RELATIONSHIP OF MICROORGANISMS WITH HUMANS AND ANIMALS
RELATIONSHIP OF MICROORGANISMS WITH PLANTS
Microflora of the rhizosphere. Plants release various organic compounds- sugars, organic acids, nucleotides, amino acids, vitamins, growth stimulants, which are an easily accessible and very diverse substrate for feeding microorganisms. Therefore, it is no coincidence that root system and terrestrial organs of plants are abundantly populated by microorganisms. In turn, the microflora of the rhizosphere, taking part in the processes of transformation of organic substances in the soil, provides plants with the necessary elements mineral nutrition, as well as some biologically active substances. In addition, rhizosphere microorganisms decompose many compounds toxic to plants, disinfecting the soil. Degree mutual influence plants and bacteria is determined by their contact.
Phytopathogenic microorganisms. Almost all groups of microorganisms contain pathogens of plant diseases. The first place among phytopathogenic microbes belongs to fungi, the second place is occupied by viruses and bacteria, and only a small percentage of plant diseases are caused by actinomycetes.
Most phytopathogenic microorganisms actively synthesize hydrolytic enzymes (pectipases, cellulases, proteases, etc.), causing maceration of plant tissues and destruction of cell membranes, which leads to the penetration of the pathogen into the cell. Having penetrated the cell, phytopathogenic microbes disrupt the normal course of physiological processes, primarily photosynthesis and respiration. Toxins released by the pathogen inactivate enzymes plant cell which ultimately leads to her death.
A set of microorganisms that have adapted to life in the body of humans and animals 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. Obligate microflora includes relatively permanent saprophytic and conditionally pathogenic microorganisms that are maximally adapted to existence in the host’s body. Facultative microflora is random and temporary. It is determined by the intake of microorganisms from the environment, as well as the state of the immune system of the macroorganism.
IN oral cavity In humans and animals, the bulk of bacteria is localized in dental plaque. 1 g of dry mass of dental plaque contains at least 250 million microbial cells.
There are almost no microorganisms in the human stomach, which is due to the bactericidal effect of gastric juice and the acidic pH reaction.
The small intestine contains relatively few bacteria (10 2 -10^), predominantly aerobic forms. But in the large intestine there is a colossal number of microbes, including more than 260 different types facultative and obligate anaerobes.
From the surrounding air, along with dust, a lot of microbes enter the respiratory tract of humans and animals. Due to the protective function of the epithelium and the bactericidal effect of lysozyme and mucin of the nasal mucosa, most microorganisms are retained in the upper respiratory tract. The bronchi and alveoli of the lungs are practically sterile. As part of the microflora of the upper respiratory tract contains relatively permanent microbes represented by staphylococci, corynebacteria, streptococci, bacteroides, capsule gram-negative bacteria, etc.
The substrate for feeding bacteria on the surface of the skin is the secretions of the sweat and sebaceous glands, as well as dying epithelial cells. The skin of exposed parts of the body - hands, face, neck - is richest in microorganisms. The overwhelming majority of skin microorganisms are represented by saprophytic bacteria - staphylococci, bacilli, mycobacteria, corynebacteria and yeast fungi, and only 5% of analyzes isolate an opportunistic microbe - Staphylococcus aureus.
Normal microflora in the human and animal body plays an important role in the formation of natural immunity. It has been established that obligate microorganisms that produce 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 microboienoses in the human body are called dysbacteriosis. The latter occurs most often as a result of long-term use of antibiotics, as well as chronic infections, radiation and exposure to extreme factors. The development of dysbiosis is explained by the suppression of the obligate microflora of the macroorganism and, accordingly, the active reproduction of opportunistic bacteria (Proteus, Pseudomonas) and yeast fungi Candida al-bicans.
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A set of microorganisms that have adapted to life in the body of humans and animals 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. Obligate microflora includes relatively permanent saprophytic and opportunistic microorganisms that are maximally adapted to existence in the host’s body. Facultative microflora is random and temporary. It is determined by the intake of microorganisms from the environment, as well as the state of the immune system of the macroorganism.
The permanent inhabitants of the oral cavity are streptococci, lactobacilli, corynebacteria, bacteroides, as well as yeast fungi, actinomycetes, mycoplasmas and protozoa. Facultative inhabitants include enterobacteriaceae, spore-forming bacteria and Pseudomonas aeruginosa. Availability Escherichia coli is an indicator of poor oral health.
Main role Saliva, which contains various enzymes with antibacterial activity, plays a role in maintaining the qualitative and quantitative composition of microorganisms in the oral cavity.
There are almost no microorganisms in the human stomach. Sometimes found in the stomach in small quantities Sarcina ventriculi, Bacillus subtilis and some yeast.
The small intestine contains relatively few bacteria (10 2 –10 3), predominantly 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 bacteroides, bifidobacteria, fecal streptococcus, Escherichia coli, and 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 microorganisms are retained in the upper respiratory tract. The bronchi and alveoli of the lungs are practically sterile. The microflora of the upper respiratory tract contains relatively permanent microbes, represented by staphylococci, corynebacteria, streptococci, bacteroides, capsular gram-negative bacteria, etc. In addition to bacteria, some viruses, in particular adenoviruses, can remain in a latent state for a long time in the upper respiratory tract.
The substrate for feeding bacteria on the surface of the skin is the secretions of the sweat and sebaceous glands, as well as dying epithelial cells. The skin of exposed parts of the body – hands, face, neck – is richest in microorganisms. The overwhelming majority of skin microorganisms are represented by saprophytic bacteria - staphylococci, bacilli, mycobacteria, corynebacteria and yeast fungi, and only 5% of analyzes isolate an opportunistic microbe - Staphylococcus aureus. During sanitary and bacteriological tests, the detection of Escherichia coli on the surface of the skin indicates contamination with feces.
Normal microflora in the human and animal body plays an important role in the formation of natural immunity. Obligate microorganisms that produce 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. Dysbiosis occurs most often as a result of long-term use of antibiotics, as well as chronic infections, radiation and exposure to 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 microorganisms? Give examples of these groups of microorganisms.
4. What is the importance of water for microorganisms?
5. Explain the mechanism of action of different types of irradiation on microorganisms. Which 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 the different sensitivity of microorganisms to the pH of the environment. 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.
Microflora of the animal body and its physiological significance
Some microorganisms are permanent inhabitants of the animal body. Others are temporary - come with water, food, air.
M/f skin. Post-s: staphylococci, streptococci, actinomycetes, sarcina, kish-aya and Pseudomonas aeruginosa. sticks. Depends on the conditions of detention.
M/f breath. ways. In newborns. No. Streptococci, staphylococci, actinomycetes, mycoplasmas, molds. and trembling mushrooms.
M/f stomach. Poor due to gastric juice and acidic environment. Sarcines, lactic acid bacteria, actinomycetes, enterococci.
M/f scar. Richer due to epiphytic and soil m/f. Origin complex biochemical and microbiol. processes involving cellulose-forming bacteria. Putrefactive bacteria and fermentation.
M/f thin. Poorer. Enterococci, acidophilus, spore microbes. actinom., Escherichia coli.
M/f thick. The richest. Enterococci, staph, strept, yeast, mold, actin, putrefactive m/o. In case of pain, they are found in the feces of encounters. pathogen. m/o, which can infect healthy people (convalescents).
M/f genitourinary. organs. In healthy people only in external areas. staf, strep, micrococci, mycobacteria..
The role of m/f: the formation of immune activity, antagonism of pathogenic m/f, affects the functions of the digestive tract, is taken into account in the circulation of bile components, the breakdown of fiber and other feed components.
Distribution of microbes in nature
Distribution is facilitated by small sizes, negligible weight, enormous speed reproduction, the ability to adapt to environmental changes. environment, temperature factor.
Microflora of air and water. Quantitative and qualitative determination of air and water microflora
The water is most populated at 10-100 cm depth. The UFL applies above. Self-purification of a reservoir: fast flow, UV rays, organic mineralization. compounds by microorganisms, t. In everyday life - filters. IN clean waters Cocci predominate; in contaminated ones, rods predominate. May be pathogenic: anthrax, brucellosis, erysipelas, pasteurellosis.. Coli titer is the minimum (GOST 333) V of water in which 1 Escherichia coli is detected. Coli index - the number of E. coli in 1 liter of water (GOST 2-3).
Air is an unfavorable environment for m/o. But a short stay of microorganisms in the air is sufficient for the transmission of pathogens from patients. Depends on room ventilation and sanitary and hygienic standards. Saprophytes: micrococci, rods, molds and yeasts, actinomycetes. Opportunistic: fungal spores. Pathogenic: mycobacteria, pneumococci, streptococci.
Determination of air and water microflora:
1. OMC: For water - take a water sample using bathometers, make dilutions of 1:10, 1:100, pour in MPA, put in a thermostat for 24 hours at 37 degrees, then count the grown colonies. Norm for drinking water no more than 100 CFU (colony-forming units).
For air - sedimentation method (Petri dish with MPA, thermostat, counting), aspiration method using Krotov’s apparatus (the device sucks in air, settles on a Petri dish with a dense medium, counting), filtration method, including Dyakov’s method (air is passed through MPA and glass beads, filled with a special medium for staphylococci and streptococci, counted)
2. Sanitary indicator microbes: For water - general (TKB 37 degrees) and thermotolerant (TCB 44 degrees) coliform bacteria - coliform bacteria (coliforms). The coli-titer and coli-index are also determined using membrane filter methods (membrane filters are placed on a Seitz asbestos filter, water is filtered, transferred to Endo in a Petri dish with tweezers, incubated, coliforms are counted (Gr-, oxidase-, spores-, lactose+) ), fermentation meth (inoculation on Kessler's medium with lactose, incubation, subculture on Endo, coliforms are counted). Enterococci - an alkaline-polymyxin environment. Cl. Perfringens - Wilson-Blair medium, iron sulfite agar.
For air - hemolytic streptococci, staphylococci (salt media - Chistovich).
3. Pathogenic microorganisms.
Intizarov Mikhail Mikhailovich, academician of the Russian Academy of Agricultural Sciences, prof..
PREFACE
When considering ways to combat many infectious diseases of bacterial and viral etiology, attention is often focused on pathogenic microorganisms that cause these diseases, and attention is less often paid to the accompanying normal microflora of the animal body. But in a number of cases, it is the ordinary microflora that becomes of great importance in the occurrence or development of the disease, promoting or preventing its manifestation. Sometimes ordinary microflora becomes the source of those pathogenic or conditionally pathogenic infectious agents that cause endogenous infection, the manifestation of second infections, etc. Under other circumstances, the complex of ordinary microflora of the animal’s body blocks the paths and possibilities for the development of the infectious process caused by certain pathogenic microorganisms. Therefore, doctors, biologists, livestock workers, university teachers and scientists should know the composition, properties, quantitative characteristics, biological significance of different groups and representatives of the body’s normal microflora (mammals, including domestic animals, farm animals and humans).
Introduction
The microflora of mammals, including farm animals, 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 collaborators. Thus, in 1885, T. Escherich isolated from the feces of children an obligatory representative of the intestinal microflora - E. coli, which is found in almost all mammals, birds, fish, reptiles, amphibians, insects, etc. After 7 years, the first data appeared on the importance of intestinal sticks for vital activity, health of the macroorganism. S. O. Jensen (1893) found that different types and strains of E. coli can be both pathogenic for animals (causing septic disease and diarrhea in calves) and non-pathogenic, i.e. completely harmless and even useful inhabitants intestines of animals and humans. In 1900, G. Tissier discovered bifid bacteria and limes in the feces of newborns and obligatory representatives of the normal intestinal microflora of the body during all periods of its life. Lactic acid rods (L. acidophilus) were isolated by Moreau in 1900.
Definitions, 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 contributes to maintaining the healthy status of the macroorganism and the correct performance of its normal physiological functions. The entire microflora of an animal’s body can also be called automicroflora (according to the meaning of the word “auto”), that is, microflora of any composition (O. V. Chakhava, 1982) of a given organism normally and in pathology.
A number of authors divide the normal microflora, associated only with the healthy status of the body, into two parts:
1) obligate, permanent part, formed in phylogenesis and ontogenesis V the process of evolution, which is also called indigenous (i.e. local), autochthonous (indigenous), resident, etc.;
2) optional, or transitory.
The composition of the automicroflora may periodically include pathogenic microorganisms that accidentally penetrate into the macroorganism.
Species composition and quantitative characteristicsmicroflora of the most important areas of the animal’s body
As a rule, tens and hundreds of species of various microorganisms are associated with an animal’s body. They , as V.G. Petrovskaya and O.P. Marko (1976) write, they are obligate for the organism as a whole. Many types of microorganisms are found in many areas of the body, varying only quantitatively. Quantitative variations are possible in the same microflora depending on the species of mammal. Most animals are characterized by general average indicators 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 identified in the intestinal contents or feces (Table 1).
At the top of the table. 1. Only obligate anaerobic microorganisms are shown - representatives of the intestinal flora. It has now been established that strictly anaerobic species in the intestine account for 95-99%, and all-aerobic and facultative anaerobic species account for the remaining 1-5%.
Despite the fact that tens and hundreds (up to 400) of known species of microorganisms live in the intestines, completely unknown microorganisms can also exist there. Thus, in the cecum and colon of some rodents in last decades The presence of so-called filamentous segmented bacteria was established, which are very intimately associated with the surface (glycocalyx, brush border) of 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 so as to press against the cell membranes. There can be so many of these bacteria that, like grass, they cover the surface of the mucous membrane. These are also strict anaerobes (obligate representatives of the intestinal microflora of rodents), beneficial species for the body, which largely normalize intestinal functions. However, these bacteria were detected only by bacterioscopic methods (using electron scanning microscopy of sections of the intestinal wall). Filamentous bacteria do not grow on nutrient media known to us; they can only survive on solid agar media for no more than one week) J. P. Koopman et. al ., 1984).
Distribution of microorganisms among parts of the gastrointestinal tract
Due to the high acidity of gastric juice, the stomach contains a small number of microorganisms; These are mainly 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
There are microorganisms in the intestines. If they were not present in any department, then peritonitis of microbial etiology would not occur due to intestinal injury. Only in the proximal parts of the small intestine are there fewer types of microflora than in the large intestine. These are lactobacilli, enterococci, sardines, mushrooms, in the lower sections the number of bifidobacteria and E. coli increases. Quantitatively, this microflora may differ in different individuals. A minimal degree of contamination is possible (10 1 - 10 3 /g contents), 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 diphtherois (corynebacteria, propionic bacteria), molds, yeasts, spore-bearing aerobic bacilli (bacillus), staphylococci (primarily S. epidermidis predominates, but S. aureus is also present in small quantities on healthy skin) .
Microflora of the respiratory tract
On the mucous membranes of the respiratory tract, the most microorganisms are in the nasopharynx area, behind the larynx their number is much smaller, even less in the large bronchi, and in the depths of the lungs of a healthy organism there is no microflora at all.
In the nasal passages there are diphtheroids, primarily corneabacteria, permanent staphylococci (resident S. epi dermidis), neisseria, hemophilus bacteria, streptococci (alpha-hemolytic); in the nasopharynx - corynebacteria, streptococci (S. mitts, S. salivarius, etc.), staphylococci, Neisseoii, ViloNella, hemophilus bacteria, enterobacteria, bacteroides, fungi, enterococci, lactobacilli, Pseudomonas aeruginosa, aerobic bacilli type B. subtil are more transiently found is, etc.
The microflora of the deeper parts of the respiratory tract has been studied less (A - Halperin - Scott et al., 1982). In humans, this is due to 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.
The first four representatives were identified constantly (100%), less resident (1/2-1/3 cases) were identified: lactobacilli (10 2 -10 3), Escherichia coli (10 2 -III 3), molds (10 2 -10 4), yeast. Other authors noted transient carriage of Proteus, Pseudomonas aeruginosa, clostridia, and representatives of aerobic bacilli. In this regard, we once identified Bacteroides melaninoge - nicus.
Microflora of the birth canal of mammals
Research in recent years, mainly by foreign authors (Boyd, 1987; A. B. Onderdonk et al., 1986; J. M. Miller et al., 1986; A. N. Masfari et al., 1986; H. Knothe u . a. 1987), showed that the microflora that colonizes (i.e., populates) the mucous membranes of the birth canal is very diverse and rich in species. The components of normal microflora are widely represented; it contains many strictly anaerobic microorganisms (Table 3).
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. The animal receives the future young organism, that is, obligate representatives of its normal microflora when passing through the mother’s birth canal. Further colonization of the body of a young animal occurs from this brood of evolutionarily based microflora received from the mother. It should be noted that in a healthy female, the fetus in the uterus is sterile until labor begins.
However, the correctly formed (selected in the process of evolution) normal microflora of an animal’s body does not fully inhabit its body immediately, but within a few days, managing 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 detected in the very first samples taken from the newborn’s body immediately after birth. Thus, on the nasal mucosa, coagulase-negative staphylococci (S. epidermidis) were initially predominant; on the pharyngeal mucosa - the same staphylococci and streptococci, as well as a small amount of epterobacteria. In the rectum on the 1st day, E. coli, enterococci, and the same staphylococci were already found, and by the third day after birth, a microbial biocenosis was established, mostly common for the normal microflora of the large intestine (W. Braun, F. Spenckcr u. a. , 1987).
Differences in the body microflora of different animal species
The above obligate representatives of the microflora are characteristic of most domestic and agricultural mammals and the human body. Depending on the type of animal, the number of microbial groups may change, but not their species composition. In dogs, the number of E. 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 in 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 (lactic acid bacteria) was increased by the same amount, and there were more streptococci and clostridia. These animals had few E. coli in their intestinal microflora and the number of bifidobacteria was reduced. The number of E. coli is also reduced in guinea pigs (according to V.I. Orlovsky). In the feces of guinea pigs, according to our research, E. coli were contained within 10 3 -10 4 per 1 g. In rabbits, bacteroids predominated (up to 10 9 -10 10 per 1 g), the number of E. coli was significantly reduced (often even up to 10 2 in 1 g) and lactobacilli.
In healthy pigs (according to our data), the microflora of the trachea and large bronchi was neither quantitatively nor qualitatively noticeably different from the average indicators and was very similar to the human microflora. Their intestinal microflora was also characterized by certain similarities.
The rumen microflora of ruminants is characterized by specific features. This is largely due to the presence of bacteria that break down fiber. However, cellulolytic bacteria (and fibrolytic bacteria in general), characteristic of the digestive tract of ruminants, are by no means symbionts of these animals alone. Thus, in the cecum of pigs and many herbivores, an important role is played by such breakers of cellulose and hemicellulose fibers, common to ruminants, as Bacteroides succi-nogenes, Ruminococcus flavefaciens, Bacteroides ruminicola and others (V. H. Varel, 1987).
Normal microflora of the body and pathogenic microorganisms
The obligate macroorganisms listed above are mainly representatives of the pepathogenic microflora. Many species included in these groups are even called symbionts of the macroorganism (lactobacteria, bifldobacteria) and are useful for it. Certain useful features found in many non-pathogenic species of clostridia, bacteroides, eubacteria, enterococci, non-pathogenic Escherichia coli, etc. These and other representatives of the body microflora are called “normal” microflora. But from time to time, less harmless, opportunistic and highly pathogenic microorganisms are also included in the microbiocenosis that is physiological for the macroorganism. In the future, these pathogens may:
a) exist in the body for a more or less long time
as part of the entire complex of its automicroflora; in such cases, a carriage of pathogenic microbes is formed, but quantitatively, normal microflora still prevails;
b) be forced out (quickly or somewhat later) from the macroorganism by beneficial symbiotic representatives of normal microflora and eliminated;
c) multiply, displacing the normal microflora in such a way that, with a certain degree of colonization of the macroorganism, they can cause a 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 quantities. In the entire microflora of a healthy animal, the amount of C. perfringens does not exceed 10-15 milliards per 1 g. However, in the presence of certain conditions, possibly associated with disturbances in the normal microflora, pathogenic C. perfringens multiplies on the intestinal mucosa in a huge number(10 7 -10 9 or more), causing an anaerobic infection. In this case, it even displaces the normal microflora and can be detected in the scarification of the ileal mucosa in almost pure culture. In a similar way, intestinal co-infection develops in the small intestine of young animals, only pathogenic types of E. coli multiply just as rapidly there; with cholera, the surface of the intestinal mucosa is colonized by Vibrio cholerae, etc.
Biological role ( functional value) normal microflora
During the life of an animal, pathogenic and conditionally pathogenic microorganisms periodically come into contact and penetrate into its body, becoming part of the general microflora complex. If these microorganisms cannot immediately cause a disease, then they coexist with other microflora of the body for some time, but are more often transient. Thus, for the oral cavity, among pathogenic and conditionally pathogenic facultative transient microorganisms, P, aeruginosa, C. perfringens, C. albicans, representatives (of the genera Esoherichia, Klebsiella, Proteus; for the intestine they are also even more pathogenic enterobacteria, as well as B fragilis, C. tetani, C. sporogenes, Fusobacterium necrophorum, some representatives of the genus Campylobacter, intestinal spirochetes (including pathogenic, opportunistic) and many others. S. aureus is characteristic of the skin and mucous membranes; tract - also known as pneumococci, etc.
However, the role and significance of the beneficial, symbiotic normal microflora of the body is that it does not easily allow these pathogenic facultative-transient microorganisms into its environment, into the spatial ecological niches already occupied by it. The above representatives of the autochthonous part of the normal microflora were the first, even during the passage of the newborn through the mother’s birth canal, to take their place on the animal’s body, that is, to colonize its skin, gastrointestinal and respiratory tracts, genitals and other areas of the body.
Mechanisms that prevent colonization (invasion) of the animal body by pathogenic microflora
It has been established that the largest populations of the autochthonous, obligate part of the normal microflora occupy characteristic places in the intestine, a kind of territory in the intestinal microenvironment (D. Savage, 1970). We studied this ecological feature of bifidobacteria and bacteroides and found that they are not distributed evenly in the chyme throughout the entire cavity of the intestinal tube, but are spread out in stripes and layers of mucus (mucins) that follow all the bends of the surface of the mucous membrane of the small intestine. In part, they are adjacent to the surface of the epithelial cells of the mucosa. Since bifidobacteria, bacteroides and others colonize these subregions of the intestinal microenvironment first, they create obstacles for many pathogenic microorganisms that later penetrate the intestine to approach and fixate (adhesion) on the mucous membrane. And this is one of the leading factors, since it has been established that in order to realize their pathogenicity (the ability to cause disease), any pathogenic microorganisms, including those that cause intestinal infections, must adhere to the surface of intestinal epithelial cells, then multiply on it, or, penetrating deeper, colonize these same or similar subregions, in the area of which huge populations have already developed, for example, bifidobacteria. It turns out that in this case, the bifid flora of a healthy body shields the intestinal mucosa from some pathogens, limiting their access to the surface of epithelial cell membranes and to receptors on epithelial cells on which pathogenic microbes need to fixate.
For many representatives of the autochthonous part of the normal microflora, a number of other mechanisms of antagonism towards pathogenic and opportunistic microflora are known:
Production of volatile fatty acids with a short chain of carbon atoms (they are formed by the strictly anaerobic part of normal microflora);
Formation of free bile metabolites (lactobacteria, bifidobacteria, bacteroides, enterococci and many others can form them by deconjugating bile salts);
Lysozyme production (characteristic of lactobacilli, bifidobacteria);
Acidification of the environment during the production of organic acids;
Production of colicins and bacteriocins (streptococci, staphylococci, Escherichia coli, Neisseria, propyaonic bacteria, etc.);
Synthesis of various antibiotic-like substances by many lactic acid microorganisms - Streptococcus lactis, L. acidophilus, L. fermentum, L. brevis, L. helveticus, L. pjantarum, etc.;
Competition of non-pathogenic microorganisms related to pathogenic species with pathogenic species for the same receptors on the cells of the macroorganism, to which their pathogenic relatives must also attach;
Absorption by symbiotic microbes from the normal microflora of some important components and elements of nutritional resources (for example, iron) necessary for the life of pathogenic microbes.
Many of these mechanisms and factors present in representatives of the microflora of the animal’s body, when combined and interacting, create a kind of barrier effect - an obstacle to the proliferation of opportunistic and pathogenic microorganisms in certain areas of the animal’s body. The resistance of a macroorganism to colonization by pathogens, created by its usual microflora, is called colonization resistance. This resistance to colonization by pathogenic microflora is created mainly by a complex of beneficial species of strictly anaerobic microorganisms that are part of the normal microflora: various representatives of the genera - Bifidobacterium, Bacteroides, Eubacterium, Fusobacterium, Clostridium (non-pathogenic), as well as facultative anaerobes, for example, the genus Lactobacill - lus , non-pathogenic E. coli, S. faecalis, S. faecium and others. It is this part of the strictly anaerobic representatives of the normal microflora of the body that dominates in population size in the entire intestinal microflora within 95-99%. For these reasons, the normal microflora of the body is often considered an additional factor in the nonspecific resistance of the body of a healthy animal and human.
It is very important to create and maintain conditions under which the colonization of the newborn with normal microflora is directly or indirectly formed. Veterinary specialists, administrative and economic workers, and livestock breeders must properly prepare mothers for childbirth, conduct childbirth, and ensure colostrum and milk feeding of newborns. We must take care of the state of the normal microflora of the birth canal.
Veterinary specialists should keep in mind that the normal microflora of the birth canal of healthy females is that physiologically based breeding of beneficial microorganisms, which will determine the correct development of the entire microflora of the body of the future animal. If the birth is uncomplicated, then the microflora should not be disturbed by unjustified therapeutic, preventive and other influences; do not introduce antiseptic agents into the birth canal without sufficiently compelling indications; use antibiotics judiciously.
ConceptOdysbacteriosis
There are cases when the evolutionarily established ratio of species in the normal microflora is violated or the quantitative relationships between the most important groups microorganisms of the body's automicroflora, or the quality of the microbial representatives themselves changes. In this case, dysbiosis occurs. And this opens the way for pathogenic and conditionally pathogenic representatives of the automicroflora, which can invade or multiply in the body and cause diseases, dysfunctions, etc. The correct design of the normal microflora that has developed in the process of evolution, its eubiotic state, restrains the conditionally pathogenic part within certain limits automicroflora of the animal body.
Morphofunctional role and metabolic function of the body's automicroflora
Automicroflora influences 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 they acquire their morphofunctional appearance in an adult animal. gastrointestinal, respiratory, genitourinary tracts and other organs. New area biological spiders - gnotobiology, which has been successfully developing since the time of L. Pasteur, has 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. Germ-free animals (gnotobiotes), obtained by Caesarean section and then kept for a long time in special sterile gnotobiological isolators without any access to them by any viable microflora, have features of the embryonic state of the mucous membranes communicating with the external environment of the organs. Their immunobiological status also retains embryonic features. Hypoplasia of lymphoid tissue is observed primarily in these organs. Germ-free animals have fewer immunocompetent cellular elements and immunoglobulins. However, it is characteristic that potentially the organism of such a gnotobiotic animal remains capable of developing immunobiological capabilities, and only due to the lack of antigenic stimuli coming from the 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's body, it is precisely from its automicroflora that effects follow, including antigenic stimuli, which determine the normal immunomorphofunctional state of an ordinary adult animal.
The microflora of an animal's 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 participate 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, the catabolism of some digestive enzymes of the macroorganism occurs in the intestine; enterokinase and alkaline phosphatase are inactivated, disintegrating, in the large intestine some immunoglobulins of the digestive tract are disintegrating, having fulfilled their function, 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 species of bacteroides, anaerobic streptococci, etc.) with their enzymes are capable of breaking down fiber and pectin substances that are indigestible by the animal body on its own.
Some methods for monitoring the state of the microflora of an animal's body
Monitoring the state of the microflora in specific animals or their groups will make it possible to timely correct undesirable changes in the important autochthonous part of the normal microflora, correct violations through the artificial introduction of beneficial bacterial representatives, for example bifidobacteria or lactobacilli, etc., and prevent the development of dysbiosis in very severe forms. Such control is possible if microbiological studies are carried out at the right time. species composition and quantitative relationships, primarily in the autochthonous strictly anaerobic microflora of some areas of the animal’s body. For bacteriological examination, mucus is taken from the mucous membranes, the contents of organs, or even the organ tissue itself.
Taking material. To examine the large intestine, feces can be used, collected specifically using sterile tubes - catheters - or other methods in sterile containers. Sometimes it is necessary to take the contents of different parts of the gastrointestinal tract or other organs. This is possible mainly after the slaughter of animals. In this way, it is possible to obtain material from the jejunum, duodenum, stomach, etc. Taking sections of the intestine along with their contents makes it possible to determine the microflora of both the cavity of the digestive canal and the intestinal wall by preparing scrapings, homogenates of the mucous membrane or intestinal wall. Taking material from animals after slaughter also allows for a more complete and comprehensive determination of the normal microflora of the birth upper and middle respiratory tract (trachea, bronchi, etc.).
Quantitative research. To determine the quantities of different microorganisms, material taken from an animal in one way or another is used to prepare 9-10 tenfold dilutions of it (from 10 1 to 10 10) in a sterile saline solution or some (corresponding to the type of microbe) sterile liquid nutrient medium. Then, from each dilution, starting from less to more concentrated, they are sown on appropriate nutrient media.
Since the samples under study are biological substrates with mixed microflora, it is necessary to select media in such a way that each satisfies the growth needs of the desired microbial genus or species and simultaneously inhibits the growth of other accompanying microflora. Therefore, it is desirable that the media be selective. In terms of biological role and significance in normal microflora, its autochthonous, strictly anaerobic part is more important. Techniques for its detection are based on the use of appropriate nutrient media and special methods of anaerobic cultivation; Most of the above strictly anaerobic microorganisms can be cultivated on a new, enriched and universal nutrient medium No. 105 by A.K. Baltrashevich et al. (1978). This medium has a complex composition and therefore can satisfy the growth needs of a wide variety of microflora. A description of this environment can be found in the manual “Theoretical and Practical Foundations of Gnotobiology” (M.: Kolos, 1983). Various versions of this medium (without the addition of sterile blood, with blood, dense, semi-liquid, etc.) make it possible to grow many obligate anaerobic species, in anaerostats in a gas mixture without oxygen and outside anaerostats, using a semi-liquid version of medium No. 105 in test tubes.
Bifidobacteria also grow on this medium if 1% lactose is added to it. However, due to the extremely large quantity not always available components and the complex composition of medium No. 105 may cause difficulties in its manufacture. Therefore, it is more advisable to use Blaurock’s medium, which is no less effective when working with bifidobacteria, but simpler and more accessible to manufacture (Goncharova G.I., 1968). Its composition and preparation: liver decoction - 1000 ml, agar-agar - 0.75 g, peptone - 10 g, lactose - 10 g, cystine - 0.1 g, table salt (chemical salt) - 5 g. First, prepare the liver decoction decoction: 500 g of fresh beef liver, cut into small pieces, add 1 liter of distilled water and boil for 1 hour; settle and filter through a cotton-gauze filter, add distilled water to the original volume. Melted agar-agar, peptone and cystine are added to this decoction; set pH = 8.1-8.2 using 20% sodium hydroxide and boil for 15 minutes; let sit for 30 minutes And filtered. The filtrate is brought to 1 liter with distilled water and lactose is added to it. Then pour 10-15 ml into test tubes and sterilize fractionally with flowing steam (Blokhina I.N., Voronin E.S. et al., 1990).’
To impart selective properties to these media, it is necessary to introduce appropriate agents that inhibit the growth of other microflora. To identify bacteroids, these are neomycin, kanamycin; for spirally curved bacteria (for example, intestinal spirochetes) - spectinomycin; for anaerobic cocci of the genus Veillonella - vancomycin. To isolate bifidobacteria and other gram-positive anaerobes from mixed populations of microflora, sodium azide is added to the media.
To determine the quantitative content of lactobacilli in the material, it is advisable to use Rogosa salt agar. Selective properties are given to it by adding acetic acid, creating pH=5.4 in this environment.
A non-selective medium for lactobacilli can be milk hydrolyzate with chalk: to a liter of pasteurized, skim milk (pH -7.4-7.6), which does not contain antibiotic impurities, add 1 g of pancreatin powder and 5 ml of chloroform; shake periodically; put in a thermostat at 40° C for 72 hours. Then filter, set pH = 7.0-7.2 and sterilize at 1 atm. 10 min. The resulting hydrolyzate is diluted with water 1:2, 45 g of chalk powder sterilized by heating and 1.5-2% agar-agar are added, heated until the agar melts and sterilized again in an autoclave. Before use, the medium is mowed. If desired, any selection agent can be introduced into the medium.
You can identify and determine the level of staphylococci on a fairly simple nutrient medium - glucose salt meat peptone agar (MPA with 10% table salt and 1-2% glucose); enterobacteria - on Endo medium and other media, recipes for which can be found in any microbiology manuals; yeast and mushrooms - on Sabouraud's medium. It is advisable to identify actinomycetes on Krasilnikov’s CP-1 medium, consisting of 0.5 potassium phosphate disubstituted. 0.5 g magnesium sulfate, 0.5 g sodium chloride, 1.0 g potassium nitrate, 0.01 g iron sulfate, 2 g calcium carbonate, 20 g starch, 15-20 g agar-agar and up to 1 liter of distilled water . Dissolve all ingredients, mix, heat until the agar melts, set pH = 7, filter, pour into test tubes, sterilize in an autoclave at 0.5 atm. 15 minutes, mow before sowing.
To identify enterococci, a selective medium (agar-M) is desirable in a simplified version of the following composition: to 1 liter of molten sterile MPA, add 4 g of disubstituted phosphate, dissolved in a minimum amount of sterile distilled water, 400 mg of also dissolved sodium aeide; 2 g of dissolved glucose (or a ready-made sterile solution of 40% glucose - 5 ml). Move everything. After the mixture has cooled to approximately 50° C, add TTX (2,3,5-triphenyltetrazolium chloride) - 100 mg, dissolved in sterile distilled water. Stir, do not sterilize the medium, immediately pour into sterile Petri dishes or test tubes. Entero cocci grow on this medium in the form of small, gray-white colonies. But more often, due to the admixture of TTX, colonies of eutherococci acquire a dark cherry color (the entire colony or its center).
Spore-bearing aerobic bacilli (B. subtilis and others) are easily identified after heating the test material at 80° C for 30 minutes. Then the heated material is inoculated with either MPA or 1MPB and after normal incubation (37 ° C with access to oxygen), the presence of these bacilli is determined by their growth on the surface of the medium in the form of a film (on MPB).
The number of corynebacteria in materials from various areas of the animal’s body can be determined using Buchin’s medium (produced in ready-made form by the Dagestan Institute of Dry Nutrient Media). It can be enriched by adding 5% sterile blood. Neisseria are detected on Bergea's medium with ristomycin: to 1 liter of molten Hottinger agar (less desirable MPA), add 1% maltose, sterilely dissolved in distilled water (you can dissolve 10 g of maltose in a minimum amount of water and boil in a water bath), 15 ml of 2% - solution of water-soluble blue (aniline blue water-soluble), solution of ristomycin from; calculation 6.25 units. per 1 ml of medium. Mix, do not sterilize, pour into sterile Petri dishes or test tubes. Gram-negative cocci of the genus Neisseria grow in the form of small and medium-sized colonies of blue or of blue color. Haemophilus influenzae bacteria can be isolated on a medium consisting of chocolate agar (from horse blood) with bacitracin as a selective agent. .
Methods for identifying opportunistic microorganisms (Pseudomonas aeruginosa, Proteus, Klebsiella, etc.). Well known or can be found in most bacteriological manuals.
BIBLIOGRAPHICAL LIST
Basic
Baltrashevich A.K. et al. Solid medium without blood and its semi-liquid and liquid versions for the cultivation of bacteroids / Scientific Research Laboratory of Experimental Biological Models of the USSR Academy of Medical Sciences. M. 1978 7 p. Bibliography 7 titles Dep. in VNIIMI 7.10.78, No. D. 1823.
Goncharova G.I. On the method of cultivating V. bifidum // Laboratory work. 1968. № 2. P. 100-1 D 2.
Methodological recommendations for the isolation and identification of opportunistic enterobacteria and salmonella in acute intestinal diseases of young farm animals / I. N. Blokhina E., S. Voronin et al. KhM: MBA, 1990. 32 p.
Petrovskaya V. G., Marko O. P. Human microflora in normal and pathological conditions. M.: Medicine, 1976. 221 p.
Chakhava O. V. et al. Microbiological and immunological foundations of gnotobiology. M.: Medicine, 1982. 159 p.
Knothe N. u. a. Vaginales Keimspektrum//FAC: Fortschr. antimlkrob, u. antirieoplastischen Chemotherapie. 1987. Bd. 6-2. S. 233-236.
Koopman Y. P. et al. Associtidn of germ-free rats with different rnicrofloras // Zeitschrift fur Versuchstierkunde. 1984. Bd. 26, N 2. S. 49-55.
Varel V. H. Activity of fiber-degrading microorganisms in the pig large intestine//J. Anim. Science. 1987. V. 65, N 2. P. 488-496.
Additional
Boyd M. E. Postoperative gynecologic infections//Can. J. Surg. 1987.
V. 30,’N 1. P. 7-9.
Masfari A. N., Duerden B, L, Kirighorn G. R. Quantitative studies of vaginal bacteria//Genitourin. Med. 1986. V. 62, N 4. P. 256-263.
Methods for quantitative and qualitative evaluation of vaginal microfiora during menstruation / A. B. Onderdonk, G. A. Zamarchi, Y. A. Walsh et al. //Appl. and Environ. Microbiology. 1936. V. 51, N 2. P. 333-339.
Miller J. M., Pastorek J. G. The microbiology of premature rupture of the membranes//Clin. Obstet. and Gyriecol. 1986. V. 29, N 4. P. 739-757.
The human body normally contains hundreds of species of microorganisms; bacteria dominate among them. Viruses and protozoa are represented by a significantly smaller number of species.
The term “normal microflora” combines microflora that are more or less often isolated from the body of a healthy person.
Blood and internal organs healthy humans and animals are practically sterile. They do not contain germs or cat. cavities in contact with the external environment - the uterus, bladder. Microbes in the lungs are quickly destroyed. But in the mouth. cavities, in the nose, in the intestines, in the vagina there is a constant norm. microflora characteristic of each area of the body (autochthonous). In this case, a person serves as a source of income to the environment. environment of many m-s.
During the prenatal period, the organism develops in the sterile conditions of the uterine cavity, and its primary contamination occurs during passage through the birth canal and on the first day of contact with the environment. Then, over a number of years after birth, a characteristic definition is formed. biotopes of his body microbial “landscape”. Among the norms. microflora distinguishes resident (permanent) obligate microflora and transient (non-permanent) microflora, which is not capable of long-term existence in the body.
Main microbial biotopes
Leather. On the skin covers m-s are susceptible to the action of bactericidal factors in sebaceous secretions that increase acidity. In such conditions, mainly Staphylococcus epidermidis, micrococci, sarcina, aerobic and anaerobic diphtheroids live. Following basic hygiene rules can reduce the number of bacteria by 90%.
Breathe. system. In the upper breath. dust particles loaded with microorganisms enter the pathway, most of which are retained in the nasopharynx and oropharynx. Bacteroides, corynemorphic bacteria, Haemophilus influenzae, lactobacilli, staphylococci, streptococci, non-pathogenic Neisseria, etc. grow here. The trachea and bronchi are usually sterile.
Genitourinary system. Microbial biocenosis of the genitourinary organs. systems are more meager. The upper urinary tract is usually sterile; Staphylococcus epidermidis and diphtheroids dominate in the lower sections; Fungi of the genus Candida are often isolated. Mycobacterium smegmatis dominates in the external sections. The vaginal microbiocenosis includes lactic acid bacteria, enterococci, streptococci, staphylococci, corynebacteria, and Doderline bacilli.
Oral cavity. Mouth. the cavity is a convenient place for the development of tissues. Humidity, abundance of nutrients, optimal temperature, slightly alkaline reaction of the environment. favorable factors for the development of properties. Therefore, the microflora of the oral cavity is extremely abundant and diverse. Streptococci dominate among bacteria, constituting 30-60% of the total microflora of the oropharynx. Less aerated areas are colonized by anaerobes - actinomycetes, bacteroides, fusobacteria and veillonella. The oral cavity is also inhabited by spirochetes, mycoplasmas, fungi of the genus Candida and a variety of protozoa. Normal microflora of the oral cavity can cause inflammatory processes and dental caries, however, with a huge number of microbes in the oral cavity, inflammatory processes occur relatively rarely. The barrier function of the mucous membrane and enamel of teeth and phagocytosis are of protective importance.
Gastrointestinal tract (GIT). Bacteria most actively colonize the gastrointestinal tract. There are practically no microbes in the stomach of a healthy person, which is caused by the action of gastric juice. Nevertheless, certain species (for example, Helicobacter pylori) have adapted to living on the gastric mucosa.
The upper parts of the small intestine are also relatively free of bacteria, which is due to the unfavorable effects of alkaline pH and digestive tract. enzymes. However, candida, streptococci and lactobacilli can be found in these sections.
The lower parts of the small intestine and, especially, the large intestine are a huge reservoir of bacteria; their content can reach 1012 in 1 g of feces (30% of the dry weight of feces). The intestinal microflora is represented by three main groups. Group 1 includes gram-positive. non-spore anaerobes - bifidobacteria and gram-negatives. bacteroids, making up 95% of the microbiocenosis. Group 2 (associated microflora) is represented mainly by aerobes (lactobacteria, coccal flora, Escherichia coli) specific gravity it is small and does not exceed 5%. Group 3 includes rare opportunistic or facultative microflora. Its specific gravity does not exceed 0.01-0.001% of the total number of microbes. Representatives of the facultative microflora are Proteus, Pseudomonas aeruginosa, Staphylococcus, Candida, Serracina, Enterobacteria and Campylobacteria.
Representatives of the 2nd and 3rd groups under physiological conditions are symbionts of the 1st group, they coexist perfectly with it, without causing harm, showing aggressive properties only under certain conditions.
The importance of body microflora for humans.
Barrier. The intestinal parietal microflora colonizes the mucous membrane in the form of microcolonies, forming a kind of biological film. At the same time, bacteria prevent harmful microbes and their metabolic products from entering the body.
Protection. Normal microflora is one of the most important factors natural resistance (stability) of the body, since it exhibits a highly antagonistic effect in relation to others, including pathogenic bacteria, preventing their reproduction in the body.
Metabolism. Microflora, especially the large intestine, is involved in digestive processes, including the metabolism of cholesterol and bile acids. The important role of microflora is also that it provides the human body with various vitamins that are synthesized by its representatives (vitamin B1, B2, B6, B12, K, nicotinic, pantothenic, folic acid, etc.) These vitamins provide most the body's needs for them. Microflora regulates water-salt metabolism and gas composition of the intestine.
Detoxification. Microorganisms inhibit the release of toxins by some microorganisms and take part in the detoxification of those entering from external environment into the body of xenobiotics (foreign substances) and the resulting toxic metabolic products by converting them into non-toxic products, destroying carcinogenic substances.
Stimulation of the immune system. Microflora, with its antigenic factors, stimulates the development of the body's lymphoid tissue, the formation of antibodies and thus helps maintain homeostasis of the mucous membranes.
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