Normal microflora of humans and animals. Biological role, ways of studying

less frequently isolated from a healthy body.

An animal's body normally contains hundreds of species of microorganisms; Bacteria predominate among them. Viruses and protozoa are represented by a much smaller number of species. It is often impossible to draw a clear boundary between saprophytes and pathogenic microbes that are part of the normal microflora. The blood and internal organs of animals are practically sterile. Do not contain microbes and some cavities in contact with the external environment - the uterus, bladder. Microbes in the lungs are quickly destroyed. But in oral cavity, in the nose, in the intestines, in the vagina there is a constant normal microflora characteristic of each area of ​​​​the body (autochthonous). During the intrauterine period, the organism develops in the sterile conditions of the uterine cavity, and its primary seeding occurs when passing through the birth canal and on the first day upon contact with the environment. Then, for a number of years after birth, a microbial “landscape” characteristic of certain biotopes of his body is formed. Among the normal microflora, there are resident (permanent) obligate microflora and transient (non-permanent) microflora, which is not capable of long-term existence in the body.

The totality of microorganisms that have adapted to life in the human and animal body and do not cause any disturbances in the physiological functions of the macroorganism is called normal microflora.

The normal microflora of humans and animals is divided into obligate and optional. The obligate microflora includes relatively permanent saprophytic and opportunistic microorganisms that are maximally adapted to exist in the host organism. Facultative microflora is random and temporary. It is determined by the entry of microorganisms from environment, as well as the state of the immune system of the macroorganism.

Permanent inhabitants of the oral cavity are streptococci, lactobacilli, corynebacteria, bacteroids, as well as yeast fungi, actinomycetes, mycoplasmas and protozoa. Facultative inhabitants include Enterobacteria, spore-forming bacteria and Pseudomonas aeruginosa. Availability Escherichia coli is an indicator of the unfavorable condition of the oral cavity.

a major role in maintaining the quality and quantitative composition microorganisms in the oral cavity is played by saliva containing various enzymes with antibacterial activity.

Microorganisms are almost absent in the human stomach. Sometimes found in small amounts in the stomach Sarcina ventriculi, Bacillus subtilis and some yeast.

Relatively few bacteria live in the small intestine (10 2 -10 3), mainly aerobic forms. But in the large intestine there is a colossal number of microbes, including more than 260 different types of facultative and obligate anaerobes. The main inhabitants of the large intestine are bacteroids, bifidobacteria, fecal streptococcus, E. coli, lactic acid bacteria. The latter in the intestine act as antagonists of putrefactive microflora and some pathogenic microbes.

A lot of microbes come from the surrounding air. Most of the microorganisms linger in the upper respiratory tract. The bronchi and alveoli of the lungs are practically sterile. The microflora of the upper respiratory tract contains relatively constant microbes, represented by staphylococci, corynebacteria, streptococci, bacteroids, capsular gram-negative bacteria, etc. In addition to bacteria in the upper respiratory tract, some viruses, in particular, adenoviruses, can remain in a latent state for a long time.

The substrate for feeding bacteria on the surface of the skin is the secretions of sweat and sebaceous glands, as well as dying epithelial cells. The skin of open parts of the body - hands, face, neck - is richest in microorganisms. The vast majority of skin microorganisms are represented by saprophytic bacteria - staphylococci, bacilli, mycobacteria, corynebacteria and yeast fungi, and only 5% of the analyzes highlight the opportunistic microbe - Staphylococcus aureus. In sanitary and bacteriological analyzes, the detection of Escherichia coli on the surface of the skin indicates contamination with feces.

Normal microflora in humans and animals plays an important role in the formation of natural immunity. Obligate microorganisms producing substances such as antibiotics, lactic acid, alcohols, hydrogen peroxide and other compounds have pronounced antagonistic properties against many pathogenic bacteria. Qualitative and quantitative disturbances in the composition of the microbial flora in the human body are called dysbacteriosis. Dysbacteriosis occurs most often as a result of prolonged use of antibiotics, as well as chronic infections, radiation and the action of extreme factors. The development of dysbacteriosis is explained by the suppression of the obligate microflora of the macroorganism.

Questions for self-control:

1. How does temperature affect the vital activity of microorganisms? Describe psychrophiles, mesophylls and thermophiles.

2. Explain the effect of hydrostatic and osmotic pressure on microorganisms.

3. How do osmophilic microorganisms differ from halophilic ones? Give examples of these groups of microorganisms.

4. What is the importance of water for microorganisms?

5. Explain the mechanism of action on microorganisms of different types of irradiation. What rays have a bactericidal effect?

6. What physical factors are used in practice to combat microorganisms?

7. What groups are microorganisms divided into in relation to molecular oxygen?

8. Give examples of different sensitivity of microorganisms to the pH of the medium. What is the reason for this?

9. What chemical substances called antimicrobial? Give examples of their practical application.

10. Explain the division of normal human microflora into obligate and facultative. Give examples of each group.

Normal microflora of humans and animals necessary condition maintaining the health of the macroorganism. Violation of microbial biocenoses in different organs and systems of the body leads to the development of pathological processes, a decrease in the activity of the body's defenses, and the development of dysbacteriosis. If a newborn is raised in sterile conditions, fed with sterile food, i.e. deprive him of normal microflora, he will develop poorly, lag behind in growth and may die.

Many of the microorganisms that live in the human or animal body represent the normal microflora and are non-pathogenic or conditionally pathogenic in terms of pathogenicity. Representatives of saprophytic and conditionally pathogenic microflora living in the body of a person or animal have been studied less in the past, since this microflora was considered harmless to the macroorganism and the main attention was directed to representatives of pathogenic microflora.

At present, the importance of non-pathogenic microbes in the occurrence and development of diseases in humans has increased to a problem that can hardly be overestimated.

Saprophytic and conditionally pathogenic microbes that are in the body, or penetrated from the environment, under certain conditions against the background of infection, beriberi, constant physical and mental overwork, hypothermia, stressful situations, radiation exposure, protein depletion and other factors can cause both in humans , and in animals can cause infectious diseases, which often end in death. The resident microflora of the oral cavity can play a significant role in diseases of infectious origin (for example, with agranulocytosis), while bacteroids, fusiform bacteria, streptococci, Ps.aeruginosa, C.albicans, St.aueus, E.cjli are found.

Microorganisms such as E.coli, Kl.pneumoniae, Pr.vulgaris, Cl.perfringens, St.aureus, which are part of the normal intestinal microflora, can cause the development of inflammatory processes, and often abscesses. Representatives of the resident microflora can become causative agents of bacteremia and sepsis. Saprophytic and conditionally pathogenic microorganisms can cause the development of bacterial shock, which develops as a result of the simultaneous entry into the blood of a significant amount of microbial individuals and their toxins, or even only microbial toxins. Bacterial shock occurs after a sudden onset of mass bacteremia due to chronic focal infection that has overcome protective barriers, surgical intervention against the backdrop of a septic focus. Very often, bacterial shock develops during manipulations of the genitourinary system during the period of infection, during transfusion of blood contaminated with microbes, with prolonged intravenous infusions of drugs and nutrients that carry bacteria into the blood. The most common pathogens of bacterial shock are E.coli, Ps.aeruginosa, Proteus vulgaris, St.epidermidis, St.aureus, Kl. Pneumoniae, representatives of the genus Bacteroides, Cl.perfringens, hemolytic streptococcus, meningococcus, pneumococcus.

The most severe bacterial shock occurs with an infection caused by Pseudomonas, Proteus, Escherichia. When the body is weakened (hypothermia, injuries, exhaustion, etc.), microorganisms that are permanent residents of the upper respiratory tract can cause various diseases (bronchitis, pneumonia, etc.), while affecting the lower respiratory tract. The resident microflora of the urogenital organs, which includes St.aureus, St.epidermidis, E.coli, Klebsiella sp., Cl.perfringens, candida, diphtheroids, vibrios, bacteroids, mycoplasmas and other microorganisms, can cause the development of vulvitis, urethritis, disease uterus, prostate, appendages. AT recent decades in hospitals of medical institutions, the number of patients in whom representatives of the resident microflora, conditionally pathogenic microorganism often call for severe purulent-inflammatory processes, has significantly increased. In recent years, the number of patients with purulent-inflammatory processes in the maxillofacial region has significantly increased, especially in individuals with reduced activity of natural defense factors.

Among enteropathogenic serotypes of Escherichia coli, causative agents of gastrointestinal diseases in young cattle were identified.

Yeast-like fungi of the genus Candida are widespread in nature and are permanent inhabitants of the outer integument, mucous membranes and gastrointestinal tract of both humans and animals. The etiological role of Candida albikans, C.tropicalis in the occurrence of abortions in cows, rabbits, cats, mice, guinea pigs. In the study of histological preparations of the affected organs (kidneys, spleen, lungs, liver), not only yeast-like, but also mycelial forms of the fungus germinating in the tissues are found. This indicates the active development of the fungus in the body. Pathogenic spirochetes in adult pigs cause leptospirosis, and pathogenic E. coli in piglets cause coli - bacteriosis. Often infections in animals are caused by viruses. People, in direct contact with sick animals or with various substrates contaminated with microbes secreted from these animals, become infected and fall ill.

The most dangerous anthropozoonotic infections are anthrax, glanders, brucellosis, tuberculosis, plague, trypanosomiasis, rabies and many others.

Research conducted by scientists on all continents over many decades has made it possible to understand the role of microorganisms not only in the circulation of substances, but also in the occurrence of infectious diseases in humans, animals and plants. For millions of years, macro- and micro-organisms have mutually adapted and become necessary to each other. Microbes - normal inhabitants of an animal or plant organism have become integral companions of the macroorganism and play a significant role in their life.

Pseudomonas aeruginosa is a Gram-negative, rod-shaped bacterium that is an obligatory aerobe. The dimensions of this microorganism in thickness reach up to 0.8 microns, and in length up to 3 microns. The most mobile pathogenic microorganism that lives in aquatic environment. Able to stay and successfully multiply in a humid atmosphere and in water for a long time. The temperature that is suitable for the development of this microorganism is 37 degrees. For humans, this microorganism is conditionally pathogenic, since it never affects healthy tissues.

Hepatitis E - was first studied and described in 1983. It is a microorganism in the form of a sphere with an RNA helix. Hepatitis E is transmitted mainly through dirty water, by the fecal-oral route. Hepatitis E disease is seasonal and is especially aggravated in the autumn-winter period.

Aeromonas spp. - belongs to the family of gram-negative bacteria that are rod-shaped, capable of growing both in an oxygen-free environment and in an oxygen environment. When infected with this pathogen, acute infections of two types occur: cholera-like, which is accompanied by watery diarrhea; an infection similar to dysentery, which is accompanied by bloody stools. Infection occurs through contaminated water, but is sometimes transmitted through food. A person can become infected only when he has open wounds.

Shigella or Shigella are aerobic gram-negative non-motile bacteria expressed in the form of a rod. They can cause intestinal infections in humans. The common name for this disease is dysentery. It is transmitted through contaminated water, dirty food and dirty household items.

Vibrio cholerae, in translation - cholera vibrio. Gram-negative rod, small in size, comma-shaped. It can develop perfectly at temperatures from 30 to 40 degrees Celsius. They cause a disease called cholera. You can get infected very easily through ordinary drinking water, which got this bacterium. When bathing in polluted water bodies and swallowing this water, the likelihood of infection is also high.

Yersinia enterocolitica are gram-negative bacteria that do not form spores. They are anaerobes. Resistant to environmental influences and can be stored for a long time. Infection with this bacterium causes an acute disease called yersiniosis in humans. They damage the gastrointestinal tract and lead to intoxication of the body, as a result, the musculoskeletal system or liver can be affected.

Enteroviruses are small, hexahedral-shaped viruses that do not have a membrane shell, contain a single helix of RNA, and live for a long time in waste and chlorinated water. The most serious disease that enteroviruses can cause in humans is poliomyelitis.

Salmonella, or salmonella, are Gram-negative motile aerobes. They cause an infectious disease called salmonellosis.

Adenoviruses - today there are about 100 types of such viruses, 49 of which can cause disease in humans. They mainly affect the respiratory system, eyes and lymph nodes. Less often affects the intestines and bladder.

44. Phenotypic and genotypic variation prokaryotes. The meaning of mutations. Prospects for genetic engineering.

General concepts.

Heredity- the ability of living organisms to maintain certain characteristics for many generations. Variability- the acquisition of new features that distinguish them from other generations under the influence of environmental factors. The science that studies heredity and variation is called genetics.

Phenotype- the general complex of morphological and physiological properties of each individual, and serves as an external manifestation of the genotype.

Genotype is the total amount of genes that a cell possesses. It defines a whole group of properties of an organism that are specific to a given species.

Normal microflora of the animal organism. The body represents a whole world for microorganisms with many ecological niches. Under natural conditions, the body of any animal is inhabited by many microorganisms. Among them there may be random forms, but for many species the body of the animal is the main or only habitat. The nature and mechanisms of interactions of a macroorganism with microorganisms are diverse and play a decisive role in the life and evolution of many species of the latter. For an animal, microorganisms also represent an important environmental factor which determines many aspects of its evolutionary changes.

FROM modern positions normal microflora is considered as a set of microbiocenoses occupying numerous ecological niches on the skin and mucous membranes of all body cavities communicating with the external environment. In a significant part, the microflora is the same in all animals in the compared biotopes, but there are individual differences in the composition of the microbiocenosis. The automicroflora of a healthy animal remains constant and is maintained by homeostasis; tissues and organs that do not communicate with the external environment are sterile. The organism and its normal microflora constitute a single ecological system: the microflora serves as a kind of "extracorporeal organ" that plays an important role in the life of the animal. Being a biological factor of protection, the normal microflora is the barrier, after the breakthrough of which the inclusion of non-specific defense mechanisms is induced. If the factors that act directly and indirectly on colonization resistance and the functioning of normal microflora, in their intensity and duration, exceed the compensatory capabilities of the microorganism as an ecosystem, then microecological disturbances will inevitably occur. The severity and duration of these disorders will depend on the dose and duration of exposure.

Skin microflora. The skin has its own characteristics, its own relief, its own "geography". The cells of the epidermis are constantly dying off, and the plates of the stratum corneum are sloughed off. The surface of the skin is constantly "fertilized" by the products of the secretion of the sebaceous and sweat glands. Sweat glands provide microorganisms with salts and organic compounds, including nitrogen-containing ones. The secretions of the sebaceous glands are rich in fats.

Microorganisms inhabit mainly areas of the skin covered with hair and moistened with sweat. In such areas, there are about 1.5 x 10 6 cells/cm 2 . Some types of microorganisms are confined to strictly defined zones.

As a rule, gram-positive bacteria predominate on the skin. Typical inhabitants are various species of Staphylococcus, in particular S. epidermidis, Micrococcus, Propionibacterium, Corynebacterium, Brevibacterium, Acinetobacter.

The appearance of S. aureus indicates adverse changes in the microflora of the body. Representatives of the genus Corynebacterium sometimes account for up to 70% of the entire skin microflora. Some species are lipophilic, that is, they form lipases that destroy the secretions of the sebaceous glands.

Most microorganisms that inhabit the skin do not pose any danger to the host, but some, and primarily S. aureus, are opportunistic pathogens.

Disruption of the normal bacterial community of the skin can have adverse effects on the host.

On the skin, microorganisms are subject to the action of bactericidal factors of sebaceous secretion, which increase acidity (accordingly, the pH value decreases). Predominantly S. epidermidis, micrococci, sarcins, aerobic and anaerobic diphtheroids live in such conditions. Other types -

S. aureus, a-hemolytic and non-hemolytic streptococci - it is more correct to consider them transient. The main areas of colonization are the epidermis (especially the stratum corneum), skin glands(sebaceous and sweat) and upper sections of hair follicles. The microflora of the hairline is identical to the microflora of the skin.

Microflora of the gastrointestinal tract. The most active microorganisms populate the gastrointestinal tract due to the abundance and diversity of nutrients in it.

The acidic environment of the stomach is the initial factor controlling the reproduction of microorganisms entering it with food. After passing through the gastric barrier, microbes enter more favorable conditions and multiply in the intestines with sufficient nutrients and an appropriate temperature. The vast majority of microorganisms live in the form of fixed microcolonies and lead a predominantly immobilized lifestyle, located on the mucous membrane in layers. The first layer is directly on the epithelial cells (mucosal microflora), the subsequent layers (one above the other) are translucent microflora immersed in a special mucous substance, which is partly a product of the intestinal mucosa, partly a product of the bacteria themselves.

Having attached, the microorganisms produce an exapolis-charide glycocalyx, which envelops the microbial cell and forms a biofilm, within which bacteria divide and intercellular interaction takes place. The microflora of the large intestine is divided into M-flora (mucosal) and P-flora (cavity), which lives in the intestinal lumen. M-flora is a parietal flora, the representatives of which are either fixed on the receptors of the intestinal mucosa (bifidum-flora) or indirectly, through interaction with other microorganisms, are attached to bifidobacteria.

Adhesion is carried out through the surface structures of bacteria containing glycolipids (lectins), which are complementary to receptors (glycoproteins) of epithelial cell membranes. Lectins can be localized in bacterial membranes, on their surface, as well as on specific fimbriae, which, passing through the thickness of the exopolysaccharide glycocalyx, fix the bacteria to the corresponding mucosal epithelial receptors.

Thus, a biofilm is formed on the surface of the intestinal mucosa, consisting of exopolysaccharide mucin of microbial origin and billions of microcolonies. The thickness of a biofilm varies from fractions to tens of micrometers, while the number of microcolonies can reach several hundred and even thousands along the layer height. As part of a biofilm, microorganisms are tens or even hundreds of times more resistant to adverse factors than when they are in a free-floating state, i.e., M-flora is more stable. Mainly, these are bifidobacteria and lactobacilli, which form a layer of the so-called bacterial turf, which prevents the penetration of the mucous membrane by pathogenic and opportunistic microorganisms. Competing for interaction with epithelial cell receptors, M-flora causes colonization resistance of the colon. P-flora, along with bifido-to lactobacilli, includes other permanent inhabitants of the intestine.

Obligate microflora(resident, indigenous, autochthonous) is normally found in all healthy animals. These are microorganisms that are maximally adapted to existence in the intestines. Up to 95% is accounted for by the anaerobic flora (bacteroids, bifidobacteria, lactobacilli) - this is the main microflora (10 9 ... 10 yu of microbial bodies in 1 g).

Facultative microflora found in some of the subjects. From 1 to 4% of the total number of microorganisms are facultative anaerobes (enterococci, Escherichia coli) - this is the accompanying flora (10 5 ... 10 7 microbial bodies in 1 g).

Transient microflora(temporary, optional) occurs in some animals (at certain intervals). Its presence is determined by the intake of microbes from the environment and the state of the immune system. It consists of saprophytes and conditionally pathogenic microorganisms (Proteus, Klebsiella, Pseudomonas aeruginosa, fungi of the genus Candida) - this is the residual flora (up to 10 4 microbial bodies per 1 g).

Enters the intestines of herbivores a large number of fiber. Only a few invertebrates are known to be able to digest fiber on their own. In most cases, the digestion of cellulose occurs due to its destruction by bacteria, and the animal consumes the products of its degradation and the cells of microorganisms as food. Thus, there is cooperation, or symbiosis. This type of interaction has reached the greatest perfection in ruminants. In their rumen, the food lingers long enough for the components of plant fibers available to microorganisms to be destroyed. In this case, however, the bacteria use a significant portion of the plant protein, which in principle could be broken down and used by the animal itself. In many animals, the interaction with the intestinal microflora is intermediate. For example, in the intestines of horses, rabbits, mice, feed is largely used up before the rapid development of bacteria begins. But it should be noted that, unlike predators, in such animals, food lingers longer in the intestines, which contributes to its fermentation by bacteria.

The most active vital activity of microorganisms is observed in the large intestine. Anaerobes develop by carrying out fermentation, during which organic acids are formed - mainly acetic, propionic and butyric. With a limited intake of carbohydrates, the formation of these acids is energetically more favorable than the production of ethanol and lactic acid. The destruction of proteins that occurs here leads to a decrease in the acidity of the medium. The accumulated acids can be used by the animal.

The composition of the intestinal microflora of various animals includes a number of types of bacteria that can destroy cellulose, hemicelluloses, and pectins. In many mammals, members of the genera Bacteroides and Ruminococcus live in the intestines; V. succinogenes was found in the intestines of horses, cows, sheep, antelopes, rats, monkeys; R. album and R. flavefaciens, actively destroying fiber, live in the intestines of horses, cows, and rabbits. Other fiber-fermenting intestinal bacteria include Butyrivibrio fibrisolvens and Eubacterium cellulosolvens. The genera Bacteroides and Eubacterium are represented in the intestines of mammals by a number of species, some of which also degrade protein substrates.

The rumen of ruminants is abundantly populated a large number types of bacteria and protozoa. The anatomical structure and conditions in the rumen are almost ideal for the life of microorganisms. On average, according to various authors, the number of bacteria is 10 9 ... 10 10 cells per 1 g of cicatricial contents.

In addition to bacteria, the breakdown of feed nutrients and the synthesis of organic compounds important for the animal organism in the rumen are also carried out by various types of yeast, actinomycetes, and protozoa. The number of ciliates in 1 ml of content can reach 3-4 million.

Over time, the species composition of cicatricial microorganisms undergoes changes.

During the milk period, lactobacilli and certain types of proteolytic bacteria predominate in the rumen of calves. The complete formation of the cicatricial microflora is completed when the animals switch to feeding on roughage. According to some authors, in adult ruminants, the species composition of the cicatricial microflora is constant and does not change significantly depending on feeding, season, and a number of other factors. Functionally, the most importance represent the following types of bacteria: Bacteroides succinogenes, Butyrivibrio

fibrisolvens, Ruminococcus flavefaciens, Ruminococcus album, Eubacterium cellulosolvens, Clostridium cellobioparum, Clostridium locheadi, etc.

The main fermentation products of fiber and other carbohydrates are butyric acid, carbon dioxide and hydrogen. Ruminal bacteria of many species (Bacteroides amylophilus, Bacteroides ruminicola, etc.) take part in the conversion of starch, including cellulolytic bacteria, as well as certain types of ciliates.

The main fermentation products are acetic acid, succinic acid, formic acid, carbon dioxide and in some cases hydrogen sulfide.

The content of the rumen contains a wide variety of bacterial species that utilize various monosaccharides (glucose, fructose, xylose, etc.) supplied with food, and mainly formed during the hydrolysis of polysaccharides. In addition to those described above, which have enzymes that destroy polysaccharides and disaccharides, there are many types of bacteria in the rumen of ruminants that preferentially use monosaccharides, mainly glucose. These include: Lachnospira multiparus, Selenomonas ruminantium, Lactobacillus acidophilus. Bifidobacterium bifidum, Bacteroides coa-gulans, Lactobacillus fermentum, etc.

It is now known that protein in the rumen is cleaved by proteolytic enzymes of microorganisms to form peptides and amino acids, which, in turn, are exposed to deaminases, resulting in the formation of ammonia. Deaminating properties are possessed by cultures belonging to the species: Selenomonas ruminantium, Megasphaera elsdenii, Bacteroides ruminicola, etc.

Most of the vegetable protein consumed with feed is converted in the rumen into microbial protein. As a rule, the processes of splitting and protein synthesis proceed simultaneously. A significant part of rumen bacteria, being heterotrophs, uses inorganic nitrogen compounds for protein synthesis. The most functionally important cicatricial microorganisms (Bacteroides ruminicola, Bacteroides succinogenes, Bacteroides amylophilus, etc.) use ammonia for the synthesis of nitrogenous substances in their cells.

A number of types of scar microorganisms (Streptococcus bovis, Bacteroides succinogenes, Ruminococcus flavefaciens, etc.) use sulfides to build sulfur-containing amino acids in the presence of cystine, methionine or homocysteine ​​in the medium.

The small intestine contains a relatively small number of microorganisms. Most often, bile-resistant enterococci, Escherichia coli, acidophilic and spore bacteria, actinomycetes, yeast, etc. live there.

The large intestine is the richest in microorganisms. Its main inhabitants are enterobacteria, enterococci, thermophiles, acidophiles, spore bacteria, actinomycetes, yeasts, molds, a large number of putrefactive and some pathogenic anaerobes (Clostridium sporogenes, C. putrificus, C. reg-fringens, C. tetani, Fusobacterium necrophorum). 1 g of herbivore excrement can contain up to 3.5 billion different microorganisms. The microbial mass is about 40% of the dry matter of faeces.

In the large intestine, complex microbiological processes occur associated with the breakdown of fiber, pectin, and starch. The microflora of the gastrointestinal tract is usually divided into obligate (lactic acid bacteria,

E. coli, enterococci, C. perfringens, C. sporogenes, etc.), which adapted to the conditions of this environment and became its permanent inhabitant, and optional, which varies depending on the type of food and water.

The microflora of the respiratory organs. The upper respiratory tract carries a high microbial load - they are anatomically adapted to the deposition of bacteria from the inhaled air. In addition to the usual non-hemolytic and viridescent streptococci, non-pathogenic Neisseria, staphylococci and enterobacteria, meningococci, pyogenic streptococci and pneumococci can be found in the nasopharynx. The upper respiratory tract in newborns is usually sterile and colonized within 2-3 days.

Research recent years showed that saprophytic microflora is most often isolated from the respiratory tract of clinically healthy animals: S. saprophiticus, bacteria of the genera Micrococcus, Bacillus, coryneform bacteria, non-hemolytic streptococci, gram-negative cocci.

In addition, pathogenic and opportunistic microorganisms have been isolated: a- and P-hemolytic streptococci, staphylococci (S. aureus, S. hycus), enterobacteria (escherichia, salmonella, proteus, etc.), pasteurella, P. aeruginosa and in single cases of fungi of the genus Candida.

Saprophytic microorganisms were found more often in the respiratory tract of normally developed animals than poorly developed ones.

The nasal cavity contains the largest number of saprophytes and opportunistic microorganisms. They are represented by streptococci, staphylococci, sardines, pasteurella, enterobacteria, coryneform bacteria, fungi of the genus Candida, Pseudomonos aeruginosa and bacilli. The trachea and bronchi are inhabited by microorganisms of similar groups. Separate groups of f-hemolytic cocci, S. aureus), micrococci, pasteurella, E. soy were found in the lungs.

With a decrease in immunity in animals (especially young animals), the microflora of the respiratory system can cause disease.

Microflora of the urinary tract. Microbial biocenosis of the organs of the genitourinary system is more scarce. The upper urinary tract is usually sterile; in the lower sections, Staphylococcus epidermidis, non-hemolytic streptococci, diphtheroids dominate; fungi of the genera Candida, Toluropsis and Geotrichum are often isolated. The outer sections are dominated by Mycobacterium smegmatis.

The main inhabitant of the vagina is Bacterium vaginale vulgare, which has a pronounced antagonism to other microbes. Normally, in the genitourinary tract, microflora is found only in the external sections (streptococci, lactic acid bacteria).

The uterus, ovaries, testicles, bladder are normally sterile. In a healthy female, the fetus in the uterus is sterile until the onset of labor.

In gynecological diseases, the nature of the microflora changes.

The role of normal microflora. Normal microflora plays an important role in protecting the body from pathogenic microbes, for example by stimulating the immune system, taking part in metabolic reactions. At the same time, this flora can lead to the development of infectious diseases.

Normal microflora competes with pathogenic; the mechanisms of inhibition of the growth of the latter are quite diverse. The main mechanism is selective binding by normal microflora of surface cell receptors, especially epithelial ones. Most representatives of the resident microflora show pronounced antagonism against pathogenic species. These properties are especially pronounced in bifidobacteria and lactobacilli; antibacterial potential is formed by the secretion of acids, alcohols, lysozyme, bacteriocins and other substances. In addition, at a high concentration of these products, the metabolism and release of toxins by pathogenic species (for example, heat-labile toxin by enteropathogenic Escherichia) is inhibited.

Normal microflora is a non-specific stimulant ("irritant") of the immune system; the absence of normal microbial biocenosis causes numerous disorders in the immune system. Another role of microflora was established after gnotobiotes were obtained ( non-microbial animals). Antigens of representatives of normal microflora cause the formation of antibodies in low titers. They are predominantly represented by class A immunoglobulins (IgA), secreted on the surface of the mucous membranes. IgA provides local immunity to penetrating pathogens and prevents commensals from penetrating into deep tissues.

Normal intestinal microflora plays a huge role in the metabolic processes of the body and maintaining their balance.

Providing suction. Metabolism of some substances involves hepatic excretion (as bile) into the intestinal lumen followed by return to the liver; a similar intestinal-hepatic cycle is characteristic of some sex hormones and bile salts. These products are excreted, as a rule, in the form of glucuronides and sulfates, which are not available in this form for reabsorption. Absorption is provided by intestinal bacteria that produce glucuranidase and sulfatase.

exchange of vitamins and minerals. The leading role of normal microflora in providing the body with Her 2+, Ca 2+ ions, vitamins K, E, group B (especially B riboflavin), nicotinic, folic and pantothenic acids is well known. Intestinal bacteria take part in the inactivation of toxic products of endo- and exogenous origin. Acids and gases released during the life of intestinal microbes have a beneficial effect on intestinal motility and its timely emptying.

Thus, the effect of the microflora of the body on the body consists of the following factors.

First, the normal microflora plays an important role in the formation of the body's immunological reactivity. Secondly, representatives of the normal microflora, due to the production of various antibiotic compounds and pronounced antagonistic activity, protect organs that communicate with the external environment from the introduction and unlimited reproduction of pathogenic microorganisms in them. Thirdly, the microflora has a pronounced morphokinetic effect, especially in relation to the mucous membrane of the small intestine, which significantly affects the physiological functions of the digestive canal. Fourth, microbial associations are an essential link in the hepato-intestinal circulation of such important components of bile as bile salts, cholesterol, and bile pigments. Fifth, the microflora in the process of life synthesizes vitamin K and a number of B vitamins, some enzymes and, possibly, other biologically active compounds that are not yet known. Sixthly, the microflora plays the role of an additional enzyme apparatus, breaking down fiber and other indigestible components of the feed.

Violation of the species composition of normal microflora under the influence of infectious and somatic diseases, as well as as a result of prolonged and irrational use of antibiotics leads to a state of dysbacteriosis, which is characterized by a change in the ratio various kinds bacteria, impaired digestibility of digestion products, changes in enzymatic processes, splitting of physiological secrets. To correct dysbacteriosis, the factors that caused this process should be eliminated.

Gnotobiotes and SPF animals. The role of normal microflora in the life of animals, as shown above, is so great that the question arises: is it possible to preserve the physiological state of an animal without microbes. Even L. Pasteur tried to obtain such animals, but the low technical support of such experiments at that time did not allow solving the problem.

At present, not only non-microbial animals (mice, rats, guinea pigs, chickens, piglets, and other species) have been obtained, but a new branch of biology, gnotobiology (from the Greek gnotos - knowledge, bios - life), is also successfully developing. Gnotobiotics lack antigenic “irritation” of the immune system, which leads to underdevelopment of immunocompetent organs (thymus, intestinal lymphoid tissue), deficiency of IgA, a number of vitamins. As a result, physiological functions are disturbed in gnotobiotes: the mass of internal organs decreases, blood volume decreases, and the water content in tissues decreases. Studies using gnotobiotes make it possible to study the role of normal microflora in the mechanisms of infectious pathology and immunity, in the process of synthesis of vitamins and amino acids. By populating the organism of gnotobiotes with certain types (communities) of microorganisms, it is possible to reveal the physiological functions of these species (communities).

SPF-animals are of great value for the development of animal husbandry - they are free only from pathogenic microorganisms and have all the necessary microflora for the implementation of physiological functions. SPF animals grow faster than normal animals, are less likely to get sick, and can serve as the nucleus for disease-free breeding farms. However, to organize such a farm, it is necessary to high level veterinary and sanitary condition.

Dysbacteriosis. The composition of microbial communities in body cavities is influenced by various factors: the quality and quantity of feed, its composition, the animal's motor activity, stress, and much more. The greatest impact is exerted by diseases associated with changes in the physicochemical properties of epithelial surfaces, and the use broad-spectrum antimicrobials that act on any, including non-pathogenic microorganisms. As a result, more resistant species survive - staphylococci, candida and gram-negative rods (enterobacteria, pseudomonads). The consequence of this is qualitative and quantitative changes in microbiocenosis that go beyond the physiological norm, i.e. dysbacteriosis, or dysbiosis. The most severe forms of dysbiosis are staphylococcal sepsis, systemic candidiasis and pseudomembranous colitis; in all forms, damage to the intestinal microflora dominates.

The term "dysbacteriosis" (putrid, or fermentative, dyspepsia) was introduced by A. Nissle in 1916. This is a dynamic violation of the intestinal microecology as a result of a breakdown in adaptation, a change in the protective and compensatory mechanisms that ensure the barrier function of the intestine. Four main groups of factors are involved in maintaining ecological homeostasis:

• 1) immunological specific (immunoglobulins, primarily of the IgA class, which protect the intestinal mucosa from the penetration of allergens of various nature) and non-specific (complement, interferon, lysozyme, transferrin, lactoferrin) humoral protection factors;
• 2) mechanical protection factors (peristaltic movements, epithelium, which is renewed every 6-8 days, macro- and microvilli with a dense network of glycocalyx covering them, ileocecal valve);
• 3) chemical protective factors (saliva, gastric, pancreatic and intestinal juices, bile, fatty acids);
• 4) biological protection factors (normal intestinal microflora).

The problem of dysbacteriosis is relevant and comes to the fore in the pathology of the gastrointestinal tract, allergic diseases, long-term antibiotic therapy.

But dysbacteriosis - it is not a nosological unit, not an independent disease, and a change in the intestinal biocenosis, leading to a violation of the main functions of the microflora and the appearance of clinical symptoms of dysbacteriosis, which does not differ in specificity. The origins of this pathological condition should sometimes be sought at an early age, and the acquired autoflora has such a significant effect on the morphological and physiological status that many characteristics of an adult organism are actually determined by the state of the microflora.

Currently, dysbacteriosis is a manageable pathology not only in terms of treatment, but also in terms of primary prevention.

Correction of dysbiosis. For the correction of dysbacteriosis should be used eubiotics- suspensions of bacteria that can replenish the number of missing or deficient species. In domestic practice, bacterial preparations are widely used in the form of dried live cultures of various bacteria, for example, coli-, lacto- and bifidobacterins (containing E. coli, Lactobacillus and Bifidobacterium species, respectively), bifikol (containing Bifidobacterium and E. coli species), bactisubtil (culture Bacillus subtilis) and others.

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MINISTRY OF AGRICULTURE OF THE RUSSIAN FEDERATION

FGBOU VPO "URAL STATE

AGRARIAN UNIVERSITY»

ESSAY

discipline: "Microbiology of meat"

on the topic "Microflora of the animal body"

Yekaterinburg

FROMcontent

Introduction

1. Definitions, terminology

2. Species composition and quantitative characteristics of the microflora of the most important areas of the animal body

3. Distribution of microorganisms in the gastrointestinal tract

4. Differences in the microflora of the body of different animal species

5. Normal microflora of the body and pathogenic microorganisms

6. Morphofunctional role and metabolic function of the body's automicroflora

Bibliography

ATconducting

The microflora of the organism of mammals, including agricultural, domestic animals and humans, began to be studied along with the development of microbiology as a science, with the advent of the great discoveries of L. Pasteur, R. Koch, I. I. Mechnikov, their students and employees. So, in 1885, T. Escherich isolated from the feces of children an obligatory representative of the intestinal microflora - E. coli, found in almost all mammals, birds, fish, reptiles, amphibians, insects, etc. After 7 years, the first data appeared on the value coli for life, health of the macroorganism. S. O. Jensen (1893) found that different types and strains of Escherichia coli can be both pathogenic for animals (causing septic disease and diarrhea in calves) and non-pathogenic, that is, completely harmless and even beneficial inhabitants of the intestines of animals and person. In 1900, G. Tissier discovered bifibacteria in the feces of newborns and obligatory representatives of the normal intestinal microflora of the body in all periods of its life. Lactic acid sticks (L. acidophilus) were isolated by Moreau in 1900.

1. Odefinitions, terminology

Normal microflora is an open biocenosis of microorganisms found in healthy people and animals (V. G. Petrovskaya, O. P. Marko, 1976). This biocenosis should be characteristic of a completely healthy organism; it is physiological, that is, it helps to maintain the healthy status of the macroorganism, the correct administration of its normal physiological functions. The entire microflora of the animal's body can also be called automicroflora (according to the meaning of the word "auto"), that is, the microflora of any composition (O.V. Chakhava, 1982) given organism in normal and pathological conditions.

The normal microflora, associated only with the healthy status of the body, is divided by a number of authors into two parts:

1. obligate, permanent part, which has developed in phylogeny and ontogenesis in the process of evolution, which is also called indigenous (i.e., local), autochthonous (indigenous), resident, etc.;

2. optional, or transitory.

Pathogenic microorganisms accidentally penetrating into the macroorganism can periodically be included in the composition of the automicroflora.

The composition of the microflora of the body

2. ATspecies composition and quantitative characteristics of the microflora of the most important areas of the animal body

As a rule, dozens and hundreds of species of various microorganisms are associated with the animal organism. They, as V. G. Petrovskaya and O. P. Marko (1976) write, are obligate for the organism as a whole. Many types of microorganisms are found in many areas of the body, changing only quantitatively. Quantitative variations are possible in the same microflora depending on the type of mammal. Most animals are characterized by general averages for a number of areas of their body. For example, the distal, lower parts of the gastrointestinal tract are characterized by the following microbial groups detected in the contents of the intestine or feces (Table 1).

Table 1. Microflora of the lower gastrointestinal tract

At the top of the table 1. only obligate anaerobic microorganisms are given - representatives of the intestinal flora. It has now been established that strictly anaerobic species in the gut account for 95–99%, while all aerobic and facultative anaerobic species account for the remaining 1–5%. microflora body animal organism

Despite the fact that tens and hundreds (up to 400) known species microorganisms, there may also exist completely unknown microorganisms. Thus, in the caecum and colon of some rodents in recent decades, the presence of so-called filamentous segmented bacteria has been established, which are very intimately associated with the surface (glycocalix, brush border) of the epithelial cells of the intestinal mucosa. The thin end of these long, filamentous bacteria is recessed between the microvilli of the brush border of epithelial cells and appears to be fixed there in such a way that it presses the cell membranes. These bacteria can be so numerous that they, like grass, cover the surface of the mucous membrane. These are also strict anaerobes (obligate representatives of the intestinal microflora of rodents), species useful for the body, largely normalizing intestinal functions. However, these bacteria were detected only by bacterioscopic methods (using scanning electron microscopy of sections of the intestinal wall). Filamentous bacteria do not grow on nutrient media known to us, they can only survive on dense agar media for no more than one week) J . P. Koopman et. al., 1984).

3. Rdistribution of microorganisms in the gastrointestinal tract

Due to the high acidity of gastric juice, the stomach contains a small number of microorganisms; basically it is an acid-resistant microflora - lactobacilli, streptococci, yeast, sardines, etc. The number of microbes there is 10 3 / g of content.

Microflora of the duodenum and jejunum

Microorganisms are everywhere in the intestines. If they were not in any department, then peritonitis of microbial etiology would not occur when the intestine was injured. Only in the proximal parts of the small intestine there are fewer types of microflora than in the large intestine. These are lactobacilli, enterococci, sardines, mushrooms, in the lower sections the number of bifidobacteria, Escherichia coli increases. Quantitatively, this microflora may differ in different individuals. A minimal degree of seeding is possible (10 1 - 10 3 / g of content), and a significant one - 10 3 - 10 4 / g The amount and composition of the microflora of the large intestine are presented in Table 1.

Skin microflora

The main representatives of the skin microflora are diphtherioish (corynebacteria, propionic bacteria), molds, yeasts, spore aerobic bacilli (bacilli), staphylococci (primarily S. epidermidis predominates, but S. aureus is also present in small amounts on healthy skin ).

The microflora of the respiratory tract

On the mucous membranes of the respiratory tract, most of the microorganisms are in the nasopharynx, behind the larynx their number is much less, even less in the large bronchi, and there is no microflora in the depths of the lungs of a healthy body.

In the nasal passages there are diphtheroids, primarily corynebacteria, constant staphylococci (resident S. epidermidis), Neisseria hemophilic bacteria, streptococci (alpha-hemolytic); in the nasopharynx - corynebacteria, streptococci (S. mitts, S. salivarius, etc.), staphylococci, neisseoii, vilonella, hemophilic bacteria; B. subtil is and others.

The microflora of the deeper parts of the respiratory tract has been studied less (A - Halperin - Scottetal ., 1982). In humans, this is due to the difficulties in obtaining material. In animals, the material is more accessible for research (killed animals can be used). We studied the microflora of the middle respiratory tract in healthy pigs, including their miniature (laboratory) variety; the results are presented in table. 2.

Table 2. Microflora of the mucous membrane of the trachea and large bronchi of healthy pigs

The first four representatives were detected constantly (100%), less resident (1/2-1/3 cases) were found: lactobacilli (10 2 -10 3), E. coli (10 2 -11 3), mold fungi (10 2 --10 4), yeast. Other authors noted the transient carriage of Proteus, Pseudomonas aeruginosa, Clostridia, representatives of aerobic bacilli. We once identified Bacteroides melaninoge - nicus in the same plan .

Generic microflorax paths of mammals

Recent studies, mainly by foreign authors (Boyd, 1987; A. B. Onderdonketal., 1986; J. M. Milleretal., 1986; A. N. Masfarietal., 1986; H. Knotheua. 1987), showed that the microflora that colonizes (i.e. inhabits) the mucous membranes of the birth canal is very diverse and rich in species. The components of the normal microflora are widely represented; it contains many strictly anaerobic microorganisms (Table 3).

Table 3. Microflora of the birth canal (vagina, cervix)

If we compare the microbial species of the birth canal with the microflora of other areas of the body, we find that the microflora of the mother's birth canal is similar in this respect to the main groups of microbial inhabitants of the body. of the future young organism, that is, the obligate representatives of its normal microflora, the animal receives when passing through the birth canal of the mother. Further settlement of the body of a young animal occurs from this brood of an evolutionarily substantiated microflora obtained from the mother. It should be noted that in a healthy female, the fetus in the uterus is sterile until the onset of childbirth. However, the properly formed (selected in the process of evolution) normal microflora of the animal's body in full inhabits its body not immediately, but in a few days, having time to multiply in certain proportions. V. Brown gives the following sequence of its formation in the first 3 days of a newborn's life: bacteria are found in the very first samples taken from the body of a newborn immediately after birth. So, on the nasal mucosa, coagulase-negative staphylococci (S. epidermidis) were predominant at first; on the mucous membrane of the pharynx - the same staphylococci and streptococci, as well as a small amount of epterobacteria. In the rectum on the 1st day, E. coli, enterococci, the same staphylococci were already found, and by the third day after birth, a microbial biocenosis was established, mostly normal for the normal microflora of the large intestine (W. Braun, F. Spenckcr u. a. , 1987).

4. Odifferences in the microflora of the body of different animal species

The above obligate representatives of the microflora are characteristic of most domestic, agricultural mammals and the human body. Depending on the type of animal, the number of microbial groups can rather change, but not their species composition. In dogs, the number of Escherichia coli and lactobacilli in the large intestine is the same as shown in Table. 1. However, bifidobacteria were an order of magnitude lower (10 8 per 1 g), streptococci (S. lactis, S. mitis, enterococci) and clostridia were an order of magnitude higher. In rats and mice (laboratory), the number of lactic acid bacilli (lactobacilli) was also increased, more streptococci and clostridia. In these animals, there were few Escherichia coli in the intestinal microflora and the number of bifidobacteria was reduced. The number of Escherichia coli is also reduced in guinea pigs (according to V. I. Orlovsky). In the faeces of guinea pigs, according to our research, Escherichia coli were contained in the range of 10 3 -10 4 per 1 g. up to 10 2 in 1 g) and lactobacilli.

In healthy pigs (according to our data), the microflora of the trachea and large bronchi neither quantitatively nor qualitatively differed significantly from the average indicators and is very similar to the human microflora. Their intestinal microflora was also characterized by a certain similarity. The microflora of the rumen of ruminants is characterized by specific features. This is largely due to the presence of bacteria - fiber breakers. However, cellulolytic bacteria (and, in general, fungal bacteria) characteristic of the digestive tract of ruminants are by no means symbionts of these animals alone. So, in the caecum of pigs and many herbivores, such splitters of cellulose and hemicellulose fibers, common with ruminants, as Bacteroides succinogenes, Ruminococcus flavefaciens, Bacteroides ruminicola and others play an important role (V. H. Varel, 1987).

5. Hnormal microflora of the body and pathogenic microorganisms

Obligate macroorganisms, which are listed above, are mainly representatives of the pepathogenic microflora. Many of the species included in these groups are even called symbionts of the macroorganism (lactobacilli, bifeldobacteria) and are useful for it. Certain beneficial functions have been identified in many non-pathogenic species of clostridia, bacteroids, eubacteria, enterococci, non-pathogenic Escherichia coli, etc. These and other representatives of the microflora of the body are called "normal" microflora. But less harmless, opportunistic and highly pathogenic microorganisms are included in the microbiocenosis physiological for a macroorganism from time to time. In the future, these pathogens can:

- to exist more or less for a long time in the body as part of the entire complex of its automicroflora; in such cases, the carriage of pathogenic microbes is formed, but quantitatively, nevertheless, the normal microflora prevails;

b be forced out (quickly or somewhat later) from the macroorganism by useful symbiotic representatives of the normal (autochthonous) microflora and eliminated;

b multiply, so crowding out the normal microflora that, with a certain degree of colonization of the macroorganism, they can cause the corresponding disease.

In the intestines of animals and humans, for example, in addition to certain types of non-pathogenic clostridia, C. perfringens lives in small numbers. As part of the entire microflora of a healthy animal, the number of C. perfringens does not exceed 10 - 11 5 per 1 g. However, under certain conditions, possibly associated with disturbances in the normal microflora, pathogenic C. perfringens multiplies on the intestinal mucosa in large numbers (10 7 --10 9 or more), causing anaerobic infection. In this case, it even displaces the normal microflora and can be detected in the scarified cata of the ileum mucosa in almost pure culture. In a similar way, the development of intestinal coli infection occurs in the small intestine in young animals, only pathogenic types of Escherichia coli multiply just as rapidly there; in cholera, the surface of the intestinal mucosa is colonized by Vibrio cholerae, etc.

6. Morthofunctional role and metabolic function of the automicroflora of the body

Automicroflora affects the macroorganism after its birth in such a way that under its influence the structure and functions of a number of organs in contact with the external environment mature and form. In this way, the gastrointestinal, respiratory, urogenital tracts and other organs acquire their morphofunctional appearance in an adult animal. A new area of ​​biological science, gnotobiology, which has been successfully developing since the time of L. Pasteur, made it possible to very clearly understand that many immunobiological features of an adult, normally developed animal organism are formed under the influence of the automicroflora of its body. Microbial-free animals (gnotobiots) obtained by caesarean section and then kept for a long time in special sterile gnotobibological isolators without any access to them of any viable microflora have features of the embryonic state of the mucous membranes that communicate with the external environment of the organs. Their immunobiological status also retains embryonic features. Observe hypoplasia of the lymphoid tissue in the first place of these organs. Microbial-free animals have fewer immunocompetent cellular elements and immunoglobulins. However, it is characteristic that the organism of such a gnotobiotic animal potentially remains capable of developing immunobiological capabilities, and only because of the absence of antigenic stimuli that come from automicroflora in ordinary animals (starting from birth), it did not undergo a naturally occurring development that affects the entire immune system in in general, and local lymphoid accumulations of the mucous membranes of organs such as the intestines, respiratory tract, eye, nose, ear, etc. Thus, in the process individual development of the animal organism, it is from its automicroflora that the effects follow, including antigenic stimuli, which determine the normal immunomorphofunctional state of an ordinary adult animal.

The microflora of the animal body, in particular the microflora of the gastrointestinal tract, performs important metabolic functions for the body: it affects absorption in the small intestine, its enzymes are involved in the degradation and metabolism of bile acids in the intestine, and forms unusual fatty acids in the digestive tract. Under the influence of microflora, there is a catabolism of some digestive enzymes of the macroorganism in the intestine; enterokinase, alkaline phosphatase are inactivated, decompose, some immunoglobulins of the digestive tract that have fulfilled their function are decomposed in the large intestine, etc. The microflora of the gastrointestinal tract is involved in the synthesis of many vitamins necessary for the macroorganism. Its representatives (for example, a number of types of bacteroids, anaerobic streptococci, etc.) with their enzymes are able to break down fiber, pectin substances that are indigestible by the animal body on its own.

FROMlist of literature

1. Baltrashevich A. K. et al. dense medium without blood and its semi-liquid and liquid variants for the cultivation of bacteroids / Scientific Research Laboratory of Experimental Biological Models of the USSR Academy of Medical Sciences. M. 1978 7 p.

2. Goncharova G. I. To the method of cultivation of V. bifidum // Laboratory business. 1968. No. 2. S. 100--102.

3. I. N. Blokhina E, S. Voronin, et al. Guidelines on the isolation and identification of opportunistic enterobacteria and salmonella in acute intestinal diseases of young farm animals / M: MVA, 1990. 32 p.

4. Petrovskaya V. G., Marko O. P. Human microflora in health and disease. Moscow: Medicine, 1976. 221 p.

5. Chakhava O. V. et al. Microbiological and immunological foundations of gnotobiology. Moscow: Medicine, 1982. 159 p.

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