Normal human microflora is a combination of many microbiocenoses. Microbiocenosis is a collection of microorganisms of the same habitat, for example, microbiocenosis of the oral cavity or microbiocenosis of the respiratory tract. Microbiocenoses of the human body are interconnected. The living space of each microbiocenosis is a biotope. The oral cavity, large intestine or respiratory tract are biotopes.

The biotope is characterized by homogeneous conditions for the existence of microorganisms. Thus, biotopes have been formed in the human body, in which a certain microbiocenosis is settled. And any microbiocenosis is not just a certain number of microorganisms, they are interconnected by food chains. In each biotope, there are the following types of normal microflora:

• characteristic of a given biotope or permanent (resident), actively reproducing;
• uncharacteristic for this biotope, temporarily trapped (transient), it does not actively reproduce.

Normal human microflora is formed from the first moment of the birth of a child. Its formation is influenced by the microflora of the mother, the sanitary condition of the room in which the child is located, artificial or natural feeding. The state of normal microflora is also affected by the hormonal background, the acid-base state of the blood, the process of production and release of chemicals by the cells (the so-called secretory function of the body). By the age of three months, a microflora is formed in the child's body, similar to the normal microflora of an adult.

All systems of the human body that are open to contact with the external environment are seeded with microorganisms. Closed for contact with the microflora of the environment (sterile) are blood, cerebrospinal fluid (CSF), articular fluid, pleural fluid, lymph of the thoracic duct and tissues of internal organs: heart, brain, liver, kidneys, spleen, uterus, bladder, lungs.

Normal microflora lines the human mucous membranes. Microbial cells secrete polysaccharides (high molecular weight carbohydrates), the mucous membrane secretes mucin (mucus, protein substances) and a thin biofilm is formed from this mixture, which covers hundreds and thousands of microcolonies of normal flora cells from above.

This film with a thickness of not more than 0.5 mm protects microorganisms from chemical and physical effects. But if the factors of self-defense of microorganisms exceed the compensatory capabilities of the human body, then violations may occur, with the development of pathological conditions and adverse consequences. Such consequences include

• — the formation of antibiotic-resistant strains of microorganisms;
• — formation of new microbial communities and changes in the physicochemical state of biotopes (intestines, skin, etc.);
• - an increase in the spectrum of microorganisms that are involved in infectious processes and an expansion of the spectrum of human pathological conditions;
• - the growth of infections of various localization; the appearance of individuals with congenital and acquired reduced resistance to pathogens of infectious diseases;
• - decrease in the effectiveness of chemotherapy and chemoprophylaxis, hormonal contraceptives.

The total number of microorganisms of normal human flora reaches 10 14, which exceeds the number of cells of all tissues of an adult. The basis of the normal human microflora is anaerobic bacteria (living in an oxygen-free environment). In the intestines, the number of anaerobes is a thousand times greater than the number of aerobes (microorganisms that require oxygen to live).

The meaning and functions of normal microflora:

• - Participates in all types of metabolism.
• - Participates in the destruction and neutralization of toxic substances.
• - Participates in the synthesis of vitamins (groups B, E, H, K).
• - It releases antibacterial substances that suppress the vital activity of pathogenic bacteria that have entered the body. The combination of mechanisms ensures the stability of normal microflora and prevents the colonization of the human body by foreign microorganisms.
• - Makes a significant contribution to the metabolism of carbohydrates, nitrogenous compounds, steroids, water-salt metabolism, and immunity.

Most contaminated by microorganisms

• - skin;
• - oral cavity, nose, pharynx;
• - upper respiratory tract;
• - colon;
• - vagina.

Normally, few microorganisms contain

• - lungs;
• - urinary tract;
• - bile ducts.

How is the normal intestinal microflora formed? First, the mucosa of the gastrointestinal tract is seeded with lactobacilli, clostridia, bifidobacteria, micrococci, staphylococci, enterococci, E. coli and other microorganisms that have accidentally entered it. Bacteria are fixed on the surface of the intestinal villi, in parallel, the process of biofilm formation takes place

As part of the normal human microflora, all groups of microorganisms are detected: bacteria, fungi, protozoa and viruses. Microorganisms of normal human microflora are represented by the following genera:

• - oral cavity - Actinomyces (Actinomycetes), Arachnia (Arachnia), Bacteroides (Bacterioids), Bifidobacterium (Bifidobacteria), Candida (Candida), Centipeda (Centipeda), Eikenella (Eikenella), Eubacteriun (Eubacteria), Fusobacterium (Fusobacteria), Haemophilus (Hemophilus), Lactobacillus (Lactobacillus), Leptotrichia (Leptotrichia), Neisseria (Neisseria), Propionibacterium (Propionibacteria), Selenomonas (Selenomonas), Simonsiella (Simonsiella), Spirochaeia (Spirochea), Streptococcus (Streptococcus), Veillonella (Veillonella), Wolinella (Volinella), Rothia (Rothia);
• - upper respiratory tract - Bacteroides (Bacterioids), Branhamella (Branhamella), Corynebacterium (Corinebacterium), Neisseria (Neisseria), Streptococcus (Streptococci);
• - small intestine - Bifidobacterium (Bifidobacteria), Clostridium (Clostridia), Eubacterium (Eubacteria), Lactobacillus (Lactobacillus), Peptostreptococcus (Peptostreptococcus), Veillonella (Veylonella);
• - large intestine - Acetovibrio (Acetovibrio), Acidaminococcus (Acidaminococcus), Anaerovibrio (Anerovibrio), Bacillus (Bacilli), Bacteroides (Bacterioids), Bifidobacterium (Bifidobacteria), Butyrivibrio (Butyrivibrio), Campylobacter (Campylobacter), Clostridium (Clostridia), Coprococcus (Kopropropococci), Disulfomonas (Disulfomones), Escherichia (Escherichia), Eubacterium (Ebacteria), Fusobacterium (Fuzobacteria), Gemmiger (Hemmiger), Lactobacillus (lactobacteria), Peptoccus (Pepto Kokki), PeptostReptococcus (Peptostosteroptococci), Propionibacterium (Propionibacteria), Roseburia (Roseburia), Selenomonas (Selenomone), Spirochaeta (Spirochete), Succinomonas, Streptococcus (Streptococci), Veillonella (Veylonella), Wolinella (Volinella);
• - skin - Acinetobacter (Acinetobacter), Brevibacterium (Brevibacteria), Corynebacterium (Corinebacteria), Micrococcus (Micrococcus), Propiombacterium (Propionebacterium), Staphylococcus (Staphylococcus), Pityrosponim (Pitirosponim - yeast fungus), Trichophyton (Trichophyton);
• - female genital organs - Bacteroides (Bacterioids), Clostridium (Clostridia), Corynebacterium (Corinebacteria), Eubacterium (Eubacteria), Fusobacterium (Fusobacteria), Lactobacillus (Lactobacillus), Mobiluncus (Mobilunkus), Peptostreptococcus (Peptostreptococcus), Streptococcus (Streptococcus), Spirochaeta (Spirochete), Veillonella (Veylonella).

Under the influence of a number of factors (age, sex, season, food composition, illness, the introduction of antimicrobial substances, etc.), the composition of the microflora can change either within physiological boundaries or beyond them (see Fig.

The human body normally contains hundreds of species of microorganisms; they are dominated by bacteria, viruses and protozoa are represented by a much smaller number of species. The overwhelming majority of such microorganisms are commensal saprophytes; but as in any biocenosis, the relationship in the microorganism-macroorganism system can be both symbiotic and parasitic in nature. The species composition of the microbial biocenosis of various parts of the body periodically changes, but each individual has more or less characteristic microbial communities. According to Lamarck, the main conditions for the survival of a species (including microorganisms) are normal life activity, the rapid reproduction of fertile offspring colonizing a certain habitat. For most commensals, these provisions are not identical to the concepts of "pathogenicity" and "virulence" and are largely determined by the rate of reproduction and colonization. The term "normal microflora" includes microorganisms more or less frequently isolated from the body of a healthy person; bacteria that are part of the normal microflora are presented in table. 6-2. It is often impossible to draw a clear boundary between saprophytes and pathogenic microbes that are part of the normal microflora. The prevailing provisions on the normal microflora are not absolute. For example, meningococci and pneumococci, which cause meningitis, pneumonia and septicemia, are isolated from the nasopharynx by 10% of clinically healthy individuals. For the remaining 90%, they pose a serious danger. In almost every person, such bacteria can sporadically Types Frequency
selections Species Frequency
secretions Skin Sfapby/ococcus aureus Mycobacterium ++ Colon Staphylococcus epidermidis + Staphylococcus aureus + Corynebacterium ++++ Viridescent streptococci ++ Propionibacterium acnes ++++ Group B streptococci + Matassezia furfur ++++ Enterococcus ++ Candida + Lactobacillus ++ +
Oral cavity and nasopharynx Staphylococcus aureus + Actinomyces + S. epidermidis +++ Clostridium ++++ Green streptococci ++++ Pseudomonas + S. pneumoniae ++ Other non-fermenting + Enterococcus + enterobacteria Lactobacillus ++ ++++ Actinomyces Treponema + Peptostra PTOCOCCIS + Candida + Neisseria ++ Mycobacterium +
Vagina Haemophilus influenzae + Haemophilus + Mycoplasma Bacteroides ++ Ureaplasma urealyticum + Porphyromonas ++ S. epidermidis + Prevotella ++ Group B streptococci + Fusobacterium ++++ Viridescent streptococci + Veilonella ++++ Enterococcus + Treponema +++ Lactobacillus +++ + Candida ++ Actinomyces +
Nasal cavity Sfaphyfococcus aureus ++ Peltostreptococcus + $. epidermidis ++++ Clostridium ++ Viridescent streptococci ++ Bifidobacteria + S. pneumoniae + Propionibacterium acnes + Neisseria + Neisseria ± Haemophilus + Acinetobacter +
External ear S. ep/derm/d/s ++++ Enterobacteriaceae + Pseudomonas + Bacteroides + Conjunctiva External genital organs and anterior urethra Staphylococcus aureus + Candida ++ S. epidermidis ++++ Skin microflora (see above) Haemophilus + Mycoplasma + Esophagus and stomach Surviving bacteria from the breath + Ureaplasma urealyticum ± tracts and food masses Small intestine Enterococcus ++ Bacteroides +++ Lactobacillus +++ Peptostreptococcus + Clostridium ++ Mycobacterium ++ Enterobacteria ++ ++++ - isolated almost always; +++ - usually isolated; ++ - often isolated; + - isolated sometimes; ± - isolated relatively rarely.
colonize the nasopharynx; they are designated by the term "transient members of microbial communities". Thus, the entry of a pathogenic microbe into an organ sensitive to its pathogenicity factors does not always lead to the development of the disease. This phenomenon is associated with the state of the protective factors of the macroorganism; Equally important is the participation of microflora that competes with the potential pathogen for food and energy sources and prevents its colonization.
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. In the case of a birth by caesarean section, the composition of microbes that colonize the body of a newborn is significantly different (for example, in the first weeks of life, a deficiency of lactobacilli, enterobacteria, diphtheroids is noted).
Major microbial biotopes
The main parts of the human body inhabited by bacteria: skin, airways, gastrointestinal tract, genitourinary system. In these areas, bacteria live and multiply; and their content varies depending on the conditions of existence. For example, in the stomach, duodenum, bladder, uterus, in the zones of gas exchange in the lungs, there are practically no bacteria in the worm, and their detection gives grounds for suspecting an infectious process. Isolation of bacteria from normally sterile tissues (blood, CSF, synovial fluids, deep tissues) is of diagnostic value. Regardless of their virulent properties, all bacteria are exposed to the protective factors of the host.
Oral cavity
In the oral cavity, microorganisms are affected by saliva, which mechanically washes away bacteria and contains antimicrobial substances (for example, lysozyme). However, there are always areas in the mouth that are easily colonized by microorganisms (eg, gum pockets, gaps between teeth). The composition of the microflora of the oral cavity includes various microorganisms; some form autochthonous microflora, others - allochthonous (inherent in other areas). Autochthonous microflora is typical for this area (in this case, the oral cavity). Among autochthonous microorganisms, resident (obligate) and transient species are distinguished. Among the latter, pathogens of infectious lesions are most often encountered, although commensals living in other biotopes (skin, gastrointestinal tract) also belong to transient species. The allochthonous microflora of the oral cavity is represented by microbes inherent in other areas. It includes species that usually live in the intestines or nasopharynx.
Among the bacteria, streptococci dominate, making up 30-60% of the entire microflora of the oropharynx; different species have developed a certain "geographical specialization", for example, Streptococcus mitior is tropical to the epithelium of the cheeks, Streptococcus salivarius to the papillae of the tongue, Streptococcus sanguis and Streptococcus mutans to the surface of the teeth. Less aerated areas are colonized by anaerobes - actinomycetes, bacteroids, fusobacteria and veillonella. Spirochetes of the genera Leptospira, Borrelia and Treponema, mycoplasmas (M orale, M. salivarium), fungi of the genus Candida and various protozoa (Entamoeba buccalis and E. dentalis, Trichomonas buccalis) also live in the oral cavity. The primary penetration of bacteria into the oral cavity occurs when the fetus passes through the birth canal; the initial microflora is represented by lactobacilli, enterobacteria, corynebacteria, staphylococci and micrococci; already after 2-7 days, this microflora is replaced by bacteria that live in the oral cavity of the mother and the staff of the maternity ward. Inhabitants of the oral cavity have pathogenic potential capable of causing local tissue damage. An important role in the pathogenesis of local lesions is played by organic acids and their metabolites formed during the fermentation of carbohydrates by microorganisms. The main lesions of the oral cavity (dental caries, pulpitis, periodontitis, periodontal diseases, inflammation of soft tissues) cause streptococci, peptostreptococci, actinomycetes, lactobacilli, corynebacteria, etc. Less common anaerobic infections (for example, Berezovsky-Vincent-Plaut disease) cause associations bacteroids, prevotella, actinomycetes, veillonella, lactobacilli, nocardia, spirochetes, etc.
LEATHER
On the skin, microorganisms are subject to the action of bactericidal factors of sebaceous secretion, which increase acidity (accordingly, the pH value decreases). Predominantly Staphylococcus epidermidis, micrococci, sardines, aerobic and anaerobic diphtheroids live in such conditions. Other species - Staphylococcus aureus, a-hemolytic and non-hemolytic streptococci - are more correctly considered as transient. The main areas of colonization are the epidermis (especially the stratum corneum), the skin glands (sebaceous and sweat), and the upper sections of the hair follicles. The microflora of the hairline is identical to the microflora of the skin. The primary colonization of the skin of the fetus occurs during childbirth, but this microflora (actually the flora of the mother's birth canal) is replaced by the above bacteria within a week. Usually 103-104 microorganisms are detected per 1 cm2; in areas with high humidity, their number can reach 106. Compliance with basic hygiene rules can reduce the number of bacteria by 90%.
RESPIRATORY SYSTEM
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 green streptococci, non-pathogenic Neisseria, staphylococci and enterobacteria, meningococci, pyogenic streptococci, pneumococci and whooping cough can be found in the nasopharynx. The upper respiratory tract in newborns is usually sterile and colonizes within 2~3 days. As you grow older, improve your defense mechanisms, the probability of carrying pathogenic bacteria decreases; in adolescents and adults they are relatively rare.
URINARY SYSTEM
Microbial biocenosis of the organs of the genitourinary system is more scarce. The upper urinary tract is usually sterile; in the lower sections dominated by Staphylococcus epidermidis, non-hemolytic streptococci, diphtheroids; fungi of the genera Candida, Torulopsis and Geotrichum are often isolated. Mycobacterium smegmatis dominates in the external sections. Streptococcus agalactiae of group B is isolated from the vagina in 15-20% of pregnant women, which poses a serious danger to newborns in terms of the development of pneumonia and purulent-septic lesions.
gastrointestinal tract
Bacteria colonize the gastrointestinal tract most actively; at the same time, colonization is carried out “by floors”. There are practically no microbes in the stomach of a healthy person, which is caused by the action of gastric juice. However, some species (eg Helicobacter pylori) have adapted to living on the gastric mucosa, but the total number of microorganisms usually does not exceed 103/ml. The upper small intestine is also relatively free of bacteria (less than 103/mL) due to the adverse effects of alkaline pH and digestive enzymes. Nevertheless, candida, streptococci and lactobacilli can be found in these departments. The lower sections of the small intestine, and especially the large intestine, are a huge reservoir of bacteria; their content can reach 1012 per 1 g of feces. The gastrointestinal tract of a newborn can be considered sterile; there is a small number of bacteria that have penetrated during passage through the birth canal. Intensive colonization of the gastrointestinal tract begins during the first day of extrauterine life; in the composition of the microflora, variations are possible in the future. In naturally fed children, Lactobacillus bifidus dominates; other bacteria are E. coli, enterococci, and staphylococci. Formula-fed animals are dominated by Lactobacillus acidophilus, enterobacteria, enterococci and anaerobes (eg clostridia).
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.
INFECTIONS
Most of the infections caused by representatives of the normal microflora are opportunistic in nature. In particular, intestinal anaerobes (eg, bacteroides) can cause abscess formation after penetration into the intestinal wall as a result of trauma or surgery; The main causative agents of frequently recorded post-influenza pneumonia are microorganisms that live in the nasopharynx of any person. The number of such lesions is so great that it seems that doctors are more likely to deal with endogenous rather than exogenous infections, that is, with pathology induced by endogenous microflora. The lack of a clear distinction between opportunistic microbes and commensals suggests that unlimited colonization by any type of bacteria that can survive in the human body can lead to the development of an infectious pathology. But this position is relative - different members of microbial communities exhibit pathogenic properties of a different order (some bacteria cause lesions more often than others). For example, despite the diversity of the intestinal microflora, peritonitis caused by a breakthrough of bacteria into the abdominal cavity is caused by only a few types of bacteria. The leading role in the development of such lesions is played not by the virulence of the pathogen itself, but by the state of the protective systems of the macroorganism; Thus, in persons with immunodeficiency, weakly virulent or avirulent microorganisms (candida, pneumocystis) can cause severe, often fatal lesions.
The normal microflora competes with the pathogenic one; 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 towards 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, a high concentration of these products inhibits the metabolism and release of toxins by pathogenic species (for example, heat-labile toxin by enteropathogenic Escherichia).
STIMULATION OF THE IMMUNE SYSTEM
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 the microflora was established after microbial-free gnotobionts were obtained [from the Greek. gnotos, knowledge, + lat. biota (from Greek bios) life]. It was shown that the normal microflora has a constant antigenic "irritation" of the immune system, and in gnotobionts its absence causes underdevelopment of the main immunocompetent organs (for example, thymus, intestinal lymphoid tissue). Ag representatives of normal microflora cause the formation of antibodies in low titers. They are predominantly represented by IgA, which are released on the surface of the mucous membranes. IgA form the basis of local immunity to penetrating pathogens and prevent commensals from penetrating into deep tissues.
CONTRIBUTION TO METABOLISM
Normal intestinal microflora plays a huge role in the metabolic processes of the body and maintaining their balance.
Providing suction. Metabolism of some substances includes hepatic excretion (in the form of bile) into the intestinal lumen with subsequent return to the liver; a similar hepato-intestinal cycle is characteristic of some sex hormones and bile salts. These products are excreted, as a rule, in the form of glucuronides or sulfates, which are not capable of reabsorption in this form. Absorption is provided by intestinal bacteria that produce glucuronidase and sulfatase. Sulfatases can also have an adverse effect, as established by the example of the artificial sweetener cyclamate. The enzyme converts cyclamate into the carcinogenic product cyclohexamine, which causes malignant degeneration of the bladder epithelium.
Exchange of vitamins and minerals. A generally accepted fact is the leading role of normal microflora in providing the human body with Fe2+, Ca2+ ions, vitamins K, D, group B (especially B, riboflavin), nicotinic, folic and pantothenic acids. 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.
Dysbacteriosis
The composition of microbial communities in body cavities is influenced by various factors: the composition and quality of food, smoking and alcohol consumption, normal peristalsis and timely emptying of the intestines and bladder, the quality of chewing food, and even the nature of
labor activity (sedentary or otherwise). The greatest impact is exerted by diseases associated with changes in the physicochemical properties of epithelial surfaces (for example, malabsorption syndrome), and the use of broad-spectrum antimicrobial drugs that act on any, including non-pathogenic microorganisms. As a result, more resistant species survive - staphylococci, candida and gram-negative rods (enterobacteria, і pseudomonads). The consequence of this is persistent violations of microbial cenoses - dysbacteriosis, or dysbiosis. The most severe forms of dysbiosis are staphylococcal sepsis, sys-! dark candidiasis and pseudomembranous colitis; among all forms, lesions of the intestinal microflora dominate. ]
Indications for bacteriological diagnosis of intestinal dysbacteriosis: long-term infections and disorders in which it is not possible to isolate pathogenic enterobacterins; a protracted period of convalescence after an intestinal infection! tions; dysfunction of the gastrointestinal tract during or after antibiotic therapy or in people who are constantly in contact with antimicrobial drugs. Studies should also be carried out in diseases of malignant growth, in those suffering from dyspeptic disorders, in persons preparing for operations on the abdominal organs, premature or injured newborns, as well as in the presence of bacteremia and purulent processes that are difficult to treat (ulcerative colitis and enterocolitis, pyelitis, cholecystitis and etc.).
Crops are studied for the presence of pathogenic microorganisms and for a violation of the ratio of various types of microbes. The results of the study should be considered objective when analyzing the growth of isolated colonies if the morphology can be studied and the number of colonies per Petri dish can be counted. After identification, the content of microorganisms of each species is recalculated per 1 g of the test material. If pathogenic microflora is detected, it is necessary to study its sensitivity to antibacterial drugs and bacteriophages. When determining susceptibility, narrow-spectrum antibiotics should be preferred for the most targeted pathogen suppression possible.
The evaluation of the results should be approached with caution, since the composition of the intestinal microflora varies. It is necessary to distinguish true dysbacteriosis from dysbacterial reactions (shifts in the composition of the microflora are insignificant or short-term and do not require specific correction). With true dysbacteriosis, microbial cenosis disorders usually correlate with clinical manifestations, and their normalization is quite long (20-30 days). When evaluating the results, the presence or absence of pathogenic microflora should be indicated and the composition of the microorganisms present should be given.
Repeat studies. It should reflect the positive or negative dynamics of changes in the composition of microbial communities.
Correction of dysbiosis. To correct dysbiosis, eubiotics should be used - 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 Escherichia coli, Lactobacillus and Bifidobacterium species, respectively), bifikol (containing Bifidobacterium and Escherichia coli species), bactisubtil (Bacillus subtilis culture) and etc.
ENVIRONMENTAL FACTORS AND MICROORGANISMS
Microorganisms are constantly exposed to environmental factors. The influence of these factors can be favorable or unfavorable. Adverse effects can lead to the death of microorganisms, that is, to have a microbicidal effect (for example, fungi- or virucidal), or to suppress the reproduction of microbes, exerting a static effect (for example, bacteriostatic). The adverse effects of environmental factors on microorganisms have been used by people since ancient times. For example, cellars were often fumigated with sulfur; during epidemics, to disinfect items, they were calcined or treated with special compounds (for example, a mixture of vinegar and wine alcohol). The discovery and study of the properties of pathogenic microorganisms was the beginning of the directed development of methods for suppressing the vital activity of microbes. It was found that some impacts have a selective effect on certain species, others show a wide range of activity.
physical factors
The vital activity of microorganisms is affected by temperature effects, drying, various types of radiation and the osmotic pressure of the external environment.
TEMPERATURE
Microbes adapt to changes in ambient temperature. Allocate the optimal temperature (favorable for growth and reproduction), the minimum and maximum acceptable (beyond their limits, growth stops). In relation to temperature conditions, microorganisms are divided into mesophilic, psychrophilic and thermophilic.
Mesophilic species [from Greek. mesos, medium, intermediate, + phileo, love] grow best within 20-40 ° C; these include most pathogenic and opportunistic microorganisms.
Thermophilic species [from Greek. therm (e), heat, + phileo, love] grow faster at temperatures above 40 ° C, the upper limit is 70 ° C (examples are Thermoactinomyces vulgaris, Bacillus stearothermophilus). Thermotolerant include microbes that grow when the temperature rises to 50 ° C (for example, Methylococcus capsulatus); to extremely thermophilic - species for which the optimal growth temperature exceeds 65 ° C (Sulfolobus). Certain types of bacteria are able to grow at temperatures above 70 ° C: Sulfolobus acidocaldarius grows at 80 ° C, and Pyrodictium occultum (a strict anaerobe that reduces sulfur) at 105 ° C.
Psychrophilic species [from the Greek. psychros, cold, + phileo, love] grow in the temperature range of 0-10 °C; these include the majority of saprophytes living in soil, fresh and sea water (for example, marine luminous bacteria, some iron bacteria of the genus Galionella). High temperature causes coagulation of structural proteins and enzymes of microorganisms. Most vegetative forms die at 60 °C within 30 minutes, and at 80-100 °C - after 1 minute. Low temperatures (for example, below 0 °C), which are harmless to most microbes, are relatively favorable for maintaining viability. Bacteria survive at temperatures below -100 °C; bacterial spores and viruses survive for years in liquid nitrogen. Protozoa and some bacteria (spirochetes, rickettsia and chlamydia) are less resistant to temperature effects.
Sterilization. Temperature effects are used for sterilization - the complete removal of microorganisms from various environments and the disinfection of objects. Many sterilization modes have been developed; it should be remembered that heat treatment is applicable only to heat-resistant materials (glass, metals). The simplest and most accessible methods are calcination and boiling.
Pasteurization. The method makes it possible to effectively destroy microorganisms by incubating the material at 71.7 °C for 15 s, followed by rapid cooling (rapid pasteurization). Slow pasteurization implies a longer exposure (30 min) at 60°C. Strictly speaking, pasteurization is not a sterilizing method, since not all microorganisms are sensitive to it. The method is widely used in the processing of food products for the prevention of intestinal infections, gastrointestinal forms of tuberculosis and Q fever. Dry heat sterilization. It is carried out in dry heat ovens at 160 °C for 2 hours; the method allows you to destroy not only vegetative cells (they die within a few minutes), but also spores of microorganisms (exposure for 2 hours is required). Such impacts destroy the structure of most organic compounds and lead to significant evaporation of liquids (for example, water from nutrient media).
Autoclaving (sterilization with fluid steam) includes treatment with hot steam (121 ° C) under high pressure (1.2-1.5 atm); most effective for sterilization of thermostable liquids. Heat-resistant spores of microorganisms die within 15 minutes. Processing of large volumes (more than 500 ml) requires a longer exposure time. In laboratories, special steam autoclave boilers with horizontal or vertical loading are used. Fluid steam must not be used to sterilize media containing carbohydrates, milk and gelatin.
Tyndalization - a method of fractional sterilization at low temperatures - daily heating of media at 56-58 ° C for 5~6 days. As a result of such fractional heating, vegetative cells of bacteria germinating from heat-resistant spores die. The main disadvantage is the impossibility of complete elimination of microorganisms, since some spores do not have time to germinate in the time intervals between warming sessions, and some; vegetative cells have time to form thermostable spores. The method is used for sterilization of blood serum, ascitic fluid, etc.
DRYING
When the relative humidity of the environment is below 30%, the vital activity of most bacteria stops. The time of their death during drying is different (for example, Vibrio cholerae - in 2 days, and mycobacteria - in 90 days). Therefore, drying is not used as a method of eliminating microbes from substrates. The adverse effect of drying on microorganisms is used in the preservation of dry products and the manufacture of dry food concentrates. Artificial drying of microorganisms, or lyophilization, is widespread. The method involves rapid freezing followed by drying under low pressure (dry sublimation). Freeze drying is used to preserve immunobiological preparations (vaccines, sera), as well as for conservation and long-term preservation of microorganism cultures.
RADIATION
Sunlight has a detrimental effect on microorganisms, with the exception of phototrophic species. At the same time, parasitic species are more sensitive to radiation than saprophytes. The spectrum of solar activity contains non-ionizing (UV and infrared rays) and ionizing (for example, y-rays) radiation. Short-wave UV rays have the greatest microbicidal effect. Radiation energy is used for disinfection, as well as for sterilization of heat-labile materials.
UV rays (primarily short-wave, that is, with a wavelength of 250-270 nm) act on nucleic acids. The microbicidal action is based on the breaking of hydrogen bonds and the formation of thymine dimers in DNA molecules, leading to the appearance of non-viable mutants. The use of UV radiation for sterilization is limited by its low permeability and high absorption activity of water and glass.
X-ray and y-radiation in high doses also causes the death of microbes. Used for sterilization of bacteriological preparations, plastic products. Working with radiation sources requires strict adherence to safety rules. Irradiation causes the formation of free radicals that destroy nucleic acids and proteins, followed by the death of microbial cells.
Microwave radiation is used for rapid re-sterilization of long-term stored media. The sterilizing effect is achieved by a rapid rise in temperature.
OSMOTIC PRESSURE
A high extracellular concentration of sugars and salts leads to the release of water from bacteria and protozoa. This property of concentrated solutions of sugars and table salt is used for food preservation. The sensitivity of microorganisms to such exposure is variable (for example, the causative agent of botulism dies in a 6% NaCl solution, and fungi of the genus Candida in 14%). Substances that increase osmotic pressure do not provide reliable death of all microorganisms; canned food made on their basis cannot be considered safe.
FILTRATION
An effective method for the physical removal of microorganisms is filtration. Natural disinfection of soil water is carried out by filtration through porous rocks that trap microbes. To remove microorganisms, various natural (for example, cellulose, kaolin, diatomaceous earth, asbestos) and artificial (fine-pored glass, porcelain) materials are used; they provide effective elimination of microorganisms from liquids and gases. Microbes are adsorbed on the pore walls of the filter material. Filters are in the form of candles (for example, Chamberlain candles), or plates inserted into filtering devices (Seitz apparatus) or special nozzles. Filtration is used to sterilize temperature-sensitive liquids, to separate microbes and their metabolites (exotoxins, enzymes), and to isolate viruses.
Chemical Factors
The ability of a number of chemicals to suppress the vital activity of microorganisms and prevent damage to organic substrates has been known since ancient times. In particular, the Egyptians widely used acids, alkalis, natural aromatic substances for the mummification of the dead; Persian fire-worshippers used oil and SS products to protect wood and leather from decay. The use of chemicals is the basis of the antiseptic method (proposed by Joseph Lister in 1867). Efficiency depends on the concentration of chemicals and the time of contact with the microbe. Chemical substances can inhibit the growth and reproduction of microorganisms, exhibiting a static effect, or cause their death [microbicidal effect (from Latin caedo, to kill)]. Disinfectants and antiseptics give a nonspecific microbicidal effect; chemotherapeutic agents exhibit selective antimicrobial activity.
DISINFECTANTS AND ANTISEPTICS
Disinfectants are non-specific chemical agents used to treat premises, equipment and various items. Antiseptics are substances used to treat living tissues. Disinfectants have a bactericidal effect in working concentrations, and antiseptics (depending on the concentration) have a bacteriostatic or bactericidal effect. Antiseptics and disinfectants are usually readily soluble in water and act quickly; they are cheap and, when used correctly, do not have a harmful effect on the human body. Disinfection reduces the number of pathogenic microorganisms on environmental objects. Disinfection is carried out with a certain frequency (prophylactic disinfection), or when an infectious disease occurs or is suspected of it (focal disinfection).
Alcohols, or alcohols (ethanol, isopropanol, etc.). As antiseptics, they are most effective in the form of 60-70% aqueous solutions. Alcohols precipitate proteins and wash out lipids from the cell wall. When used correctly, they are effective against vegetative forms of most bacteria; spores of bacteria and fungi, as well as viruses, are resistant to them.
Halogens and halogen-containing preparations (iodine and chlorine preparations) are widely used as disinfectants and antiseptics. The drugs interact with the hydroxyl groups of proteins, disrupting their structure.
As antiseptics, iodine-containing preparations are used - an alcoholic solution of iodine (5% in ethanol); iodinol (1% aqueous solution contains 0.1% iodine, 0.3% potassium iodide and 0.9% polyvinyl alcohol, which slows down the release of iodine); iodonate (an aqueous solution of a complex of a surfactant with iodine); povidone-iodine (a complex of iodine with polyvinylpyrrolidone) and Lugol's solution are used to treat mucous membranes.
As disinfectants, chlorine-containing preparations are used - gaseous chlorine (interacting with water, forms hypochlorous acid; in the presence of organic substances, the antimicrobial effect decreases); bleach (5.25% NaCIO, also forming hypochlorous acid when dissolved); chloramine B (contains 25-29% active chlorine; for the disinfection of drinking water, it is used in the form of tablets containing 3 mg of active chlorine); chlorhexidine digluconate (gibitan).
Aldehydes alkylate sulfhydryl, carboxyl and amino groups of proteins and other organic compounds, causing the death of microorganisms. Aldehydes are widely used as preservatives. The most famous - formaldehyde (8%) and glutaraldehyde (2-2.5%) - exhibit an irritating effect (especially vapors), limiting their widespread use.
Formaldehyde solution has disinfectant and deodorizing effects. It is used for washing hands, disinfecting instruments, treating the skin of the legs with excessive sweating. Included in the preparations (formidron, formalin ointment). A soap solution of formaldehyde (lysoform) is used for douching in gynecological practice, for disinfecting hands and premises.
Urotropin (hexamethylenetetramine) in the acidic environment of the body breaks down with the release of formaldehyde; the latter, excreted in the urine, has an antiseptic effect. Used for infectious processes of the urinary and biliary tract, skin diseases. Included in the combined preparations (calcex, urobesal).
5-5819
Cyminal, cimisol and cidipol are antiseptics that act due to the formation of formaldehyde by hydrolysis; used for individual prevention of sexually transmitted diseases in men after casual sex.
Acids and alkalis are used as antiseptics. Among the most famous acids are boric, benzoic, acetic and salicylic. Used to treat lesions caused by pathogenic fungi and bacteria. The most common salicylic acid is used in alcohol solutions (1-2%), powders, ointments, pastes (for example, for the treatment of dermatomycosis in areas subject to friction); It also has, depending on the concentration, a distracting, irritating and xratolitic effect. Of the alkalis, the most common solution is ammonia (ammonia contains 9.5-10.5% ammonia), used to treat the surgeon's hands (0.5% solution).
Metals. The antimicrobial effect is based on the ability to precipitate proteins and other organic compounds. Silver nitrate (lapis), copper sulfate (copper sulfate) and mercury chromate (merbromin) are widely used as antiseptics. Metal compounds (especially lead, arsenic and mercury) are not recommended for disinfection and antiseptics, since they can accumulate in the human body. The exception is sublimate (mercury dichloride), sometimes used to disinfect linen, clothing, and patient care items.
Phenols and their substituted derivatives are widely used as disinfectants, and in lower concentrations as antiseptics. The drugs denature proteins and disrupt the structure of the cell wall. The use of phenol itself was abandoned long ago due to its toxicity, but its derivatives (for example, hexachlorophene, resorcinol, chlorophene, thymol, salol) are often used.
Cationic detergents have a bactericidal effect associated with a change in the permeability of the CPM. Their effect is reduced by anionic surfactants (for this reason, cationic detergents are incompatible with soaps), low pH values ​​​​(i.e. increased acidity), some organic compounds, metal ions. Cationic detergents are adsorbed by porous and fibrous materials. When applied to the skin, they form a film under which live microorganisms can remain. Most often used to treat the surgeon's hands (drugs tsirigel, degmicide, rokkal).
Gases as disinfectants have been known since ancient times. Sulfur dioxide was widely used in antiquity for the treatment of warehouses and the preservation of food products. Deratization with sulfur dioxide is no less widespread. For the destruction of spores of microorganisms during the sterilization of plastic items, ethylene and propylene oxides are used under pressure at 30-60 ° C. The method allows you to effectively destroy most microorganisms, including those in tissues and fluids (blood, purulent discharge). The mechanism of action is associated with the ability of ethylene oxide to alkylate proteins. In particular, sulfhydryl groups of vegetative forms and carboxyl groups of spore coats are damaged.
Dyes. Various dyes have long been used as antiseptics (for example, brilliant green, methylene blue, rivanol, basic fuchsin).
Oxidizers. The mechanism of antimicrobial activity is associated with the oxidation of metabolites and enzymes of microorganisms, or the denaturation of microbial proteins. The most common oxidizing agents used as antiseptics are hydrogen peroxide and potassium permanganate (colloquially, potassium permanganate).
CHEMOTHERAPEUTICS
Substances with a selective action are used as chemotherapeutic agents.
They must be effective in inhibiting or destroying pathogens (see Chapter 9),
while not having a toxic effect on the body.
GGIRPP

This textbook is intended for students of medical universities, students of medical colleges, as well as applicants. It contains information about the ultrastructure and physiology of bacteria, discusses issues of immunology and virology, describes in detail the structure and morphology of pathogens of various infections, and pays attention to the basics of medical biotechnology and genetic engineering.

Topic 6. Normal microflora of the human body

1. Normal human microflora

The human body and the microorganisms inhabiting it are a single ecosystem. The surfaces of the skin and mucous membranes of the human body are abundantly populated by bacteria. At the same time, the number of bacteria inhabiting the integumentary tissues (skin, mucous membranes) is many times greater than the number of the host's own cells. The quantitative fluctuations of bacteria in the biocenosis can reach several orders of magnitude for some bacteria and, nevertheless, fit into the accepted standards.

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

In the human body, in accordance with the living conditions, biotopes with certain microbiocenoses are formed. Any microbiocenosis is a community of microorganisms that exists as a whole, connected by food chains and microecology.

Types of normal microflora:

1) resident- constant, typical for this species. The number of characteristic species is relatively small and relatively stable, although numerically they are always represented most abundantly. Resident microflora is found in certain places of the human body, while an important factor is its age;

2) transient- temporarily caught, not typical for this biotope; it does not actively reproduce, therefore, although the species composition of transient microorganisms is diverse, they are not numerous. A characteristic feature of this type of microflora is that, as a rule, getting on the skin or mucous membranes from the environment, it does not cause diseases and does not live permanently on the surfaces of the human body. It is represented by saprophytic opportunistic microorganisms that live on the skin or mucous membranes for several hours, days or weeks. The presence of transient microflora is determined not only by the intake of microorganisms from the environment, but also by the state of the immune system of the host organism, the composition of the permanent normal microflora. The composition of the transient microflora is not constant and depends on age, environment, working conditions, diet, previous diseases, injuries and stressful situations.

Normal microflora is formed from birth, and at this time, its formation is influenced by the microflora of the mother and the nosocomial environment, the nature of feeding. Bacterial colonization of the body continues throughout its life. At the same time, the qualitative and quantitative composition of normal microflora is regulated by complex antagonistic and synergistic relationships between its individual representatives in the composition of biocenoses. Microbial contamination is typical for all systems that have contact with the environment. Nevertheless, normally, many tissues and organs of a healthy person are sterile, in particular, blood, cerebrospinal fluid, articular fluid, pleural fluid, thoracic duct lymph, internal organs: heart, brain, liver parenchyma, kidneys, spleen, uterus, bladder, lung alveoli . Sterility in this case is provided by non-specific cellular and humoral immunity factors that prevent the penetration of microbes into these tissues and organs.

On all open surfaces and in all open cavities, a relatively stable microflora is formed, specific for a given organ, biotype, or its site.

The highest contamination is characterized by:

1) colon. The normal microflora is dominated by anaerobic bacteria (96–99%) (bacteroids, anaerobic lactic acid bacteria, clostridia, anaerobic streptococci, fusobacteria, eubacteria, veillonella), aerobic and facultative anaerobic bacteria (1–4%) (gram-negative coliform bacteria - intestinal coli, enterococci, staphylococci, proteus, pseudomonads, lactobacilli, fungi of the genus Candida, certain types of spirochetes, mycobacteria, mycoplasmas, protozoa and viruses);

2) oral cavity. The normal microflora of different parts of the oral cavity is different and is determined by the biological characteristics of the species living here. Representatives of the microflora of the oral cavity are divided into three categories:

a) streptococci, neisseria, veillonella;

b) staphylococci, lactobacilli, filamentous bacteria;

c) yeast-like fungi;

3) urinary system. The normal microflora of the outer part of the urethra in men and women is represented by corynebacteria, mycobacteria, gram-negative bacteria of fecal origin and non-spore-forming anaerobes (these are peptococci, peptostreptococci, bacteroids). On the external genitalia in men and women, mycobacteria smegma, staphylococcus, mycoplasma and saprophytic treponema are localized;

4) upper respiratory tract. The native microflora of the nose consists of corynebacteria, Neisseria, coagulase-negative staphylococci and α-hemolytic streptococci; S. aureus, E. coli, β-hemolytic streptococci may be present as transient species. The microflora of the pharynx is more diverse due to the mixing of the microflora of the oral cavity and the airways and consists of: Neisseria, diphtheroids, α- and β-hemolytic streptococci, enterococci, mycoplasmas, coagulase-negative staphylococci, moraxella, bacteroids, borrelia, treponema and actinomycetes. Streptococci and Neisseria predominate in the upper respiratory tract, staphylococci, diphtheroids, hemophilic bacteria, pneumococci, mycoplasmas, bacteroids are found;

5) leather, especially her hairy part. In connection with constant contact with the external environment, the skin is a habitat for transient microorganisms, while having a constant microflora, the composition of which is different in different anatomical zones and depends on the oxygen content in the environment surrounding the bacteria, as well as on proximity to the mucous membranes, secretion features and other factors. factors. The composition of the resident microflora of the skin and mucous membranes is characterized by the presence of Staphylococcus epidermidis, S. aureus, Micrococcus spp., Sarcinia spp., Propionibacterium spp., coryneform bacteria. Transient microflora includes: Streptococcus spp., Peptococcus cpp., Bacillus subtilis, Escherichia coli, Enterobacter spp., Acinebacter spp., Moraxella spp., Pseudomonadaceae, Lactobacillus spp., Nocardiodes spp., aspergillus spp., Candida albaicans.

The microorganisms that make up the normal microflora are a clear morphological structure in the form of a biofilm - a polysaccharide framework consisting of polysaccharides of microbial cells and mucin. It contains microcolonies of cells of normal microflora. The biofilm thickness is 0.1–0.5 mm. It contains from several hundred to several thousand microcolonies formed from both anaerobic and aerobic bacteria, the ratio of which in most biocenoses is 10:1–100:1.

Biofilm formation creates additional protection for bacteria. Inside the biofilm, bacteria are more resistant to chemical and physical factors.

Factors affecting the state of normal microflora:

1) endogenous:

a) the secretory function of the body;

b) hormonal background;

c) acid-base state;

2) exogenous: living conditions (climatic, domestic, environmental).

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

1) accidental mucosal seeding. Lactobacilli, clostridia, bifidobacteria, micrococci, staphylococci, enterococci, Escherichia coli, etc. enter the gastrointestinal tract;

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

2. Main functions of normal microflora

The normal microflora is considered as an independent extracorporeal organ with a specific anatomical structure and the following functions.

1. Antagonistic function. Normal microflora provides colonization resistance, i.e., the resistance of the corresponding parts of the body (epitopes) to colonization by random, including pathogenic, microflora. This stability is ensured both by the release of substances that have a bactericidal and bacteriostatic effect, and by the competition of bacteria for nutrient substrates and ecological niches.

2. Immunogenic function. Bacteria, which are representatives of the normal microflora, constantly maintain the immune system in good condition with their antigens.

3. Digestive function. Normal microflora takes part in abdominal digestion due to its enzymes.

4. metabolic function. Normal microflora is involved in the metabolism of proteins, lipids, urates, oxalates, steroid hormones, cholesterol due to its enzymes.

5. Vitamin-forming function. As you know, in the process of metabolism, individual representatives of the normal microflora form vitamins. So, the bacteria of the large intestine synthesize biotin, riboflavin, pantothenic acid, vitamins K, E, B 2, folic acid, which are not absorbed in the large intestine, so you should rely only on those that are formed in small quantities in the ileum.

6. Detoxification function. Normal microflora is able to neutralize toxic metabolic products formed in the body or organisms that have entered from the external environment by biosorption or transformation into non-toxic compounds.

7. Regulatory function. Normal microflora is involved in the regulation of gas, water-salt metabolism, maintaining the pH of the environment.

8. genetic function. The normal microflora in this case is an unlimited bank of genetic material, since the exchange of genetic material is constantly taking place both between the representatives of the normal microflora themselves and pathogenic species that fall into one or another ecological niche.

At the same time, the normal intestinal microflora plays an important role in the conversion of bile pigments and bile acids, the absorption of nutrients and their breakdown products. Its representatives produce ammonia and other products that can be adsorbed and participate in the development of hepatic coma.

3. Dysbacteriosis

Dysbacteriosis (dysbiosis)- these are any quantitative or qualitative changes in the normal human microflora typical for a given biotope, resulting from the impact on a macro- or microorganism of various adverse factors.

Microbiological indicators of dysbiosis are:

1) decrease in the number of one or more permanent species;

2) the loss of certain traits by bacteria or the acquisition of new ones;

3) increase in the number of transient species;

4) the emergence of new species not characteristic of this biotope;

5) weakening of the antagonistic activity of normal microflora.

The reasons for the development of dysbacteriosis can be:

1) antibiotic and chemotherapy;

2) severe infections;

3) severe somatic diseases;

4) hormone therapy;

5) radiation exposure;

6) toxic factors;

7) deficiency of vitamins.

Dysbacteriosis of different biotopes has different clinical manifestations. Intestinal dysbacteriosis can manifest itself in the form of diarrhea, nonspecific colitis, duodenitis, gastroenteritis, chronic constipation. Respiratory dysbacteriosis occurs in the form of bronchitis, bronchiolitis, chronic lung diseases. The main manifestations of oral dysbiosis are gingivitis, stomatitis, caries. Dysbacteriosis of the reproductive system in women proceeds as vaginosis.

Depending on the severity of these manifestations, several phases of dysbacteriosis are distinguished:

1) compensated, when dysbacteriosis is not accompanied by any clinical manifestations;

2) subcompensated, when local inflammatory changes occur as a result of an imbalance in the normal microflora;

3) decompensated, in which the process is generalized with the appearance of metastatic inflammatory foci.

Laboratory diagnosis of dysbacteriosis

The main method is bacteriological examination. At the same time, quantitative indicators prevail in the evaluation of its results. Not specific identification is carried out, but only to the genus.

An additional method is chromatography of the spectrum of fatty acids in the material under study. Each genus has its own spectrum of fatty acids.

Correction of dysbacteriosis:

1) elimination of the cause that caused the imbalance of normal microflora;

2) the use of eubiotics and probiotics.

Eubiotics- these are preparations containing live bactericinogenic strains of normal microflora (colibacterin, bifidumbacterin, bifikol, etc.).

Probiotics- These are substances of non-microbial origin and food products containing additives that stimulate their own normal microflora. Stimulants - oligosaccharides, casein hydrolyzate, mucin, whey, lactoferrin, dietary fiber.

MAIN FUNCTIONS OF THE NORMAL MICROFLORA OF THE INTESTINAL TRACT

Normal microflora (normoflora) of the gastrointestinal tract is a necessary condition for the life of the body. The microflora of the gastrointestinal tract in the modern sense is considered as the human microbiome...

normoflora(microflora in a normal state) orThe normal state of the microflora (eubiosis) - is qualitative and quantitativethe ratio of various populations of microbes of individual organs and systems that maintains the biochemical, metabolic and immunological balance necessary to maintain human health.The most important function of the microflora is its participation in the formation of the body's resistance to various diseases and the prevention of colonization of the human body by foreign microorganisms.

In any microbiocenosis, including intestinal, there are always permanently inhabiting species of microorganisms - 90% related to the so-called. obligate microflora ( synonyms: main, autochthonous, indigenous, resident, obligatory microflora), which plays a leading role in maintaining symbiotic relationships between the macroorganism and its microbiota, as well as in the regulation of intermicrobial relations, and there are also additional (associated or facultative microflora) - about 10% and transient ( random species, allochthonous, residual microflora) - 0.01%

Those. the entire intestinal microflora is subdivided into:

• obligate - home orobligatory microflora , about 90% of the total number of microorganisms. The composition of the obligate microflora mainly includes anaerobic saccharolytic bacteria: bifidobacteria (Bifidobacterium), propionic acid bacteria (Propionibacterium), bacteroids (Bacteroides), lactobacilli (Lactobacillus);
• - concomitant oradditional microflora, accounts for about 10% of the total number of microorganisms. Optional representatives of the biocenosis: Escherichia ( coli and - Escherichia), enterococci (Enterococcus), fusobacteria (Fusobacterium), peptostreptococci (Peptostreptococcus), clostridia (Clostridium) eubacteria (Eubacterium) and others, of course, have a number of physiological functions that are important for the biotope and the organism as a whole. However, their predominant part is represented by conditionally pathogenic species, which, with a pathological increase in populations, can cause serious complications of an infectious nature.
• residual - transient microflora or random microorganisms, less than 1% of the total number of microorganisms. The residual microflora is represented by various saprophytes (staphylococci, bacilli, yeast fungi) and other opportunistic representatives of enterobacteria, which include intestinal: Klebsiella, Proteus, Citrobacter, Enterobacter, etc.Transient microflora (Citrobacter, Enterobacter, Proteus, Klebsiella, Morganella, Serratia, Hafnia, Kluyvera, Staphylococcus, Pseudomonas, Bacillus, yeast and yeast-like fungi, etc.), mainly consists of individuals brought from outside. Among them, there may be variants with a high aggressive potential, which, when the protective functions of the obligate microflora are weakened, can increase populations and cause the development of pathological processes.

There is little microflora in the stomach, much more in the small intestine and especially in the large intestine. It is worth noting that suction fat-soluble substances, the most important vitamins and trace elements occurs mainly in the jejunum. Therefore, the systematic inclusion in the diet of probiotic products and dietary supplements, whichcontain microorganisms that regulate the processes of intestinal absorption,becomes a very effective tool in the prevention and treatment of alimentary diseases.

Intestinal absorption- this is the process of the entry of various compounds through a layer of cells into the blood and lymph, as a result of which the body receives all the substances it needs.

The most intensive absorption occurs in the small intestine. Due to the fact that small arteries branching into capillaries penetrate into each intestinal villus, the absorbed nutrients easily penetrate into the liquid media of the body. Glucose and proteins broken down to amino acids are absorbed into the blood only moderately. Blood carrying glucose and amino acids is sent to the liver where carbohydrates are deposited. Fatty acids and glycerin - a product of the processing of fats under the influence of bile - are absorbed into the lymph and from there enter the circulatory system.

The picture on the left(diagram of the structure of the villi of the small intestine): 1 - cylindrical epithelium, 2 - central lymphatic vessel, 3 - capillary network, 4 - mucous membrane, 5 - submucosal membrane, 6 - muscular plate of the mucous membrane, 7 - intestinal gland, 8 - lymphatic channel .

One of the meanings of microflora large intestine is that it is involved in the final decomposition of the remnants of undigested food.In the large intestine, digestion ends with the hydrolysis of undigested food residues. During hydrolysis in the large intestine, enzymes that come from the small intestine and enzymes from intestinal bacteria are involved. There is an absorption of water, mineral salts (electrolytes), the breakdown of plant fiber, the formation of feces.

Microflora plays a significant (!) role inperistalsis, secretion, absorption and cellular composition of the intestine. The microflora is involved in the decomposition of enzymes and other biologically active substances. Normal microflora provides colonization resistance - protection of the intestinal mucosa from pathogenic bacteria, suppressing pathogenic microorganisms and preventing infection of the body.Bacterial enzymes break down undigested in the small intestine. The intestinal flora synthesizes vitamin K and B vitamins, a number of irreplaceable amino acids and enzymes needed by the body.With the participation of microflora in the body, there is an exchange of proteins, fats, carbons, bile and fatty acids, cholesterol, procarcinogens (substances that can cause cancer) are inactivated, excess food is disposed of and feces are formed. The role of normoflora is extremely important for the host organism, which is why its violation ( dysbacteriosis) and the development of dysbiosis in general leads to serious metabolic and immunological diseases.

The composition of microorganisms in certain parts of the intestine depends on many factors: lifestyle, nutrition, viral and bacterial infections, and medications, especially antibiotics. Many diseases of the gastrointestinal tract, including inflammatory diseases, can also disrupt the intestinal ecosystem. The result of this imbalance is common digestive problems: bloating, indigestion, constipation or diarrhea, etc.

To learn more about the role of the gut microbiome in maintaining gastrointestinal health, see the article:

See additionally:

The gut microflora (gut microbiome) is an extraordinarily complex ecosystem. One individual has at least 17 bacterial families, 50 genera, 400-500 species, and an indeterminate number of subspecies. The intestinal microflora is divided into obligate (microorganisms that are constantly part of the normal flora and play an important role in metabolism and anti-infective protection) and facultative (microorganisms that are often found in healthy people, but are conditionally pathogenic, i.e. capable of causing diseases with a decrease in microorganism resistance). The dominant representatives of the obligate microflora are bifidobacteria.

Table 1 shows the most famousfunctions of the intestinal microflora (microbiota), while its functionality is much wider and is still being studied

Table 1 Main functions of the gut microbiota
Main functions	Description
Digestion
Protective functions	Synthesis of immunoglobulin A and interferons by colonocytes, phagocytic activity of monocytes, proliferation of plasma cells, formation of intestinal colonization resistance, stimulation of the development of the intestinal lymphoid apparatus in newborns, etc.
Synthetic function	Group K (participates in the synthesis of blood coagulation factors); B 1 (catalyses the reaction of decarboxylation of keto acids, is a carrier of aldehyde groups); В 2 (electron carrier with NADH); B 3 (electron transfer to O 2); B 5 (precursor of coenzyme A, involved in lipid metabolism); В 6 (carrier of amino groups in reactions involving amino acids); В 12 (participation in the synthesis of deoxyribose and nucleotides);
Detoxification function	including neutralization of certain types of drugs and xenobiotics: acetaminophen, nitrogen-containing substances, bilirubin, cholesterol, etc.
Regulatory function	Regulation of the immune, endocrine and nervous systems (the latter - through the so-called " gut-brain-axis» - It is difficult to overestimate the importance of microflora for the body. Thanks to the achievements of modern science, it is known that the normal intestinal microflora takes part in the breakdown of proteins, fats and carbohydrates, creates conditions for the optimal flow of digestion and absorption in the intestine, takes part in the maturation of immune system cells, which enhances the protective properties of the body, etc. .The two main functions of the normal microflora are: barrier against pathogenic agents and stimulation of the immune response: BARRIER ACTION. The intestinal microflora has suppressive effect on the reproduction of pathogenic bacteria and thus prevents pathogenic infections. Processattachments microorganisms to epithelial cellsIya includes complex mechanisms.Bacteria of the intestinal microbiota inhibit or reduce adherence of pathogenic agents by competitive exclusion. For example, bacteria of the parietal (mucosal) microflora occupy certain receptors on the surface of epithelial cells. Pathogenic bacteria, which could bind to the same receptors, are eliminated from the intestine. Thus, intestinal bacteria prevent the penetration of pathogenic and opportunistic microbes into the mucous membrane.(especially propionic acid bacteria) P. freudenreichii have fairly good adhesive properties and attach very securely to the intestinal cells, creating the said protective barrier.Also, bacteria of a constant microflora help maintain intestinal motility and the integrity of the intestinal mucosa. Yes, bactors - commensals of the large intestine during the catabolism of indigestible carbohydrates in the small intestine (the so-called dietary fiber) form short chain fatty acids (SCFA, short-chain fatty acids), such as acetate, propionate, and butyrate, which support barrier functions of the mucin layer mucus (increase the production of mucins and the protective function of the epithelium). IMMUNE SYSTEM OF THE INTESTINE. More than 70% of immune cells are concentrated in the human intestine. The main function of the intestinal immune system is to protect against the penetration of bacteria into the blood. The second function is the elimination of pathogens (pathogenic bacteria). This is provided by two mechanisms: congenital (inherited by the child from the mother, people from birth have antibodies in the blood) and acquired immunity (appears after foreign proteins enter the blood, for example, after suffering an infectious disease). Upon contact with pathogens, the body's immune defenses are stimulated. When interacting with Toll-like receptors, the synthesis of various types of cytokines is triggered. The intestinal microflora affects specific accumulations of lymphoid tissue. This stimulates the cellular and humoral immune response. Cells of the intestinal immune system actively produce secretory immunolobulin A (LgA) - a protein that is involved in local immunity and is the most important marker of the immune response. ANTIBIOTIC-LIKE SUBSTANCES. Also, the intestinal microflora produces many antimicrobial substances that inhibit the reproduction and growth of pathogenic bacteria. With dysbiotic disorders in the intestine, there is not only an excessive growth of pathogenic microbes, but also a general decrease in the body's immune defenses.Normal intestinal microflora plays a particularly important role in the life of the body of newborns and children. Thanks to the production of lysozyme, hydrogen peroxide, lactic, acetic, propionic, butyric and a number of other organic acids and metabolites that reduce the acidity (pH) of the environment, bacteria of normal microflora effectively fight pathogens. In this competitive struggle of microorganisms for survival, antibiotic-like substances such as bacteriocins and microcins occupy a leading place. Below picture Left: Colony of acidophilus bacillus (x 1100), On right: Destruction of Shigella flexneri (a) (Shigella Flexner - a type of bacteria that causes dysentery) under the action of bacteriocin-producing cells of acidophilus bacillus (x 60,000) It should be noted that almost all microorganisms in the intestinehave a special form of coexistence called a biofilm. Biofilm iscommunity (colony)microorganisms located on any surface, the cells of which are attached to each other. Usually, cells are immersed in the extracellular polymeric substance secreted by them - mucus. It is the biofilm that performs the main barrier function from the penetration of pathogens into the blood, by eliminating the possibility of their penetration to epithelial cells. For more information about biofilm, see: HISTORY OF STUDYING THE COMPOSITION OF THE GIT MICROFLORA The history of the study of the composition of the microflora of the gastrointestinal tract (GIT) began in 1681, when the Dutch researcher Anthony van Leeuwenhoek first reported his observations on bacteria and other microorganisms found in human feces and put forward a hypothesis about the coexistence of different types of bacteria in the gastrointestinal tract. -intestinal tract. In 1850, Louis Pasteur developed the concept of functional the role of bacteria in the fermentation process, and the German physician Robert Koch continued research in this direction and created a method for isolating pure cultures, which makes it possible to identify specific bacterial strains, which is necessary to distinguish between pathogenic and beneficial microorganisms. In 1886, one of the founders of the doctrine of intestinal infections F. Escherich first described intestinal coli (Bacterium coli communae). Ilya Ilyich Mechnikov in 1888, working at the Louis Pasteur Institute, argued that in intestines a complex of microorganisms inhabits the human body, which have an “autointoxication effect” on the body, believing that the introduction of “healthy” bacteria into the gastrointestinal tract can modify the effect intestinal microflora and counteract intoxication. The practical implementation of Mechnikov's ideas was the use of acidophilic lactobacilli for therapeutic purposes, which began in the USA in 1920-1922. Domestic researchers began to study this issue only in the 50s of the XX century. In 1955 Peretz L.G. showed that intestinal coli of healthy people is one of the main representatives of the normal microflora and plays a positive role due to its strong antagonistic properties against pathogenic microbes. Started over 300 years ago, studies of the composition of the intestinal microbiocenosis, its normal and pathological physiology and the development of ways to positively influence the intestinal microflora continue to this day. HUMAN AS A BACTERIA HABITAT The main biotopes are: gastrointestinaltract(oral cavity, stomach, small intestine, large intestine), skin, respiratory tract, urogenital system. But the main interest for us here are the organs of the digestive system, because. the bulk of various microorganisms lives there. The microflora of the gastrointestinal tract is the most representative, the mass of intestinal microflora in an adult is more than 2.5 kg, with a population of up to 10 14 CFU / g. It was previously believed that the microbiocenosis of the gastrointestinal tract includes 17 families, 45 genera, more than 500 species of microorganisms (the latest data is about 1500 species) constantly being adjusted. Taking into account new data obtained in the study of the microflora of various biotopes of the gastrointestinal tract using molecular genetic methods and the method of gas-liquid chromatography-mass spectrometry, the total genome of bacteria in the gastrointestinal tract has 400 thousand genes, which is 12 times the size of the human genome. exposed analysis on the homology of the sequenced 16S rRNA genes of the parietal (mucosal) microflora of 400 different sections of the gastrointestinal tract, obtained by endoscopic examination of various sections of the intestines of volunteers. As a result of the study, it was shown that the parietal and luminal microflora includes 395 phylogenetically isolated groups of microorganisms, of which 244 are absolutely new. At the same time, 80% of the new taxa identified in the molecular genetic study belong to non-cultivated microorganisms. Most of the proposed new phylotypes of microorganisms are representatives of the genera Firmicutes and Bacteroides. The total number of species is close to 1500 and requires further clarification. The gastrointestinal tract through the system of sphincters communicates with the external environment of the world around us and at the same time through the intestinal wall - with the internal environment of the body. Due to this feature, the gastrointestinal tract has created its own environment, which can be divided into two separate niches: chyme and mucous membrane. The human digestive system interacts with various bacteria, which can be referred to as "endotrophic microflora of the human intestinal biotope". Human endotrophic microflora is divided into three main groups. The first group includes useful for humans eubiotic indigenous or eubiotic transient microflora; to the second - neutral microorganisms, constantly or periodically sown from the intestine, but not affecting human life; to the third - pathogenic or potentially pathogenic bacteria ("aggressive populations"). Cavity and wall microbiotopes of the gastrointestinal tract In microecological terms, the gastrointestinal biotope can be divided into tiers (oral cavity, stomach, intestines) and microbiotopes (cavitary, parietal and epithelial). The ability to apply in the parietal microbiotope, i.e. histadhesiveness (the ability to fix and colonize tissues) determines the essence of transient or indigenous bacteria. These signs, as well as belonging to a eubiotic or aggressive group, are the main criteria characterizing a microorganism interacting with the gastrointestinal tract. Eubiotic bacteria are involved in the creation of colonization resistance of the organism, which is a unique mechanism of the system of anti-infective barriers. Cavitary microbiotope throughout the gastrointestinal tract is heterogeneous, its properties are determined by the composition and quality of the contents of a particular tier. Tiers have their own anatomical and functional features, so their content differs in the composition of substances, consistency, pH, speed of movement and other properties. These properties determine the qualitative and quantitative composition of cavity microbial populations adapted to them. Parietal microbiotope is the most important structure that limits the internal environment of the body from the external one. It is represented by mucous overlays (mucous gel, mucin gel), glycocalyx located above the apical membrane of enterocytes and the surface of the apical membrane itself. The parietal microbiotope is of the greatest (!) interest from the point of view of bacteriology, since it is in it that interaction with bacteria that is beneficial or harmful to humans occurs - what we call symbiosis. It should be noted that in the intestinal microflora there are 2 types: mucosal (M) flora- mucosal microflora interacts with the mucous membrane of the gastrointestinal tract, forming a microbial-tissue complex - microcolonies of bacteria and their metabolites, epithelial cells, goblet cell mucin, fibroblasts, immune cells of Peyer's plaques, phagocytes, leukocytes, lymphocytes, neuroendocrine cells; translucent (P) flora- luminal microflora is located in the lumen of the gastrointestinal tract, does not interact with the mucous membrane. The substrate for its life is indigestible dietary fiber, on which it is fixed. To date, it is known that the microflora of the intestinal mucosa differs significantly from the microflora of the intestinal lumen and feces. Although each adult has a specific combination of predominant bacterial species in the gut, the composition of the microflora can change with lifestyle, diet, and age. A comparative study of the microflora in adults who are genetically related to one degree or another revealed that genetic factors influence the composition of the intestinal microflora more than nutrition. Figure Note: FOG - fundus of the stomach, AOG - antrum of the stomach, duodenum - duodenum (:Chernin V.V., Bondarenko V.M., Parfenov A.I. Participation of the luminal and mucosal microbiota of the human intestine in symbiotic digestion. Bulletin of the Orenburg Scientific Center of the Ural Branch of the Russian Academy of Sciences (electronic journal), 2013, No. 4) The location of the mucosal microflora corresponds to the degree of its anaerobiosis: obligate anaerobes (bifidobacteria, bacteroids, propionic acid bacteria, etc.) occupy a niche in direct contact with the epithelium, followed by aerotolerant anaerobes (lactobacilli, etc.), even higher - facultative anaerobes, and then - aerobes .Translucent microflora is the most variable and sensitive to various exogenous influences. Changes in diets, environmental impacts, drug therapy, primarily affect the quality of the translucent microflora. See additionally: The number of microorganisms of mucosal and luminal microflora The mucosal microflora is more resistant to external influences than the luminal microflora. The relationship between mucosal and luminal microflora is dynamic and determined by the following factors: endogenous factors - the influence of the mucous membrane of the digestive canal, its secrets, motility and the microorganisms themselves; exogenous factors - influence directly and indirectly through endogenous factors, for example, the intake of a particular food changes the secretory and motor activity of the digestive tract, which transforms its microflora MICROFLORA OF THE MOUTH, ESOPHAGUS AND STOMACH Consider the composition of the normal microflora of different parts of the gastrointestinal tract. The oral cavity and pharynx carry out preliminary mechanical and chemical processing of food and assess the bacteriological hazard with respect to bacteria penetrating the human body. Saliva is the first digestive fluid that processes food substances and affects the penetrating microflora. The total content of bacteria in saliva is variable and averages 108 MK/ml. The composition of the normal microflora of the oral cavity includes streptococci, staphylococci, lactobacilli, corynebacteria, a large number of anaerobes. In total, the microflora of the mouth has more than 200 species of microorganisms. On the surface of the mucosa, depending on the hygiene products used by the individual, about 10 3 -10 5 MK / mm2 are found. The colonization resistance of the mouth is carried out mainly by streptococci (S. salivarus, S. mitis, S. mutans, S. sangius, S. viridans), as well as representatives of the skin and intestinal biotopes. At the same time, S. salivarus, S. sangius, S. viridans adhere well to the mucous membrane and dental plaque. These alpha-hemolytic streptococci, which have a high degree of histadgesia, inhibit the colonization of the mouth by fungi of the genus Candida and staphylococci. The microflora transiently passing through the esophagus is unstable, does not show histadhesiveness to its walls and is characterized by an abundance of temporarily located species that enter from the oral cavity and pharynx. Relatively unfavorable conditions for bacteria are created in the stomach due to increased acidity, exposure to proteolytic enzymes, rapid motor-evacuation function of the stomach, and other factors that limit their growth and reproduction. Here, microorganisms are contained in an amount not exceeding 10 2 -10 4 per 1 ml of content.Eubiotics in the stomach master mainly the cavity biotope, the parietal microbiotope is less accessible to them. The main microorganisms active in the gastric environment are acid resistant representatives of the genus Lactobacillus with or without a histadhesive relationship to mucin, some types of soil bacteria and bifidobacteria. Lactobacilli, despite the short residence time in the stomach, are capable, in addition to their antibiotic action in the stomach cavity, to temporarily colonize the parietal microbiotope. As a result of the joint action of protective components, the bulk of microorganisms that have entered the stomach die. However, in case of malfunction of the mucous and immunobiological components, some bacteria find their biotope in the stomach. So, due to pathogenicity factors, the population of Helicobacter pylori is fixed in the gastric cavity. A little about the acidity of the stomach: The maximum theoretically possible acidity in the stomach is 0.86 pH. The minimum theoretically possible acidity in the stomach is 8.3 pH. Normal acidity in the lumen of the body of the stomach on an empty stomach is 1.5-2.0 pH. The acidity on the surface of the epithelial layer facing the lumen of the stomach is 1.5-2.0 pH. Acidity in the depth of the epithelial layer of the stomach is about 7.0 pH. MAIN FUNCTIONS OF THE SMALL INTESTINE Small intestine - This is a tube about 6m long. It occupies almost the entire lower part of the abdominal cavity and is the longest part of the digestive system, connecting the stomach to the large intestine. Most of the food is already digested in the small intestine with the help of special substances - enzymes (enzymes). To the main functions of the small intestine include cavity and parietal hydrolysis of food, absorption, secretion, as well as barrier-protective. In the latter, in addition to chemical, enzymatic and mechanical factors, the indigenous microflora of the small intestine plays a significant role. She takes an active part in the cavity and parietal hydrolysis, as well as in the absorption of nutrients. The small intestine is one of the most important links that ensure the long-term preservation of the eubiotic parietal microflora. There is a difference in the colonization of cavitary and parietal microbiotopes with eubiotic microflora, as well as in the colonization of tiers along the length of the intestine. The cavity microbiotope is subject to fluctuations in the composition and concentration of microbial populations; the wall microbiotope has a relatively stable homeostasis. In the thickness of the mucous overlays, populations with histadhesive properties to mucin are preserved. The proximal small intestine normally contains a relatively small amount of gram-positive flora, consisting mainly of lactobacilli, streptococci and fungi. The concentration of microorganisms is 10 2 -10 4 per 1 ml of intestinal contents. As we approach the distal parts of the small intestine, the total number of bacteria increases to 10 8 per 1 ml of content, at the same time additional species appear, including enterobacteria, bacteroids, bifidobacteria. MAIN FUNCTIONS OF THE LARGE INTESTINE The main functions of the large intestine are reservation and evacuation of chyme, residual digestion of food, excretion and absorption of water, absorption of some metabolites, residual nutrient substrate, electrolytes and gases, formation and detoxification of feces, regulation of their excretion, maintenance of barrier-protective mechanisms. All of these functions are performed with the participation of intestinal eubiotic microorganisms. The number of microorganisms in the colon is 10 10 -10 12 CFU per 1 ml of content. Bacteria account for up to 60% of stool. Throughout life, a healthy person is dominated by anaerobic species of bacteria (90-95% of the total composition): bifidobacteria, bacteroids, lactobacilli, fusobacteria, eubacteria, veillonella, peptostreptococci, clostridia. From 5 to 10% of the microflora of the colon are aerobic microorganisms: Escherichia, Enterococcus, Staphylococcus, various types of opportunistic enterobacteria (Proteus, Enterobacter, Citrobacter, Serrations, etc.), non-fermenting bacteria (pseudomonas, Acinetobacter), yeast-like fungi of the genus Candida and others Analyzing the species composition of the colon microbiota, it should be emphasized that, in addition to the indicated anaerobic and aerobic microorganisms, its composition includes representatives of nonpathogenic protozoan genera and about 10 intestinal viruses.Thus, in healthy individuals, there are about 500 species of various microorganisms in the intestines, most of which are representatives of the so-called obligate microflora - bifidobacteria, lactobacilli, non-pathogenic Escherichia coli, etc. 92-95% of the intestinal microflora consists of obligate anaerobes. 1. Predominant bacteria. Due to anaerobic conditions in a healthy person, anaerobic bacteria predominate (about 97%) in the composition of the normal microflora in the large intestine:bacteroids (especially Bacteroides fragilis), anaerobic lactic acid bacteria (eg Bifidumbacterium), clostridia (Clostridium perfringens), anaerobic streptococci, fusobacteria, eubacteria, veillonella. 2. Small part microflora make up aerobic andfacultative anaerobic microorganisms: gram-negative coliform bacteria (primarily Escherichia coli - E.Coli), enterococci. 3. In a very small amount: Staphylococci, Proteus, Pseudomonas, fungi of the genus Candida, certain types of spirochetes, mycobacteria, mycoplasmas, protozoa and viruses Qualitative and quantitative COMPOUND the basic microflora of the large intestine in healthy people (CFU/g faeces) varies depending on their age group. On the image features of the growth and enzymatic activity of bacteria in the proximal and distal parts of the large intestine are shown under various conditions of molarity, mM (molar concentration) of short-chain fatty acids (SCFA) and the pH value, pH (acidity) of the medium. « number of storeys resettlement bacteria» For a better understanding of the topic, we will give a brief definition.understanding the concepts of what aerobes and anaerobes are Anaerobes- organisms (including microorganisms) that receive energy in the absence of oxygen access by substrate phosphorylation, the end products of incomplete oxidation of the substrate can be oxidized with more energy in the form of ATP in the presence of the final proton acceptor by organisms that carry out oxidative phosphorylation. Facultative (conditional) anaerobes- organisms whose energy cycles follow the anaerobic path, but are able to exist even with the access of oxygen (that is, they grow both in anaerobic and aerobic conditions), in contrast to obligate anaerobes, for which oxygen is detrimental. Obligate (strict) anaerobes- organisms that live and grow only in the absence of molecular oxygen in the environment, it is detrimental to them. Normal human microflora is a set of many microbiocenoses characterized by certain relationships and habitats. In the human body, in accordance with the living conditions, biotopes with certain microbiocenoses are formed. Any microbiocenosis is a community of microorganisms that exists as a whole, connected by food chains and microecology. Types of normal microflora: 1) resident - permanent, characteristic of this species; 2) transient - temporarily trapped, uncharacteristic for a given biotope; She doesn't actively reproduce. Normal microflora is formed from birth. Its formation is influenced by the microflora of the mother and the nosocomial environment, the nature of feeding. Factors affecting the state of normal microflora. 1. Endogenous: 1) secretory function of the body; 2) hormonal background; 3) acid-base state. 2. Exogenous conditions of life (climatic, domestic, environmental). Microbial contamination is typical for all systems that have contact with the environment. In the human body, blood, cerebrospinal fluid, articular fluid, pleural fluid, lymph of the thoracic duct, internal organs: heart, brain, parenchyma of the liver, kidneys, spleen, uterus, bladder, lung alveoli are sterile. Normal microflora lines the mucous membranes in the form of a biofilm. This polysaccharide scaffold consists of microbial cell polysaccharides and mucin. It contains microcolonies of cells of normal microflora. The biofilm thickness is 0.1–0.5 mm. It contains from several hundred to several thousand microcolonies. The formation of a biofilm for bacteria creates additional protection. Inside the biofilm, bacteria are more resistant to chemical and physical factors. Stages of formation of normal microflora of the gastrointestinal tract (GIT): 1) accidental seeding of the mucosa. Lactobacilli, clostridia, bifidobacteria, micrococci, staphylococci, enterococci, Escherichia coli, etc. enter the gastrointestinal tract; 2) the formation of a network of tape bacteria on the surface of the villi. Mostly rod-shaped bacteria are fixed on it, the process of biofilm formation is constantly going on. Normal microflora is considered as an independent extracorporeal organ with a specific anatomical structure and functions. Functions of normal microflora: 1) participation in all types of exchange; 2) detoxification in relation to exo- and endoproducts, transformation and release of medicinal substances; 3) participation in the synthesis of vitamins (groups B, E, H, K); 4) protection: a) antagonistic (associated with the production of bacteriocins); b) colonization resistance of mucous membranes; 5) immunogenic function. The highest contamination is characterized by: 1) large intestine; 2) oral cavity; 3) urinary system; 4) upper respiratory tract; 2. Dysbacteriosis Dysbacteriosis (dysbiosis) is any quantitative or qualitative changes in the normal human microflora typical for a given biotope, resulting from the impact on a macro- or microorganism of various adverse factors. Microbiological indicators of dysbiosis are: 1) decrease in the number of one or more permanent species; 2) the loss of certain traits by bacteria or the acquisition of new ones; 3) increase in the number of transient species; 4) the emergence of new species unusual for this biotope; 5) weakening of the antagonistic activity of normal microflora. The reasons for the development of dysbacteriosis can be: 1) antibiotic and chemotherapy; 2) severe infections; 3) severe somatic diseases; 4) hormone therapy; 5) radiation exposure; 6) toxic factors; 7) deficiency of vitamins. Dysbacteriosis of different biotopes has different clinical manifestations. Intestinal dysbacteriosis can manifest itself in the form of diarrhea, nonspecific colitis, duodenitis, gastroenteritis, chronic constipation. Respiratory dysbacteriosis occurs in the form of bronchitis, bronchiolitis, chronic lung diseases. The main manifestations of oral dysbiosis are gingivitis, stomatitis, caries. Dysbacteriosis of the reproductive system in women proceeds as vaginosis. Depending on the severity of these manifestations, several phases of dysbacteriosis are distinguished: 1) compensated, when dysbacteriosis is not accompanied by any clinical manifestations; 2) subcompensated, when local inflammatory changes occur as a result of an imbalance in the normal microflora; 3) decompensated, in which the process is generalized with the appearance of metastatic inflammatory foci. Laboratory diagnosis of dysbacteriosis The main method is bacteriological examination. At the same time, quantitative indicators prevail in the evaluation of its results. Not specific identification is carried out, but only to the genus. An additional method is chromatography of the spectrum of fatty acids in the material under study. Each genus has its own spectrum of fatty acids. Correction of dysbacteriosis: 1) elimination of the cause that caused the imbalance of normal microflora; 2) the use of eubiotics and probiotics. Eubiotics are preparations containing live bactericinogenic strains of normal microflora (colibacterin, bifidumbacterin, bifikol, etc.). Probiotics are substances of non-microbial origin and foods containing additives that stimulate their own normal microflora. Stimulants - oligosaccharides, casein hydrolyzate, mucin, whey, lactoferrin, dietary fiber. Share on social networks: Audience 2 Audience 1 Preparations Audience 4 Folk remedies spbtr.ru - Diseases, endocrinologists. MRI Mass media registration certificate EL No. FS 77 - 57771 dated April 18, 2014. Copyright © 2006-2017. All materials are protected by copyright Mass media "BusinessGarant" is registered by the Federal Service for Supervision of Communications, Information Technologies and Mass Communications