microflora:

1) resident – ​​permanent, characteristic of a given species;

2) transient - temporarily introduced, uncharacteristic for a given biotope; it does not actively reproduce.

Factors influencing the state of normal microflora.

1. Endogenous:

1) secretory function of the body;

2) hormonal levels;

3) acid-base state.

2. Exogenous living conditions (climatic, household, environmental).

In the human body, blood, cerebrospinal fluid, joint fluid, pleural fluid, thoracic duct lymph, internal organs: heart, brain, parenchyma of the liver, kidneys, spleen, uterus, bladder, lung alveoli are sterile.

Normal microflora lines the mucous membranes in the form of a biofilm. This framework consists of polysaccharides of microbial cells and mucin. Biofilm thickness is 0.1–0.5 mm. It contains from several hundred to several thousand microcolonies.

Stages of formation of normal microflora of the gastrointestinal tract (GIT):

1) accidental contamination of the mucous membrane. Lactobacilli, clostridia, bifidobacteria, micrococci, staphylococci, enterococci, E. coli, etc. enter the gastrointestinal tract;

2) formation of a network of tape bacteria on the surface of the villi. Mostly rod-shaped bacteria are fixed on it, and the process of biofilm formation is constantly underway.

Normal microflora is considered as an independent extracorporeal organ with a specific anatomical structure and functions.

Functions of normal microflora:

1) participation in all types of exchange;

2) detoxification in relation to exo- and endoproducts, transformation and release of medicinal substances;

3) participation in the synthesis of vitamins (groups B, E, H, K);

4) protection:

a) antagonistic (associated with the production of bacteriocins);

b) colonization resistance of mucous membranes;

5) immunogenic function.

The highest contamination rates are characterized by:

1) large intestine;

2) oral cavity;

3) urinary system;

4) upper respiratory tract;

45. Pathogens of ARVI

Parainfluenza virus and RS virus belong to the family Paramyxoviridae.

These are spherical viruses with a spiral type of symmetry. The average virion size is 100–800 nm. They have a supercapsid shell with spinous processes. The genome is represented by a linear, non-segmented RNA molecule. The RNA is associated with a major protein (NP).

The shell contains three glycoproteins:

1) HN, which has hemagglutinating and neuraminidase activity;

2) F, responsible for fusion and exhibiting hemolytic and cytotoxic activity;

3) M protein.

Virus replication is completely realized in the cytoplasm of host cells. The human parainfluenza virus belongs to the genus Paramyxovirus. Viruses are characterized by the presence of their own RNA-dependent RNA polymerase (transcriptase).

Based on the differences in the antigenic structure of the HN, F and NP proteins of human parainfluenza viruses, four main serotypes are distinguished.

The pathogen reproduces in the epithelium of the upper respiratory tract, from where it enters the bloodstream.

Clinical manifestations in adults most often occur in the form of catarrh of the upper respiratory tract. In children, the clinical picture is more severe.

The main route of transmission of the parainfluenza virus is airborne. The source of infection is the patient (or virus carrier).

Laboratory diagnostics:

1) rapid diagnostics (ELISA);

2) isolation of the pathogen in monolayers of human or monkey embryonic kidney cultures;

3) serodiagnosis (RSK, RN, RTGA with paired sera).

PC virus is the main causative agent of lower respiratory tract diseases in newborns and young children. Belongs to the genus Pneumovirus.

Characterized by low stability, virions are prone to self-disintegration.

The pathogen replicates in the epithelium of the airways, causing the death of infected cells, and exhibits pronounced immunosuppressive properties.

PC virus causes annual epidemic respiratory tract infections in newborns and young children; Adults can be infected, but their infection is mild or asymptomatic. The main route of transmission is airborne droplets.

After recovery, unstable immunity is formed.

Laboratory diagnostics:

1) express diagnostics - determination of virus antigens in nasal discharge using ELISA;

2) specific antigens are detected in RSC and RN.

Causal therapy has not been developed.