The Influence Of Microflora On Human Health: Causes And Signs Of Disorders

Microbiota as a separate organ in the human body

The microbiota is, to some extent, a new organ of the human body. To begin with, we will deal with the origin of this organ and the history of its study. The intestine is the first organ associated with the emergence of our multicellular ancestors. It looked like a tube: an entrance, an exit, muscles, and in the middle of the tube an intestine in which bacteria lived. The gut is the perfect environment for bacteria because it's dark, warm, and there's food.

It has undergone many changes throughout its evolution. At some point, an immune system appeared that helped maintain a balance inside the intestines, sorting out good and bad bacteria. Then, for this organism, organs of movement and organs of perception of the world appeared, which reacted to light.

Over time, the brain and circulatory system developed, carrying nutrients from the intestines throughout the body. The brain has developed, and we began to perceive the world and decided that the brain is the main thing, but we forgot about the intestines. This evolutionary process has been going on for millions of years, but at the same time, the last 100-120 years have seen the evolution of technology.

Thanks to these technologies and the study of the human genome, we have been reminded of the importance of the gut. In 2012, scientists published the Human Microbiome Project, which revealed that over 10,000 different types of microorganisms live in the human body.

The gut microbiota in the gastrointestinal tract is the largest in the body. It has one hundred billion microorganisms, which exceeds the number of cells in the human body by 5-10 times. It is extremely important for the normal functioning of the intestinal immune system. She receives resources for her own metabolism from our food (in particular, from dietary fiber).

At the same time, the intestinal microbiota is directly involved in the process of food digestion (in fermentation, nutrient absorption, vitamin synthesis, etc.). It is interesting that the colonization by microorganisms occurs even during fetal development, is transmitted from mother to baby, which is why proper and nutritious nutrition during pregnancy is extremely important.

Functions of normal microflora:

• creation of colonization resistance;

• regulation of the gas composition and other cavities of the host organism;

• production of enzymes involved in the metabolism of proteins, carbohydrates, lipids, as well as improved digestion and increased intestinal motility;

• participation in water-salt metabolism;

• participation in providing eukaryotic cells with energy;

• detoxification of exogenous and endogenous substrates and metabolites mainly due to hydrolytic and reducing reactions;

• production of biologically active compounds (amino acids, peptides, hormones, fatty acids, vitamins);

• immunogenic function.

The most important function of normal microflora is its participation in the creation of colonization resistance (resistance, resistance to colonization by foreign microflora). The mechanism of creating colonization resistance is complex. Colonization resistance is ensured by the ability of some representatives of the normal microflora to adhere to the epithelium of the intestinal mucosa, forming a parietal layer on it and thereby preventing the attachment of pathogenic and opportunistic pathogens of infectious diseases.

Signs and causes of microbiota disturbance

Back in 1681, A. Leeuwenhoek identified microorganisms in human feces and put forward a hypothesis about the coexistence of various types of bacteria in the gastrointestinal tract (GIT). In 1888 I.I. Mechnikov suggested that the cause of many diseases is the cumulative effect on the cells and tissues of the macroorganism of various toxins and other metabolites produced by bacteria that live in the gastrointestinal tract in many. In his work “Etudes of Optimism”, he wrote that the numerous associations of microbes that inhabit the human intestines largely determine his spiritual and physical health.

The term "dysbacteriosis" was first introduced by the German physician Alfred Nissle in 1916 and meant disorders of the intestinal microflora associated with a change in the amount of Escherichia coli. However, the term dysbacteriosis can be applied not only to the intestines.

Each person's microflora is individual and stable for a long time. But a number of factors can change the balance, and this leads to disruption of not only the gastrointestinal tract (GIT), but the whole organism. Among these factors:

• harmful effects of the environment;

• viruses and bacteria;

• stress;

• taking antibiotics;

• inadequate and unbalanced nutrition;

• diseases of other organs and systems.

As a result of a violation of the composition of the microflora, symptoms such as bloating, rumbling in the abdomen, belching, heartburn may appear, intestinal function may be disturbed (constipation, diarrhea or unstable stools). In addition, due to changes in the absorption and synthesis of vitamins and trace elements, other organs may suffer.

This is reflected in the condition of the skin, nails and hair, general well-being suffers, weakness, fatigue appear, efficiency and, importantly, mood decrease. Violation of the composition of the microflora can lead to a change in eating behavior: you want more sweet, fatty, fast food. All this ultimately has a bad effect on the state of the gastrointestinal tract and the whole organism.

The biological balance between man and microflora, which has developed as a result of evolution, is a kind of indicator of the state of the macroorganism. The composition of the microflora is a sensitive indicator of the state of microbial ecosystems and the host-microflora ecosystem as a whole. Changes in the composition of the human microbiota under adverse conditions of the existence of the host (starvation, stressful situations, physical overload in certain professional groups - divers, swimmers, sailors), with various somatic diseases, as well as with radiation therapy, the use of immunosuppressants, etc. are shown. there is a decrease in the level of indicators of nonspecific resistance of the organism - complement, lysozyme, bactericidal activity of sera, etc.

However, insufficiently controlled use of antibiotics, especially with a wide spectrum of action, is of the greatest importance in disrupting the evolutionarily established microbial ecosystems and the host ecosystem as a whole - the microflora.

In this regard, the following serious problems for medicine have arisen:

1. Changes in etiol, the structure of infectious morbidity - the growth of infections caused by representatives of normal microflora, not only its optional part, the position of which in the normal microbial cenosis has not yet been finally determined (pseudomonas, proteus, fungi, etc.), but also obligate (bacteroids, lactobacterin, enterococci).

2. An increase in the number of "mixed" infections caused by the combined action of a number of opportunistic microorganisms.

3. The emergence of the problem of nosocomial (nosocomial) infections.

4. Decrease in the therapeutic effect of antibiotics due to the wide spread of forms of microorganisms resistant to them (especially carriers of multidrug resistance factors).

Intestinal microflora

The total amount and composition of the bacterial microflora differ significantly in individual parts of the gastrointestinal tract and depend on the pH value and oxygen concentration. The smallest number of bacteria is present in the stomach, in the lumen of which the low pH value serves as the main growth-limiting factor. So, in the stomach, mainly representatives of Lactobacillus spp., Streptococcus spp., Stomatococcus, etc. are detected.

The bulk of the bacteria lives in the pyloric part of the stomach; often they are firmly connected with its mucous membrane. In the duodenum of a healthy person, the number of microorganisms does not exceed 104-105 CFU / ml, and the species composition is represented by lactobacilli, bifidobacteria, bacteroids, enterococci, and yeast-like fungi. The overgrowth of bacteria in the small intestine is prevented by:

• secretion of hydrochloric acid in the stomach, preventing the multiplication of microbes in the upper gastrointestinal tract;

• ileocecal valve, which prevents the flow of contents from the large intestine into the small intestine;

• high propulsive motility of the small intestine, excluding stagnation of intestinal contents.

In the proximal parts of the small intestine, aerobic bacteria predominate: enterobacteria, streptococci, staphylococci, peptostreptococci. In the distal sections, the species composition is much wider - enterobacteria and anaerobic bacteria (bacteroids, bifidobacteria, lactobacilli, E. coli, eubacteria, etc.).

The obligate (main) microflora of the large intestine is represented by anaerobic bacteria (bifidobacteria, lactobacilli, bacteroids, non-pathogenic strains of clostridia, etc.), which make up 90–98% of the total number of microorganisms. The obligate microflora is directly involved in many vital processes of the macroorganism within the gastrointestinal tract itself, and also has numerous and varied systemic regulatory functions.

The accompanying (facultative) microflora (5–10%) consists of aerobic and conditionally anaerobic bacteria (E. coli, streptococci, enterococci). Transient (residual) microflora (0.01-0.5%) are staphylococci, clostridia, Proteus, fungi of the genus Candida. Representatives of the microbiota in the large intestine are unevenly distributed. Bifidobacteria colonize predominantly the caecum, ascending and descending colon; coli and streptococci - all sections of the large intestine, lactobacilli - all its sections, with the exception of the rectum; conditionally pathogenic strains (Klebsiella spp., Enterobacterspp., Hafnia, Serratia, Proteus, Morganella, Providencia, Citrobacter, etc.) - descending colon and sigmoid colon.

The gut microbiota has enormous metabolic potential and is able to carry out many biochemical processes, contributing to human physiology.

The microbiota can be divided into parietal and luminal. Lumen is located in the lumen of the gastrointestinal tract, does not interact with the mucosa. It feeds on insoluble dietary fiber, to which it attaches, digests them, and delivers micro- and macronutrients to the parietal microbiota. The parietal microbiota lives permanently in the parietal mucus of the gastrointestinal tract. The substrate for its vital activity is soluble dietary fiber. This is the type of microbiota that is inherited, it cannot be influenced in any way.

1. Protective - one of the most important functions of the intestinal microflora - ensuring colonization resistance, which is a set of mechanisms that determine the stable composition of the microflora and prevent the colonization of the host organism by opportunistic and pathogenic microorganisms.

2. The digestive function is realized both through the regulation of intestinal functions and through the direct utilization of nutrient substrates. The obligate microflora of the large intestine normally ensures the final hydrolysis of proteins, saponification of fats, fermentation of high-molecular carbohydrates that are not absorbed in the small intestine. Some dietary substances can only be metabolized by intestinal microflora. So, the saccharolytic microflora breaks down cellulose and hemicellulose to short-chain fatty acids.

3. Detoxifying, anti-carcinogenic - normal microflora is able to neutralize many toxic substrates and metabolites (nitrates, xenobiotics, histamine, mutagenic steroids), protecting enterocytes and distant organs from the effects of damaging factors and carcinogens. It has been proven that Bifidobacterium longum and Lactobacillus acidophilus in the intestinal lumen reduce lipid peroxidation by 28–48%.

1. The synthetic function lies in the fact that the normal microflora provides the synthesis of many macro- and micronutrients: vitamins B, C, K, folic and nicotinic acids. Only E. coli synthesizes 9 vitamins. The synthesis of hormones and biologically active substances underlies the regulatory action of microflora on the functions of internal organs and the central nervous system.

2. Immunogenic - the intestinal mucosa has its own lymphoid tissue, which is one of the significant components of the immune system of the macroorganism. About 80% of immunocompetent cells are localized in the intestinal mucosa. 25% of the intestinal mucosa consists of immunologically active tissue. Thus, the intestine can be considered as the largest "immune organ" of a person. The microflora is involved in the formation of both local and systemic immunity.

3. Regulation of the exchange of cholesterol, oxalates - bifidobacteria and lactobacilli reduce the absorption of cholesterol, converting it into insoluble coprostanol. Some lactobacilli under anaerobic conditions are involved in the metabolism of oxalates and lead to a decrease in the excretion of oxalates in the urine.

Severe microbiota disorders with an increase in the number of antibiotic-resistant pathogenic microorganisms occur with prolonged and uncontrolled use of broad-spectrum antibiotics. In addition, the use of narcotic and local anesthetic substances, laxatives, expectorants, psychotropic and many other drugs can lead to dysbiotic disorders.

Endogenous factors include acute and chronic diseases of the gastrointestinal tract, immunodeficiency states of various origins, severe chronic infections, metabolic disorders, surgical interventions, age (infant, senile).

Currently, the term “dysbiosis” and not “dysbacteriosis” is considered the most correct, since the composition of microorganisms that colonize the large intestine includes not only bacteria, but also yeast-like fungi, as well as several types of enteroviruses (rotaviruses, astroviruses, etc.). Dysbiosis implies quantitative and qualitative changes in the microecology of the large intestine with the development of metabolic, trophic, immunological and other disorders.

It is important to remember that disorders of the intestinal microbiota are always secondary and are not an independent diagnosis. Dysbiosis is not a disease, but a clinical and laboratory syndrome that develops as a result of changes in the environment and diet, gastrointestinal diseases, the use of drugs, etc.

Skin microflora

The microbiome, or microflora of the skin, is a collection of microorganisms that live on its surface, not only coexisting, but also interacting with the cells of the epidermis. The laws and principles of this "cooperation" are regulated by evolution. And if earlier experts associated skin health with its almost sterile purity, today they have come to understand that a rich microbiome, on the contrary, protects us from many problems. A diverse ecosystem is considered more resilient.

Various microorganisms on the skin are classified, depending on their effect on humans:

• Commensals are "friendly" microbes that usually do not cause any side effects.

• Symbionts are microbes that are beneficial to the host.

• Pathogens are disease-causing microbes.

Most microorganisms on the skin are commensals. They can prevent colonization by pathogens. To do this, commensals use the food sources that harmful microbes need to survive and produce toxic substances that prevent pathogens from sticking to skin cells.

Microbes can cause various infectious and non-infectious diseases of the epidermis, dermis, subcutaneous tissue and hair follicles. These can be completely harmless infections, and potentially life-threatening.

The pathogenicity of the infection is increased by the following factors:

• Violation of the skin barrier - for example, due to dermatitis or as a result of the use of a medical instrument.

• The use of immunosuppressants.

• Oncological diseases.

• AIDS virus.

• Very young or, conversely, advanced age.

• genetic reasons.

Microorganisms that are constantly present in a certain part of the human body are called resident microbiota. It is found in the upper layers of the epidermis, in and around hair follicles.

Resident microbiota include:

• Staphylococcus.

• Micrococcus.

• Corynebacteria.

• Brevitbacteria.

• Dermabacter.

• Malassezia.

The skin, like the intestines, is home to more than a trillion microorganisms. They all serve a purpose and are important for balance. And when it is violated, it inevitably leads to problems.

These hordes of bacteria, viruses and fungi are the invisible warriors that stand guard over the health of the skin.

Why the skin needs a microbiome:

• It protects the epidermis from temperature extremes, dust, ultraviolet and electromagnetic radiation.

• Accelerates wound healing.

• Participates in skin regeneration processes.

• Regulates its water and acid balance.

The skin performs the function of not only a physical barrier, but also an immunological one. Its cells clearly distinguish between commensals and pathogens, despite the constant exposure to a colossal number of microorganisms.

The immune response of the skin can be out of balance in some dermatological diseases, such as atopic dermatitis and psoriasis.

The skin is constantly exposed to environmental agents - from harsh detergents to certain drugs and cosmetics. All this can disrupt the normal microbial composition of the skin. And dysbiosis in the “bacteria-host” system, in turn, can lead to diseases.

Factors that disrupt the skin microbiome:

• Abuse of antibacterial agents, including topical antibiotics. They can be used strictly according to the doctor's prescription.

• Sun exposure without sunscreen.

• An excess of simple carbohydrates in the diet - pathogenic microbes "adore" sweets.

• Constant stress and anxiety.

• Neglect of skin care rules (cleansing, protection from wind and frost).

To restore the skin microbiome, it is not enough just to use external agents. This is a whole strategy, but, fortunately, its rules are available to many.

How to restore the microbiome of the skin of the face:

• Lead a healthy lifestyle that includes a balanced diet and sufficient physical activity.

• Carefully care for your skin, choosing products suitable for your type.

• Use cosmetics with pre- and probiotics in the composition.

• Avoid antibacterial soaps by choosing organic ones.

• Set up sleep patterns. “Correct” circadian rhythms are of great importance for our health, including for the skin microbiome.

In addition, there is evidence of a benefit to the skin microflora of soil organisms (SBOs). They are natural strains of probiotics in the skin and in the gut. Therefore, some experts recommend that city dwellers spend time outdoors or engage in gardening to maintain skin health.

Microflora of the vagina

The anatomical and functional well-being of the female reproductive system is ensured by a multi-stage system that protects the genitals from infections. The closed genital slit and the intact hairline of the pubic and perineal area, as well as the aggressive pH level of the vagina (4.0–4.5), which limits the growth of microorganisms that are unable to exist and multiply in an acidic environment, mechanically prevent the entry of unwanted microorganisms into the vagina.

The role of the barrier is also performed by the cervix, provided that it is anatomically intact, which creates the preconditions for a high concentration of local immunity factors in the cervical mucus. In addition, nature provides for monthly rejection of the functional layer of the endometrium in the absence of pregnancy.

In a healthy vaginal ecosystem, there are several interdependent and interdependent defense mechanisms against various infections: vaginal epithelium, vaginal microflora (peroxide-producing lactobacilli), humoral and cellular immunity. Thus, a necessary condition for the creation and maintenance of a physiological state is a mature epithelium, which plays an important role in the colonization of the vagina by lactobacilli and the maintenance of their vital activity. Estrogens induce the accumulation of glycogen in the vaginal epithelium, which is a metabolic substrate for lactobacilli, and also stimulate the formation of receptors for lactobacilli on epithelial cells.

In turn, lactobacilli break down glycogen to form lactic acid, which provides an acidic environment in the vagina (pH 4.0–4.5), and hydrogen peroxide, which act as natural antiseptics. The acidic environment in the vagina, favorable for acid-resistant microorganisms, creates a natural filter, as a result of which most pathogens and opportunistic microbes die. In addition, lactobacilli actively compete with other microorganisms for the possibility of adhesion to the cells of the vaginal epithelium, thereby stimulating the immune system of the macroorganism.

It must be understood that the vaginal microbiome is not only unstable, but also a heterogeneous environment. While some of the microbial communities that make up it change rapidly, others are characterized by relative constancy. The formation of the vaginal microbiota in girls begins from the moment of birth. On the eve of childbirth, with a normal pregnancy, the level of estrogen in a woman's body reaches a peak. This stimulates the accumulation of glycogen in the cells of the vaginal epithelium, increasing the number of colonies of lactobacilli, and ensures the maximum contamination of the newborn with the necessary microflora.

If, immediately after birth, an acidic environment is created in the girl's vagina (pH 4.4–4.6), then by the end of the first month of life, the vaginal epithelium becomes thin, the glycogen content decreases, and the pH rises to 7.0. That is why it is so necessary that from an early age the girl strictly observes the rules of personal hygiene.

During puberty, physiological hormonal changes entail changes in the structure and function of the vaginal epithelium. Against the background of an increase in estrogen saturation, the level of lactobacilli increases, the vaginal environment becomes acidic. In healthy women of reproductive age, the composition of the microflora varies depending on the phase of the cycle. The main protective mechanism also depends on the phase of the cycle: before ovulation, the aggressive pH of the environment plays a leading role, and after ovulation, cervical mucus plays a leading role.

Although dynamic changes in the vaginal microbiome are quite natural, normally they should not have a drastic effect on the vital activity of lactobacilli. Achieving this task is complicated by the fact that lactobacilli are quite vulnerable compared to opportunistic and pathogenic microorganisms.

Thus, a healthy vaginal ecosystem is characterized by intact epithelium, the presence of a sufficient amount of lactobacilli microflora and an adequate state of local immunity. Violations of the state of the vaginal microbiome are associated with the development of one of 4 types of infections: bacterial vaginosis (anaerobic microflora predominates), aerobic/nonspecific vaginitis (aerobic microflora predominates), vulvovaginal candidiasis, trichomoniasis. Which disease will develop depends largely on the virulence of the pathogen or their association, the characteristics of the vaginal microbiome, and the intensity of the immune response.

Thus, aerobic vaginitis is characterized by a strong immune response, severe inflammation, high levels of interleukins 1, 6, 8, etc. Bacterial vaginosis is characterized by a lack of inflammation and a reduced immune response.

The microflora of the oral cavity

The mucous membrane of the upper respiratory tract represents the body's first line of defense against a variety of environmental pathogens such as bacterial, fungal, viral, industrial chemical irritants and pollution and provides antiviral immunity. Mucosal damage or dryness makes it easier for the virus to enter the body. After the enemy entered the body and began to damage the cells, the production of interferons, which ensure their immunity to the action of the virus, is of great importance.

The mucous membrane of the upper respiratory tract is mostly covered with a thin specialized epithelium that creates a receptive (sensitive) barrier that is constantly bombarded by exogenous living or dead antigenic material.

The inhaled air contains a significant amount of potentially harmful substances (gases, suspended corpuscular particles, bacteria, viruses, mycoplasmas, fungi, including yeast, rickettsia, pollen, particles of desquamated epithelium of humans and animals, etc.). According to the concept of local immunity, mucous membranes and skin, as integuments facing the external environment, protect the internal environment of the body and maintain the constancy of the internal environment through the close interaction of an evolutionarily developed complex of nonspecific and specific defense mechanisms.

It is important to understand that ENT organs are no exception in terms of microbial sterility, i.e. Normally, we can detect certain microorganisms in the nose, throat, and outer ear. These microbes, in conditions of maintaining immune resistance, not only do not harm us, but, on the contrary, have a positive effect. They form the so-called biofilm (0.1 to 0.5 mm thick) - the polysaccharide framework of which, consisting of microbial polysaccharides and mucin, prevents the colonization of the body by pathogenic microorganisms.

The normal microflora of the pharynx is diverse, since the microflora of the oral cavity and the airways are mixed here. Representatives of the resident microflora are: Neisseria, diphtheroids, and hemolytic streptococci, enterococci, mycoplasmas, coagulase-negative staphylococci, moraxella, bacteroids, borrelia, treponema, actinomycetes. In the upper respiratory tract, streptococci and neisseria predominate, in addition, there are staphylococci, diphtheroids, hemophilic bacteria, pneumococci, mycoplasmas, and bacteroids. The mucous membrane of the larynx, trachea, bronchi is normally sterile.

It should be said that the above species spectrum of microorganisms is not unchanged. Its composition depends on many factors: concomitant pathology, age, environmental conditions, working conditions, nutrition, previous diseases, injuries and stressful situations, etc.

Conditions such as acute and chronic diseases of the whole organism, and especially the ear, throat, nose and mouth, allergies, adverse physical factors (hypothermia, insolation, etc.), chemical agents, physical, intellectual and psycho-emotional overstrain, taking antibacterial , hormonal and cytostatic drugs, malnutrition, hypovitaminosis, occupational hazards, smoking, alcohol provoke a violation of the normal microbiological balance in the ENT organs and are the causes of a violation of the qualitative and quantitative composition of the microflora of the oropharynx.

There is a bacteriological concept that characterizes a change in the ratio of representatives of normal microflora, a decrease in the number or disappearance of certain types of microorganisms due to an increase in the number of others and the appearance of microbes - this is dysbacteriosis.

Therapy of dysbacteriosis should be strictly individual and aimed primarily at eliminating the source of the problem. Inflammatory foci in the nasopharynx and oropharynx must be eliminated - carious teeth are treated, adenoid vegetations, palatine tonsils are sanitized, etc. Remember that they can not only cause local inflammatory and infectious processes and oropharyngeal dysbacteriosis, but also be a source of autoinfection and autointoxication of the whole organism.

Convincing data indicate that the occurrence of a number of diseases of the respiratory, gastrointestinal, cardiovascular systems, musculoskeletal system is due to focal infection in the oropharynx. Therefore, sanitation of the oral cavity and ENT organs is a prerequisite and the first step towards recovery in many pathological processes.