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Microflora of the human body. Normal human microflora: meaning, types and functions

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 are formed in the human body in which a certain microbiocenosis settles. And any microbiocenosis is not just a certain amount 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 a given biotope, temporarily introduced (transient), it does not actively reproduce.

Normal human microflora is formed from the first moment a child is born. 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 hormonal background, acid-base state of blood, process of production and secretion by cells chemicals(so-called secretory function organism). By the age of three months, a microflora similar to the normal microflora of an adult is formed in the child’s body.

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

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

This film, no more than 0.5 mm thick, protects microorganisms from chemical and physical influence. But if the self-defense factors of microorganisms exceed the compensatory capabilities of the human body, then disturbances may occur, with the development pathological conditions And adverse consequences. These consequences include

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

The total number of microorganisms of the normal human flora reaches 10 14, which exceeds the number of cells of all tissues of an adult. The basis of 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 function).

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).
  • — Highlights antibacterial substances, suppressing the vital activity of pathogenic bacteria that have entered the body. The combination of mechanisms ensures the stability of normal microflora and prevents 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 with microorganisms

  • - leather;
  • - oral cavity, nose, pharynx;
  • - upper respiratory tract;
  • - large intestine;
  • - vagina.

Normally contain few microorganisms

How is normal intestinal microflora formed? First the mucous membrane gastrointestinal tract it is contaminated by lactobacilli, clostridia, bifidobacteria, micrococci, staphylococci, enterococci, E. coli and other microorganisms that accidentally entered it. Bacteria are fixed on the surface of the intestinal villi; in parallel, the process of biofilm formation occurs

All groups of microorganisms are identified as part of the normal human microflora: bacteria, fungi, protozoa and viruses. Microorganisms of normal human microflora are represented next births:

  • - oral cavity - Actinomyces (Actinomycetes), Arachnia (Arachnia), Bacteroides (Bacteroides), Bifidobacterium (Bifidobacteria), Candida (Candida), Centipeda (Centipeda), Eikenella (Eikenella), Eubacteriun (Eubacteria), Fusobacterium (Fusobacteria), Haemophilus (Haemophilus), Lactobacillus (Lactobacillus), Leptotrichia (Leptotrichia), Neisseria (Neisseria), Propionibacterium (Propionibacterium), Selenomonas (Selenomonas), Simonsiella (Simonsiella), Spirochaeia (Spirochea), Streptococcus (Streptococci), Veillonella (Veylonella), Wolinella (Wolinella), Rothia (Rotia);
  • - upper respiratory tract - Bacteroides, Branhamella, Corynebacterium, Neisseria, Streptococcus;
  • — small intestine- Bifidobacterium (Bifidobacteria), Clostridium (Clostridium), 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 (Coproco), ccus (Coprococci), Disulfomonas (Disulfomona), Escherichia (Escherichia), Eubacterium (Eubacteria), Fusobacterium (Fusobacteria), Gemmiger (Gemmiger), Lactobacillus (Lactobacillus), Peptococcus (Peptococcus), Peptostreptoccocus (Peptostreptococcus), Propionibacterium (Propionibacterium), Roseburia (Roseburia), Selenomonas (Selenomona), Spirochaeta (Spirochete), Succinomonas, Streptococcus (Streptococcus), Veillonella (Veylonella), Wolinella (Wolinella);
  • - skin - Acinetobacter, Brevibacterium, Corynebacterium, Micrococcus, Propiombacterium, Staphylococcus, Pityrosponim, Trichophyton;
  • - female genital organs - Bacteroides (Bacterioids), Clostridium (Clostridia), Corynebacterium (Corynebacterium), Eubacterium (Eubacteria), Fusobacterium (Fusobacteria), Lactobacillus (Lactobacilli), Mobiluncus (Mobiluncus), Peptostreptococcus (Peptostreptococcus), Streptococcus (Streptococcus), Spirochaeta (Spirochete), Veillonella (Veylonella).

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

The human body is populated (colonized) by more than 500 species of microorganisms,

components of the normal human microflora, in a state of equilibrium

(eubiosis) with each other and the human body. Microflora is a stable

community of microorganisms, i.e. microbiocenosis. It colonizes the surface of the body and

cavities communicating with the environment. Habitat of the community of microorganisms

called a biotope. Normally, microorganisms are absent from the lungs and uterus. Distinguish

normal microflora of the skin, mucous membranes of the mouth, upper respiratory tract,

digestive tract and genitourinary system. Among the normal microflora there are

resident and transient microflora. Resident (permanent) obligate microflora

represented by microorganisms that are constantly present in the body. Transitional

(fickle) microflora is not capable of long-term existence in the body.

The human body and its normal microflora constitute a single ecological system.

The formation of the microflora of newborns begins with the entry of microorganisms into

during the birth process on the skin and mucous membranes. Further formation of microflora

determined by the sanitary condition of the environment in which the birth took place, the type of feeding

etc. Normal microflora becomes stable by the end of the third month of life

similar to the microflora of an adult. Number of microorganisms in an adult

is about 1014 individuals, and obligate species predominate to a large extent

anaerobes.

Representatives of normal microflora are enclosed in an exo-polysaccharide-mucin matrix,

forming a biological film on the mucous membranes and skin that is resistant to various

influences.

The microflora of the skin has great value in the spread of microorganisms in the air. IN

as a result of desquamation (peeling) several million scales, each carrying

several microorganisms pollute the environment. On the skin and in its deeper

layers (hair follicles, sebaceous and sweat glands) there are 3.10 times more anaerobes,

than aerobes. The skin is colonized by propionibacteria, coryneform bacteria, staphylococci,

streptococci, yeast Pityrosporum, yeast-like fungi Candida, rarely micrococci, Mus.

fortuitum. There are less than 80,000 microorganisms per 1 cm2 of skin. Normally this amount

does not increase as a result of the action of bactericidal sterilizing factors of the skin, in

in particular, a-globulin, immunoglobulins A, G, transferrin, lysozyme were found in skin sweat

and other antimicrobial substances. The process of skin self-cleansing is enhanced by pure

washed skin. Increased growth of microorganisms occurs on dirty skin; when weakening

In the body, multiplying microorganisms determine body odor. Through dirty hands

Contamination (contamination) of medicines with skin microorganisms occurs, which

leads to subsequent spoilage of drugs.

Dust particles loaded with microorganisms enter the upper respiratory tract,

most of which are retained in the nasopharynx and oropharynx. Bacteroides grow here,

coryneform bacteria, Haemophilus influenzae, peptococci, lactobacteria, staphylococci,

streptococci, non-pathogenic Neisses series, etc. The trachea and bronchi are usually sterile.

The microflora of the digestive tract is the most representative in its

qualitative and quantitative composition. At the same time, microorganisms live freely in

cavities of the digestive tract, and also colonize the mucous membranes.

The oral cavity is inhabited by actinomycetes, bacteroides, bifidobacteria, eubacteria,

fusobacteria, lactobacilli, hemophilus influenzae, leptotrichia, neisseria, spirochetes,

streptococcus

ki, staphylococci, veillonella, etc. Fungi of the genus Candida and protozoa are also found.

Associates of normal microflora and their metabolic products form dental plaque.

The microflora of the stomach is represented by lactobacilli and yeast, a few gram-negative

bacteria. It is somewhat poorer than, for example, the intestines, since gastric juice has

low pH value, unfavorable for the life of many microorganisms. For gastritis,

stomach ulcers reveal curved shapes of bacteria. Helicobacter pylori,

which are etiological factors pathological process.

IN small intestine there are more microorganisms than in the stomach; found here

bifidobacteria, clostridia, eubacteria, lactobacilli, anaerobic cocci. Greatest

the number of microorganisms accumulates in the colon. 1 g of feces contains up to

250 billion microbial cells. About 95% of all types of microorganisms are anaerobes.

The main representatives of the colon microflora are: gram-positive

anaerobic bacilli (bifidobacteria, lactobacilli, eubacteria); gram-positive

spore-forming anaerobic bacilli (clostridia, perfringens, etc.); enterococci; gram-

negative anaerobic rods (bacteroides); gram-negative optional

anaerobic bacilli (Escherichia coli and similar bacteria of the family Enterobacteriaceae.

Citrobacter, Enterobacter, Klebsiella, Proteus, etc.). In smaller quantities

Fusobacteria, propionibacteria, veillonella, peptococci, staphylococci are found,

Pseudomonas aeruginosa, yeast-like fungi, as well as protozoa, viruses, including phages. On

epithelia successfully grow spirochetes and filamentous bacteria. Bifidobacteria and bacteroides

make up 80.90% of total number intestinal microflora.

The microflora of the colon plays an important role in human life. peculiar

extracorporeal organ. It is an antagonist of putrefactive microflora, since

produces lactic, acetic acids, antibiotics, etc. Its role in water-

salt metabolism, regulation of intestinal gas composition, metabolism of proteins, carbohydrates, fatty

acids, cholesterol and nucleic acids, as well as products of biologically active

connections. antibiotics, vitamins, toxins, etc. Morphokinetic role of microflora

lies in its participation in the development of organs and systems of the body; she takes part

also in physiological inflammation of the mucous membrane and change of epithelium, digestion and

detoxification of exogenous substrates and metabolites, which is comparable to liver function.

Normal microflora also plays an antimutagenic role, destroying carcinogenic

substances

in the intestines. At the same time, some bacteria can produce strong mutagens.

The intestinal parietal microflora colonizes the mucous membrane in the form of microcolonies,

forming a kind of biological film consisting of microbial bodies and exopoli-

saccharide matrix. Exopolysaccharides of microorganisms, called glycocalyx,

protect microbial cells from a variety of physicochemical and biological

influences. The intestinal mucosa is also protected by biological

The intestinal microflora has a significant influence on the formation and maintenance

immunity. The intestines contain about 1.5 kg of microorganisms, the antigens of which

stimulate the immune system. Natural nonspecific stimulator of immunogenesis

is a muramyl dipeptide formed from microflora under the influence of lysozyme and other lithium-

ical enzymes found in the intestines.

The most important function of normal intestinal microflora is its participation in colonization

resistance, which is understood as a combination of the body’s protective factors and

competitive, antagonistic and other features of intestinal anaerobes, giving

stability of microflora and preventing colonization of mucous membranes by foreigners

microorganisms. In order to prevent infectious complications, at reduced

body resistance and increased risk of autoinfection, in cases of extensive injuries,

burns, immunosuppressive therapy, organ and tissue transplantation are carried out

activities aimed at preserving and restoring colonization resistance

Tension. Based on this, selective decontamination is carried out. selective

removal of aerobic bacteria and fungi from the digestive tract to increase

the body's resistance to infectious agents. Selective decontamination is carried out

by prescribing for oral administration low-absorbable chemotherapy drugs that suppress

aerobic part and not affecting anaerobes, for example, complex administration of vancomycin,

gentamicin and nystatin.

Normal vaginal microflora includes bacteroides, lactobacilli, peptostreptococci and

clostridia.

Representatives of normal microflora, when the body’s resistance decreases, can

cause purulent-inflammatory processes, i.e. normal microflora can become

source of autoinfection or endogenous infection. It is also the source of genes

for example genes drug resistance to antibiotics. Moreover, as has already happened

As stated above, intestinal microflora, entering the environment, can

pollute soil, water, air, food, etc. Therefore its discovery

indicates contamination of the object under study with human secretions.

State of eubiosis. dynamic balance of microflora and the human body. Maybe

be disrupted under the influence of environmental factors, stress, broad and

uncontrolled use of antimicrobial drugs, radiation and chemotherapy. IN

As a result, colonization resistance is impaired. Abnormally multiplied

microorganisms produce toxic metabolic products. indole, skatole, ammonia,

hydrogen sulfide. A condition that develops as a result of loss of normal functions

microflora is called dysbacteriosis or dysbiosis. When dysbacteriosis occurs

quantitative and qualitative changes bacteria that are part of the microflora. At

In dysbiosis, changes also occur among other groups of microorganisms. viruses, fungi and

Dysbiosis and dysbacteriosis are considered an endogenous infection that occurs most often in

as a result of violation antimicrobials normal microflora.

To restore normal microflora, probiotics (eubiotics, see below) are prescribed.

Chapter 9), obtained from freeze-dried living bacteria, representatives of normal

intestinal microflora. bifidobacteria, Escherichia coli, lactobacilli, etc.

14. Normal human microflora

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

Types of normal microflora:

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

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

Factors influencing the state of normal microflora.

1. Endogenous:

1) secretory function of the body;

2) hormonal levels;

3) acid-base state.

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

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

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

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

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

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

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

Functions of normal microflora:

1) participation in all types of exchange;

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

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

4) protection:

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

b) colonization resistance of mucous membranes;

5) immunogenic function.

The highest contamination rates are characterized by:

1) large intestine;

2) oral cavity;

3) urinary system;

4) upper respiratory tract;

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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 with bacteria. Moreover, the number of bacteria inhabiting the integumentary tissues (skin, mucous membranes) is many times greater than the number of the host’s own cells. Quantitative fluctuations of bacteria in a biocenosis can reach several orders of magnitude for some bacteria and, nevertheless, fit into accepted standards.

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

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

Types of normal microflora:

1) resident– constant, characteristic of this species. Quantity characteristic species relatively small and relatively stable, although numerically they are always represented most abundantly. Resident microflora is found in certain places of the human body, and an important factor is his age;

2) transient– temporarily introduced, not typical for a given biotope; it does not actively reproduce, therefore, although the species composition of transient microorganisms is diverse, they are not numerous. Characteristic feature This type of microflora is that, as a rule, when it gets on the skin or mucous membranes from the environment, it does not cause diseases and does not permanently live 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 supply of microorganisms from the environment, but also by the state of the host’s immune system and the composition of the permanent normal microflora. The composition of transient microflora is not constant and depends on age, external environment, working conditions, diet, past 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 hospital environment, and the nature of feeding. The colonization of the body by bacteria 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 within biocenoses. Microbial contamination is typical for all systems that have contact with the environment. However, normally many tissues and organs of a healthy person are sterile, in particular blood, cerebrospinal fluid, joint fluid, pleural fluid, thoracic duct lymph, internal organs: heart, brain, liver parenchyma, kidneys, spleen, uterus, bladder, lung alveoli . Sterility in in this case is provided by nonspecific 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 of this body, biotype or section thereof.

The highest contamination rates are characterized by:

1) large intestine. The normal microflora is dominated by anaerobic bacteria (96–99%) (bacteroides, 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. Normal microflora of different departments oral cavity varies and is determined by the biological characteristics of the species living here. Representatives of the oral microflora 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 external 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, bacteroides). Mycobacteria smegma, staphylococci, mycoplasmas and saprophytic treponemas are localized on the external genitalia of men and women;

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, and 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 airways and consists of: neisseria, diphtheroids, α- and β-hemolytic streptococci, enterococci, mycoplasmas, coagulase-negative staphylococci, moraxella, bacteroides, borrelia, treponemes and actinomycetes. In the upper respiratory tract Streptococci and Neisseria predominate, staphylococci, diphtheroids, Haemophilus influenzae bacteria, pneumococci, mycoplasmas, bacteroides are found;

5) leather, especially her hairy part. Due to constant contact with the external environment, the skin is a habitat for transient microorganisms, while having permanent microflora, the composition of which varies 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 characteristics and other 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. The 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 represent 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 normal microflora cells. 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.

The formation of a biofilm provides additional protection for bacteria. Inside a biofilm, bacteria are more resistant to chemical and physical factors.

Factors influencing the state of normal microflora:

1) endogenous:

a) secretory function of the body;

b) hormonal levels;

c) acid-base state;

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

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

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

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

2. Basic functions of normal microflora

Normal microflora is considered as an independent extracorporeal organ with a certain 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 normal microflora, constantly maintain the immune system in proper condition with their antigens.

3. Digestive function . Normal microflora takes part in cavity 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 is known, in the process of metabolism, individual representatives of normal microflora form vitamins. Thus, bacteria of the large intestine synthesize biotin, riboflavin, pantothenic acid, vitamins K, E, B2, folic acid, are not absorbed in the large intestine, so you should count only on those that are small quantity are formed in the ileum.

6. Detoxification function. Normal microflora is capable of neutralizing toxic metabolic products formed in the body or organisms from the external environment through 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. Normal microflora in this case is an unlimited bank of genetic material, since the exchange of genetic material constantly occurs both between 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 important role in the conversion of bile pigments and bile acids, absorption 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 of various unfavorable factors on a macro- or microorganism.

Microbiological indicators of dysbiosis are:

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

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

3) increase in the number of transient species;

4) the emergence of new species not typical for a given biotope;

5) weakening of the antagonistic activity of normal microflora.

The causes of dysbacteriosis may be:

1) antibiotic and chemotherapy;

2) severe infections;

3) heavy somatic diseases;

4) hormone therapy;

5) radiation exposure;

6) toxic factors;

7) vitamin deficiency.

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

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

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

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

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

Laboratory diagnostics dysbacteriosis

Basic method – bacteriological examination. At the same time, quantitative indicators prevail in assessing its results. Species identification is not 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 dysbiosis:

1) eliminating 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, bificol, etc.).

Probiotics– these are substances of non-microbial origin and food products containing additives that stimulate their own normal microflora. Stimulating substances – oligosaccharides, casein hydrolysate, mucin, whey, lactoferin, dietary fiber.

The concept of microbiocenosis

Normal microflora accompanies its owner throughout his life. Its significant importance in maintaining the vital functions of the body is evidenced by observations of gnotobiont animals (devoid of their own microflora), whose life differs significantly from that of normal individuals, and sometimes is simply impossible. In this regard the doctrine of normal human microflora and its disorders represents a very significant branch of medical microbiology.

Currently, it is firmly established that the human body and the microorganisms inhabiting it are a single ecosystem.

From a modern perspective, normal microflora should be considered as a collection of many microbiocenoses, characterized by a certain species composition and occupying one or another biotype in the body. In any microbiocenosis should be distinguished:

  • indigenous, autochthonous flora - characteristic, constantly occurring types of microorganisms. Their number is relatively small, but numerically they are always represented most abundantly;
  • allochthonous flora - transient, additional and random. The species composition of such microorganisms is diverse, but they are few in number.

The surfaces of the skin and mucous membranes of the human body are abundantly populated with bacteria. Moreover, the number of bacteria inhabiting the integumentary tissues (skin, mucous membranes) is many times greater than the number of the host’s own cells. Quantitative fluctuations of bacteria in a biocenosis can reach several orders of magnitude for some bacteria and nevertheless fall within the accepted standards. Formed microbiocenosis exists as a single whole. as a community of species united by food chains and related by microecology.

The totality of microbial biocenoses found in the body of healthy people is normal human microflora.

Currently, normal microflora is considered as an independent extracorporeal organ. It has a characteristic anatomical structure- biofilm, and it has certain functions.

It has been established that normal microflora has a fairly high species and individual specificity and stability.

Features of normal microflora

Normal microflora of individual biotopes different, but subject to a number of basic laws:

  • it is quite stable;
  • forms a biofilm;
  • represented by several species, among which dominant species and filler species are distinguished;
  • Anaerobic bacteria are predominant.

Normal microflora is characterized anatomical features- each ecological niche has its own species composition.

Some biotopes are stable in composition, while others (transient microflora) are constantly changing depending on external factors.

Microorganisms that make up the normal microflora form a clear morphological structure - a biofilm, the thickness of which ranges from 0.1 to 0.5 mm.

Biofilm is a polysaccharide framework consisting of microbial polysaccharides and mucin, which is produced by the cells of the macroorganism. In this framework, microcolonies of bacteria are immobilized - representatives of normal microflora, which can be located in several layers.

The normal microflora includes both anaerobic and aerobic bacteria, the ratio of which in most biocenoses is 10: 1-100: 1.

Colonization by bacteria various areas the body begins at the moment of birth of a person and continues throughout his life.

The formation of the qualitative and quantitative composition of normal microflora is regulated by complex antagonistic and synergistic relationships between its individual representatives within biocenoses.

Composition of transient microflora may vary depending on:

  • from age;
  • environmental conditions;
  • working conditions, diet;
  • past diseases;
  • injuries and stressful situations.

As part of normal microflora distinguish:

  • permanent, or resident microflora - is represented by a relatively stable composition of microorganisms, usually found in certain places of the human body in people of a certain age;
  • transient, or temporary microflora - enters the skin or mucous membranes from the environment, without causing diseases and not permanently living on the surfaces of the human body. It is represented by saprophytic opportunistic pathogens

‘ 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 supply of microorganisms from the environment, but also by the state of the host’s immune system and the composition of the permanent normal microflora.

Normally, many tissues and organs of a healthy person are free of microorganisms, i.e., sterile. These include:

  • internal organs;
  • brain and spinal cord;
  • alveoli of the lungs;
  • inner and middle ear;
  • blood, lymph, cerebrospinal fluid;
  • uterus, kidneys, ureters and urine in the bladder.

This is ensured by the presence of nonspecific cellular and humoral factors immunity, preventing the penetration of microbes into these tissues and organs.

On all open surfaces and in all open cavities, a fairly stable microflora is formed, specific to a given organ, biotope or its area - epitope. The richest in microorganisms:

  • oral cavity;
  • large intestine;
  • upper respiratory system;
  • external parts of the genitourinary system;
  • skin, especially the scalp.