The main goal of microbiology is the study of living organisms that are not visible to the naked eye. Thanks to this area of science, a person has an idea about fungi, bacteria, parasites and viruses, about how they affect the environment and the human body. Over the centuries of experiments and analyzes, civilization has learned to use them for economic purposes, for example, for the preparation of sour-milk products, in industrial ones for the production of organic acids and alcohols, and medical ones. Despite this, the form of human interaction with the microscopic world is mutually beneficial. The best example of this is the commensalism of the organism and its contents - microflora.
In microbiology, the microflora of the human body is devoted to voluminous research, painstaking scientific work and thorough experiments. They are mainly aimed at studying the composition of certain organs, the influence of microorganisms on tissues, and the conditions for their reproduction. In the qualification works on the normal microflora of the human body, special attention is paid to diseases caused by microbes, and the establishment of normal quantities at which they are most harmless.
What it is?
The term "normal" microflora of the human body is most often used to refer to a set of microorganisms that live in a healthy body. Despite the botanical meaning of the word flora, the concept unites all the living creatures of the inner world. It is represented by a variety of bacteria, which are mainly concentrated on the skin and mucous membranes. Their features and action directly depend on the location in the body. And if an imbalance occurs in the microflora of the human body, then this is due to a disruption in the functioning of part of the body. The microscopic component has a significant effect on the anatomy, physiology, susceptibility to pathogens and the incidence of the host. In this, the main role of the microflora of the human body.
The human body, containing about 10 13 cells, normally contains about 10 14 bacteria. Depending on the age stages of human formation, the normal microflora of the body changes, but its components are relatively stable: certain bacteria inhabit the corresponding areas. Under normal functioning, microorganisms help the host, but in some cases pose a threat. Viruses and parasites are not considered members of the normal microflora of the human body in microbiology, because they are not commensals and do not bring benefit to the carrier. They are classified as pathogenic microorganisms.
Normal microflora in the human body
Depending on age, state of health and the environment, the normal microflora of the human body varies in definitions. To better understand how it is structured, what is caused by it and how it works, most studies are conducted on animals. Its components are microscopic organisms located throughout the body in specific areas. They get into the right environment even during the period of bearing the baby and are formed thanks to the microflora of the mother and medicines. After birth, bacteria enter the body as part of breast milk and artificial mixtures. The microflora of the environment and the human body are also connected, therefore, a favorable environment is the key to the development of normal microflora in a child. It is necessary to take into account the ecology, the purity of drinking water, the quality of household and hygiene items, clothing and food. Microflora can be completely different in people leading a sedentary and mobile lifestyle. She adapts to external factors. For this reason, an entire nation may have some kind of similarity. For example, the microflora of the Japanese contains an increased number of microbes that contribute to the processing of fish.
Its balance can be disturbed by antibiotics and other chemicals, which leads to infections due to the spread of pathogenic bacteria. The microflora of the human body is subject to constant changes and instability, because external conditions change, and the body itself also changes over time. In each area of the body, it is represented by special species.
Leather
Microbes spread depending on the type of skin. Its plots can be compared with regions of the Earth: forearms with deserts, scalp with cool forests, crotch and armpits with a jungle. The prevailing microorganism populations depend on the conditions. Hard-to-reach parts of the body (armpits, crotch and fingers) contain more microorganisms than more open areas (legs, arms and trunk). Their number also depends on other factors: the amount of moisture, temperature, and the concentration of lipids on the surface of the skin. Typically, toes, armpits, and the vagina are colonized by gram-negative bacteria more often than drier areas.
The microflora of human skin is relatively constant. The survival and reproduction of microorganisms partially depend on the interaction of the skin with the environment and partly on the characteristics of the skin. The specificity is that bacteria adhere better to certain epithelial surfaces. For example, when colonizing the nasal mucosa, staphylococci have an advantage over streptococci viridans, and vice versa, they are inferior to them in the development of the oral cavity.
Most microorganisms live on the surface layers and in the upper parts of the hair follicles. Some are deeper and not at risk from conventional disinfection procedures. They are a kind of reservoir for recovery after the removal of surface bacteria.
In general, gram-positive organisms predominate in the microflora of human skin.
- Epidermal staphylococcus. The most common, accounting for 90% of resident aerobic microflora.
- Staphylococcus aureus. The nose and perineum are the most common places for colonization. Its quantity changes with age, being large in newborns, smaller in adults. It is extremely common (80-100%) on the skin of patients with certain dermatological diseases, such as atopic dermatitis. The reason for this phenomenon is still unclear.
- Micrococci. Not as common as staphylococci and diphtheroids, but present on normal skin. Micrococci luteus is the predominant species, usually accounting for 20-80% of all.
- Difteroids. The term refers to a spectrum of microorganisms belonging to the genus Corynebacterium. They are divided into four groups: lipophilic and non-lipophilic; anaerobic dipteroids producing porphyrins; those associated with axillary trichomycosis (axillary hair infection). Lipophilic is extremely common in the armpit, while non-lipophilic is more common on smooth skin. Anaerobic dipteroids are most common in areas with sebaceous glands.
- Streptococcus Rarely found on normal skin. This is due to the presence of lipids on it, since these lipids are fatal to streptococci. Their other groups exist mainly in the mouth, from where they can rarely spread to the skin.
- Gram-negative bacilli. Given their huge number in the intestines and in the natural environment, their deficiency on the skin is striking. Dryness is the main factor preventing the growth of gram-negative bacteria on intact skin.
- Microflora of nails. Dust particles and other foreign matter can get under the nails and contribute to the growth of bacteria. Key representatives: aspergillus, penicillium, cladosporium and mucor.
Oral cavity
Variegated microbial flora develops here, and streptococcal anaerobes live in the cracks between the gums. The pharynx can be the place of entry and initial distribution for the neisseria, bordetella and streptococcus.
Oral flora directly affects dental caries and dental diseases, which affect about 80% of the population in the Western world. Anaerobes in the oral cavity are responsible for many of the brain, facial and lung infections, the formation of abscesses. The airways (small bronchi and alveoli) are usually sterile because particles the size of a bacterium do not reach them. In any case, they are confronted with host defense mechanisms, such as alveolar macrophages, which are not found in the pharynx and oral cavity.
Gastrointestinal tract
Intestinal bacteria play an important role in the development of the immune system, are responsible for exogenous pathogenic microorganisms. The flora of the colon consists mainly of anaerobes, which are involved in the processing of bile acids and vitamin K, contribute to the production of ammonia in the intestine. They can cause abscesses and peritonitis.
Gastric microflora is often changeable, and species populations do not grow due to the adverse effects of acid. Acidity reduces the number of bacteria, which increases after a meal (103-106 organisms per gram of content) and remains low after digestion. Some Helicobacter species are still able to inhabit the stomach and cause type B gastritis and peptic ulcer.
Rapid peristalsis and the presence of bile explain the small number of organisms in the upper gastrointestinal tract. Further, along the small and ileum, bacterial populations begin to increase, and in the ileocecal valve zone they reach 106-108 organisms per milliliter. In this case, streptococci, lactobacilli, bacteroids and bifidobacteria predominate.
A concentration of 109-111 bacteria per gram of contents can be found in the colon and feces. Their rich flora consists of almost 400 species of microorganisms, 95-99% of which are anaerobes. For example, bacteroids, bifidobacteria, eubacteria, peptostreptococci and clostridia. In the absence of air, they multiply freely, occupy accessible niches and produce metabolic waste products, such as acetic, butyric and lactic acids. Severe anaerobic conditions and bacterial waste are factors that inhibit the growth of other bacteria in the colon.
Although the microflora of the human body can resist pathogens, many of its representatives cause disease in humans. Anaerobes in the intestinal tract are the primary agents of abdominal abscesses and peritonitis. Intestinal breakdowns caused by appendicitis, cancer, heart attack, surgery, or gunshot wounds almost always affect the abdominal cavity and neighboring organs with normal flora. Antibiotic treatment allows some anaerobic species to become dominant and cause disorders. For example, clostridia difficile, which remain viable in a patient undergoing antimicrobial therapy, can cause pseudomembranous colitis. Other pathological conditions of the intestine or surgery contribute to bacterial growth in the upper thin section of the organ. Thus, the disease progresses.
Vagina
The vaginal flora changes with the age of a person, is regulated by vaginal pH and hormone levels. Transient microorganisms (e.g., candida) often cause vaginitis. Lactobacilli predominate in girls during the first month of life (vaginal pH is approximately 5). Glycogen secretion appears to cease from about the first month until puberty. During this time, diphtheroids, epidermal staphylococci, streptococci and Escherichia coli develop more actively (pH about 7). During puberty, glycogen secretion resumes, pH decreases, and women acquire an “adult” flora, in which there are more lactobacilli, corynebacteria, peptostreptococci, staphylococci, streptococci and bacteroids. After menopause, the pH rises again, and the composition of the microflora returns to that which is in adolescence.
Eyes
The microflora of the human body is almost absent in the eye area, although there are exceptions. Lysozyme, secreted with tears, can interfere with the formation of certain bacteria. Studies reveal rare staphylococci and streptococci, as well as hemophilus in 25% of samples.
What is the role of normal microflora in the human body?
The microscopic world directly affects the health status of the host. To study its influence, more fundamental research is needed than is currently being done. But the basic functions of the microflora of the human body have already been identified: supporting immunity and helping in vital processes, such as food processing.
Microorganisms are a source of vitamins and minerals; moreover, they neutralize the action of weak pathogens and poisons. For example, the intestinal flora takes part in the biosynthesis of vitamin K and other products that break down bile acids and produce ammonia. Another role of normal microflora in the human body is to control the appetite of the host. She tells you what the body needs and what to use to maintain balance. Bifidobacteria need protein food, E. coli - in vegetables and fruits. If a person himself does not know what he wants, this is a clear sign of a general insufficiency in the microflora. Frequent changes in diets and eating habits can damage her, even though she has the ability to rebuild. The environment and the normal microflora of the human body are also closely related.
Common pathologies
Violation of the surface of the mucous membrane often leads to infection of a person and damage to the normal microflora of the human body. Carious, periodontal diseases, abscesses, unpleasant odors and endocarditis are signs of infection. Deterioration of the state of the carrier (for example, due to heart failure or leukemia) can lead to the fact that the normal flora will not suppress transient pathogens. The microflora of the human body in norm and pathology varies significantly, this is a decisive factor in determining the health of the owner.
Bacteria can cause many different infections of varying severity. For example, Helicobacter pylori is a potential pathogen of the stomach, as it plays a role in ulcer formation. According to the principle of infection, bacteria can be divided into three main groups:
- Primary pathogens. They are the causative agents of the disorder, being isolated from the patient (for example, when the cause of diarrheal disease lies in the laboratory isolation of salmonella from feces).
- Opportunistic pathogens. They harm patients at risk due to their predisposition to disease.
- Non-pathogenic agents (Lactobacillus acidophilus). However, their category may change due to the high adaptability and the harmful effects of modern radiation therapy, chemotherapy and immunotherapy. Some bacteria that were not previously considered pathogens now cause disease. For example, Serratia marcescens is a soil bacterium that causes pneumonia, urinary tract infections, and bacteremia in infected hosts.
Man is forced to live in an environment filled with a variety of microorganisms. Due to the scale of the problem of infectious diseases, the desire of physicians to understand the natural immune mechanisms of the carrier is justified. Huge research efforts are being spent to identify and characterize virulence factors of pathogenic bacteria. The availability of antibiotics and vaccines provides doctors with powerful tools to control or treat many infections. But, unfortunately, these drugs and vaccines have not yet completely eradicated bacterial diseases in humans or animals.
The basis of human health is the normal microflora of the human body, its function is to protect against pathogens and support the host's immunity. But, she herself needs care. There are some tips on how to ensure internal balance in the microflora and avoid trouble.
Prevention and treatment of dysbiosis
To maintain the microflora of the human body, microbiology and medicine are advised to adhere to elementary rules:
- Observe hygiene.
- Lead an active lifestyle and strengthen the body.
- Get vaccinated against infectious diseases and beware of antibiotics. Complications may occur (yeast infections, skin rashes, and allergic reactions)
- Eat properly and add probiotics to your diet.
Probiotics are good bacteria in fermented foods and supplements. They strengthen the friendly bacteria in the intestines. For relatively healthy people, it is always useful to eat primarily natural food, and only then supplements.
Prebiotics are another necessary component of food. They are found in whole grains, onions, garlic, asparagus and chicory roots. Regular use reduces intestinal irritation and soothes allergic reactions.
In addition, nutritionists advise to avoid fatty foods. According to studies in mice, fats can damage the intestinal membrane. As a result, unwanted chemicals released by bacteria enter the bloodstream and inflame nearby tissues. Moreover, some fats increase populations of hostile microorganisms.
Another useful skill is the control of personal experiences and stress. Stress affects the functioning of the immune system - either by suppressing or enhancing responses to pathogens. And in general, mental distress eventually turns into physical ailments. It is important to learn how to identify the origins of problems before they cause irreparable harm to the health of the body.
The internal balance, the normal microflora of the human body and the environment are the best that can be provided for health.