The functions of the normal microflora of the oral cavity. The successes of modern natural science

Date: 04.03.2020

Oral microflora.

There are more different types of bacteria in the oral cavity than in the rest of the gastrointestinal tract, and this number, according to different authors, ranges from 160 to 300 species. This is due not only to the fact that bacteria enter the oral cavity with air, water, food - the so-called transit microorganisms, whose residence time is limited. Here we are talking about a resident (permanent) microflora, which forms a rather complex and stable ecosystem of the oral cavity. These are nearly 30 microbial species. Under normal conditions (antiseptic pastes, antibiotics, etc. are not used), changes in the existing ecosystem occur depending on the time of day, year, etc., and only in one direction, that is, only the number of representatives of different microorganisms changes. However, the species representation remains constant for a particular individual during, if not the entire life, then over a long period. The composition of the microflora depends on salivation, the consistency and nature of food, as well as on the hygienic content of the oral cavity, the state of tissues and organs of the oral cavity and the presence of somatic diseases.
Disorders of salivation, chewing and swallowing always lead to an increase in the number of microorganisms in the oral cavity. Various anomalies and defects that make it difficult to flush out microorganisms with a current of saliva (carious lesions, poor-quality dentures, etc.), contribute to an increase in their number in the oral cavity.
The microflora of the oral cavity is extremely diverse and includes bacteria (spirochetes, rickettsiae, cocci, etc.), fungi (including actinomycetes), protozoa, viruses. At the same time, anaerobic species constitute a significant part of the microorganisms in the oral cavity of adults. According to various authors, the content of bacteria in the oral fluid ranges from 43 million to 5.5 billion in 1 ml. The microbial concentration in dental plaques and the gingival groove is 100 times higher - about 200 billion microbial cells per 1 g of the sample (which contains about 80% water).

The largest group of bacteria constantly living in the oral cavity are cocci - 85 - 90% of all species. They have significant biochemical activity, decompose carbohydrates, break down proteins to form hydrogen sulfide.
Streptococci are the main inhabitants of the oral cavity. 1 ml of saliva contains up to 109 streptococci. Most streptococci are facultative (non-strict) anaerobes, but there are obligate (strict) anaerobes - peptococci. Streptococci ferment carbohydrates by the type of lactic acid fermentation with the formation of significant amounts of lactic acid and other organic acids. The acids formed as a result of the vital activity of streptococci inhibit the growth of some putrefactive microorganisms, staphylococci, Escherichia coli, typhoid and dysentery sticks that enter the oral cavity from the external environment.
Staphylococci are also present in dental plaque and on the gums of healthy people - Staph. epidermidis, however, some people may have Staph. aureus.
Rod-shaped lactobacilli in a certain amount constantly live in a healthy oral cavity. Like streptococci, they produce lactic acid, which inhibits the growth of putrefactive and some other microorganisms (staphylococci, E. colli, typhoid and dysentery sticks). The number of lactobacilli in the oral cavity with dental caries increases significantly. To assess the "activity" of the carious process, the "lactobacillus test" (determination of the number of lactobacilli) was proposed.
Leptotrichia also belong to the family of lactic acid bacteria and are the causative agents of homofermentative lactic acid fermentation. Leptotrichia are strict anaerobes.
Actinomycetes (or radiant fungi) are almost always present in the oral cavity of a healthy person. Outwardly, they are similar to filamentous fungi: they consist of thin, branching filaments - hyphae, which, intertwining, form the mycelium visible to the eye.
In the oral cavity of healthy people, yeast-like fungi of the genus Candida (C. albicans, C. tropicalis, C. crusei) are found in 40-50% of cases. Pathogenic properties are most pronounced in C. albicans. Yeast-like fungi, multiplying intensively, can cause dysbacteriosis, candidiasis, or local damage to the oral cavity (thrush) in the body. These diseases arise as a result of uncontrolled self-treatment with broad-spectrum antibiotics or strong antiseptics, when fungal antagonists from representatives of the normal microflora are suppressed and the growth of yeast-like fungi resistant to most antibiotics is enhanced (antagonists are some representatives of the microflora that suppress the growth of other representatives) .
Spirochetes populate the oral cavity from the moment the baby teeth erupt in a child and from that time on they become permanent inhabitants of the oral cavity. Spirochetes cause pathological processes in association with fusobacteria and vibrios (ulcerative stomatitis, Vincent's angina). Many spirochetes are found in periodontal pockets during periodontitis, in carious cavities and in dead pulp.
In half of healthy people, protozoa can live in the mouth, namely Entamoeba gingivalis and Trihomonas. Most of them are found in dental plaque, purulent contents of periodontal pockets with periodontitis, with gingivitis, etc. They multiply intensively with unhygienic maintenance of the oral cavity.
The normal microflora of the oral cavity is quite resistant to the action of antibacterial factors of the oral fluid. At the same time, it itself participates in the protection of our body from microorganisms coming from outside (its normal microflora suppresses the growth and reproduction of pathogenic "aliens"). The antibacterial activity of saliva and the number of microorganisms living in the oral cavity are in a state dynamic balance. The main function of the antibacterial system of saliva is not to completely suppress the microflora in the oral cavity, but to control its quantitative and qualitative composition.

When isolating microorganisms from different zones of the oral cavity of adults, the predominance of certain species in different areas was noted. If you divide the oral cavity into several biotopes, the following picture will appear. Due to its vastness, the mucous membrane has the most variable composition of microflora: on the surface, gram-negative anaerobic flora and streptococci are predominantly allocated. Obligate anaerobes predominate in the sublingual folds and crypts of the mucous membrane. Streptococci and corynebacteria are found on the mucous membrane of the hard and soft palate.

As the second biotope, the gingival groove (groove) and the liquid in it are isolated. There are Bacteroids (B. melaninogenicus), Porphyromonas (Porphyromonas gingivalis), Prevotella intermedia, as well as actinobacillus actinomycetemcomitans (Actinibacillus actinomicitemcomitans), yeast-like fungi and other mycoplasma and mycoplasma

The third biotope is dental plaque - this is the most massive and diverse bacterial accumulation. The number of microorganisms is from 100 to 300 million in 1 mg. The species composition is represented by almost all microorganisms with a predominance of streptococci.

Oral fluid should be named as the fourth biotope. Through it, the relationship between all other biotopes and the organism as a whole is carried out. Significant quantities in the oral fluid contain veilonella, streptococci (Str. Salivarius, Str. Mutans, Str. Mitis), actinomycetes, bacteroids, filamentous bacteria.

Thus, the microflora of the oral cavity is normally represented by various types of microorganisms. Some of them are associated with diseases such as tooth decay and periodontitis. Microorganisms are involved in the occurrence of these most common ailments. Experimental studies on animals have shown that the presence of microorganisms is a mandatory factor for the development of caries (Orland, Blaynay, 1954; Fitzgerald, 1968.) The introduction of streptococci into the oral cavity of sterile animals leads to the formation of a typical dental carious lesion (FFitzgerald, Keyes, 1960; Zinner, 1967). However, not all streptococci are equally capable of causing tooth decay. It has been proven that Streptococcus mutans has an increased ability to form plaque and cause damage to the teeth, the colonies of which account for up to 70% of all microorganisms of plaque.

For the development of inflammatory periodontal diseases, the main condition is also the presence of an association of microorganisms, such as Actinibacillus actinomicitemcomitans, Porphyromonaas gingivalis, Prevotella intermedia, as well as streptococci, bacteroids, etc. Moreover, the occurrence and intensity of pathological processes directly depends on the qualitative and quantitative composition of dental plaque microflora plaques (see table).

As follows from the above facts, caries and inflammatory diseases of the oral cavity occur when the normal balance between its own and foreign microflora is disturbed. Therefore, hygiene products with antibacterial components should be aimed at maintaining the constancy of microflora at the physiological level, that is, when there is no shift in the quantitative and qualitative composition of microorganisms in favor of pathogenic ones throughout the entire period of the organism's life.

The most harmful bacteria in the mouth is Streptococcus mutans, which produces lactic acid. In October 2002, employees of the National Institute of Dental and Craniofacial Research in Bethesda, Maryland (USA), completely isolated its chromosome series: 1900 villain genes!

Porphyromonas gingivalis, which causes the development of periodontitis, was isolated only in 2001!

The species composition of the oral microflora is normally quite constant, however, the number of microorganisms varies significantly depending on salivation, consistency and nature of food, as well as on the hygienic content of the oral cavity, the state of tissues and organs of the oral cavity and the presence of somatic diseases.

Thus, saliva does not destroy the microflora in the oral cavity, but ensures its quantitative and qualitative constancy.

The most important source of antibacterial activity of saliva is leukocytes migrated into the oral cavity. Neutrophilic leukocytes caught on the surface of the mucous membrane retain the ability to phagocytosis. In addition, the oral fluid contains antibacterial substances produced by T- and B-lymphocytes, which migrate through the lymphatic pharyngeal ring.

Humoral and cellular antibacterial defense factors are closely related. A number of components of saliva - the enzyme oxidase, salivary kallikrein and kinins formed with its participation - have a pronounced chemotactic activity, ensuring the regulation of the migration of leukocytes in the oral cavity. In addition to the chemotactic action, kinins also promote the migration of leukocytes by increasing the vascular permeability of the tissues of the oral cavity. Nonspecific antibacterial protection of the oral cavity is provided by enzymes secreted mainly by the salivary glands and released by migrated leukocytes: lysozyme, RNase, DNase, peroxidase. It is necessary to point out the extremely wide spectrum of antibacterial activity of these enzymes, which suppress the growth of bacteria, viruses, fungi and protozoa.

The oral fluid has coagulating properties due to the presence of a number of factors of the coagulant and fibrinolytic systems in it. These properties play an important role in ensuring local homeostasis, cleaning the oral cavity, developing inflammatory, regenerative and other processes.

Thromboplastin, and antique tissue, antiheparin substance, factors included in the prothrombin complex, fibrinase, etc. were also found in the oral fluid.

Literature:

A. P. Bezrukova Periodontics. M., 1999. from. 67-74
Borovskiy E.V., Leontiev V.K. Biology of the oral cavity. N. Novgorod, 2001
Doc. MUDr Ivo Drizhal, Csc. Modern ideas about dental plaque // New in dentistry, No. 10, 2001. P. 23-38
Microbial flora of the oral cavity: ways of colonization, distribution, distribution by biotopes of the oral cavity in health and disease // Dental Review, No. 1, 2004. P. 7-10

Introduction

It is believed that the oral cavity- it is one of the dirtiest places in the entire human body. One can argue with this statement, but, according to scientists, in saliva and oral fluid, on average, there are 109 microorganisms in 1 milliliter, and in dental plaque- 1011 in 1 gram. According to the latest data, 688 species of various bacteria do not live in the mouth of a person who does not suffer from pathologies of the oral cavity organs.

Despite such a variety of microbiota, with good hygiene and the absence of somatic diseases and mental disorders (such as diabetes, AIDS, constant stress and many others), we live in peace and harmony with the colonizers of the mucous membranes of our oral cavity. The manifestation of the presence of certain microorganisms in the oral cavity can serve as a diagnostic sign (for example, fungal diseases of the mucous membrane can be a sign of violations of the T-cell link of immunity).

But, in addition to the mucous membranes, microorganisms also colonize the surface of the hard tissues of the tooth. As everyone knows, this leads to caries, and if you postpone the visit to the dentist and let the process take its course- to complications such as pulpitis, periodontitis, and later- to the formation of granulomas and cysts.Knowledge about the presence of certain representatives of the microworld in the oral cavity, as well as about their physiological characteristics, allows one to find new ways to combat the pathologies that they can cause.The study of the oral microbiome has not lost its relevance today. Periodically, there are reports of the discovery of new representatives or the decoding of the genomes of previously found bacteria. All this is necessary for a deeper understanding of the pathogenesis of diseases of the oral cavity organs, the study of interbacterial interactions and the improvement of the processes of treatment and recovery of patients, as well as the prevention of local and generalized complications.

Normal oral microbiota

As already mentioned, a large number of different types of bacteria are normally found in the human oral cavity, which do not live in isolation, but enter into various interactions, for example, form biofilms. The entire microbiome of the oral cavity can be conditionally divided into two groups: permanent (species specific to a given biotope) and non-permanent microorganisms (immigrants from other host biotypes, for example, the nasopharynx, intestines). There may also be a third type of microorganism - alien microbiota from the environment.

Among the representatives of normal microbiota, various types of actinomycetes can be distinguished (Actinomyces cardiffensis, A. dentalis, A. oris, A. odontolyticus, etc.), representatives of the genus Bacteroidetes (taxa 509, 505, 507, 511, etc.), Bifidobacterium (B. dentium, B. longum, B. breve, etc.), Campylobacter (C. gracilis, C. gingivalis, C. sputorum, etc.), Fusobacterium (F. periodonticum, F. gonidiaformans, F. hwasookii, etc.), Staphylococcus (S. warneri, S. epidermidis, etc.), Streptococcus (St. mutans, St. intermedius, St. lactarius, etc.) With all its diversity, the species composition of the oral microbiota is fairly constant, but the number of microbes of different species can fluctuate due to their species and changing environmental conditions. The quantitative composition of the microbiota can be influenced by:

1) the condition of the oral mucosa,
2) physical conditions (temperature, pH, etc.),
3) the secretion of saliva and its composition,
4) the condition of the hard tissues of the teeth,
5) food composition,
6) hygienic condition of the oral cavity,
7) the absence of pathologies of the salivary glands, the function of chewing and swallowing,
8) the natural resistance of the body.

Bacteria are retained on the surface of hard and soft tissues due to their morphological features and certain intercellular interactions, which will be described below. Different types of bacteria have affinity for different tissues. For a further story about the formation of oral biofilms and the development of pathological processes, it is necessary to consider the main features of the prevailing microorganisms.

Staphylococci

This genus of bacteria is represented by motionless gram-positive cocci, located in the smear "grape bunches"; are facultative anaerobes, chemoorganotrophs. The most common representative of this genus in the oral cavity is Staphylococcus epidermidis, which is mainly located on the gums and in dental plaque. Breaks down food debris in the mouth, participates in the formation of dental plaque. Another common representative, Staphylococcus aureus, is the cause of the development of purulent bacterial infections, including generalized ones.

Streptococci

They are found in the oral cavity much more often than any other bacteria. Gram-positive spherical or ovoid cocci, chemoorganotrophs, facultative anaerobes. The representatives of the genus living in the oral cavity were allocated to a separate group of oral streptococci. Like staphylococci, they break down food residues (mainly carbohydrates) to form hydrogen peroxide, as well as lactic acid, which plays an important role in the formation of dental plaque. Streptococcus mutans and S. sangius live mainly on the hard tissues of the teeth and are found only after damage to the enamel, S. salivarius- mainly on the surface of the tongue.

Waylonella

Gram-negative anaerobic non-spore-forming cocci, chemoorganotrophs. In the course of their vital activity, they decompose lactate, pyruvate and acetate to carbon dioxide and hydrogen, which increases the pH of the environment and has a positive effect on the formation of dental plaque (mainly Veillonella parvula) and the growth of other microorganisms. In addition, they are capable of oxidizing food residues to various organic acids, which contributes to the processes of demineralization and the formation of micro cavities.

Lactobacillus

Lactic acid bacteria, gram-positive bacilli, facultative anaerobes. Distinguish between homoenzyme (they form only lactic acid during the decomposition of carbohydrates) and heteroenzyme species (form lactic, acetic acid, alcohol and carbon dioxide). The formation of a large amount of acids, on the one hand, has an inhibitory effect on the growth of other microbes, and on the other hand, it contributes to the demineralization of the enamel.

Actinomycetes

Lower actinomycetes, inhabitants of the oral cavity and intestines. Their feature is the ability to form a branching mycelium. According to Gram, they are colored positively. Strict anaerobes, chemoorganotrophs. In the process of life, carbohydrates are fermented to form acids (acetic, lactic, formic, succinic). The most favorite place- area of \u200b\u200binflamed gums, decayed roots of teeth, pathological gum pockets. Actinomyces israelii is present on the gum surface, in plaque, carious dentin, and in dental granulomas.

Dental plaque

The above microorganisms live in the oral cavity on a permanent basis. With an insufficient level of hygiene, we can observe the result of their vital activity: the formation of plaque, tartar, caries, periodontitis, gingivitis. The most common dental hard tissue disease- caries. To understand who is to blame and what to do, it is necessary to take a closer look at what any caries begins with.

The key mechanism behind tooth decay is plaque formation. At its core, a plaque- it is an accumulation of a large number of various bacteria that consume and produce organic matter. They form a multi-layer conglomerate, each layer in which has its own function. It turns out a small “city” or “country” where there are “workers” producing acids and vitamins (streptococci, corynobacteria, etc.), there are transport routes along which nutrients are delivered to different layers of the microcommunity, there are “border guards” who are on the periphery and protect our city-country from collapse under the influence of external factors (actinomycetes).

The plaque formation process begins immediately after you brush your teeth. A film forms on the enamel surface- pellicle, which consists of components of saliva and gingival fluid (albumins, immunoglobulins, amylase and lipids). Despite the fact that the outer surface of the tooth has a smoothed relief, there are convex and concave areas on it, which correspond to the ends of the enamel prisms. It is to them that the first bacteria attach. Within 2‒ For 4 hours, bacteria colonize the pellicle, but they are weakly bound to the film and are easily removed. If during this time no one stopped them, they begin to actively grow and multiply, form microcolonies.

Streptococci (S. mutans and S. sanguis) are the first to colonize enamel. The morphological features of their cells, as well as the presence of micropores and irregularities on the enamel, help them to attach to the surface of the tooth. They synthesize lactic acid from sucrose, which contributes to the creation of an acidic environment and demineralization of the enamel. Bacteria are fixed in the recesses of the tooth (which is why the most common type of caries- this is caries of the chewing surfaces of molars and premolars- due to the presence of pronounced fissures on them) and lend a helping hand to those who themselves are not able to gain a foothold on the enamel. This phenomenon is called coaggregation. The most common example is S. mutans, which has special receptors for adhesion on the enamel and which synthesizes extracellular polysaccharides from sucrose, which facilitates the binding of streptococci to each other and the attachment of other bacteria to the enamel.

During the first 4 hours, streptococci are joined by veilonella, corynebacterium, actinomycetes. As the number of anaerobic bacteria increases, the amount of lactic acid increases. Veilonella ferment acetic, pyruvic and lactic acids well; in these areas, an increase in pH occurs, contributing to the accumulation of ammonia in soft dental plaque. Ammonia and the resulting dicarboxylic acids actively combine with magnesium, calcium and phosphate ions, forming crystallization centers. Corinebacteria synthesize vitamin K, which stimulates the growth of anaerobic bacteria. Actinomycetes form intertwining threads and contribute to the adhesion of other bacteria to the enamel, form a dental plaque framework, and also produce acids, contributing to the demineralization of the enamel. The listed bacteria make up the “early” plaque.

“Dynamic” plaque that forms within 4‒ 5 days, mainly consists of fusobacteria, veilonella and lactobacilli. Fusobacteria produce powerful enzymes and, together with spirochetes, play a role in the development of stomatitis. Lactobacilli abundantly synthesize lactic and other acids, as well as vitamins B and K.On the 6th day, a mature dental plaque is formed, which mainly consists of anaerobic rods and actinomycetes. This process takes place even with a stable two-time daily oral hygiene. The fact is that most adults (and even more so children) do not know how to properly brush their teeth. Usually, some parts of the dentition are well and thoroughly cleaned, and some remain intact and not cleared of plaque. Most often, a mature plaque (and then tartar) forms on the lingual side of the incisors of the lower jaw.

Once in the biofilm, bacteria begin to work together. The colonies in the microbiocenosis are surrounded by a protective matrix, which is permeated by channels and, in essence, is the very transport routes that were mentioned above. Along these paths, not only nutrients circulate, but also waste products, enzymes, metabolites and oxygen.

Microorganisms in a biofilm are linked not only through a framework (extracellular matrix), but also through intercellular interactions. Due to their commonness, bacteria become more resistant to antibiotics and the body's defense systems, begin to synthesize substances unusual for them and acquire new forms to maintain the stability of the biofilm.In a multicellular organism, the coherence of cell behavior is provided by special control systems (for example, the nervous system). In a group of separate independent organisms, there are no such centralized control systems, therefore, coordination of actions is ensured in other ways, including with the help of a sense of quorum- the ability of bacteria in biofilms to coordinate their behavior through the secretion of molecular signals.

For the first time, the sense of quorum was described in the marine bacterium Photobacterium fisheri. It is based on a signaling mechanism, which is carried out by the secretion of specific chemicals by bacteria at a high population density that interact with receptor regulatory proteins. Quorum sense systems assess not only population density, but also other parameters of the external environment through appropriate gene regulators. The quorum plays a key role in the regulation of many metabolic processes in microorganisms (bioluminescence in marine bacteria, stimulation of the growth of streptococci, synthesis of antibiotics, etc.).

Some recent research has shown that in addition to traditional cell-to-cell communication systems such as quorum, bacteria can use a stream of electrons to communicate. Within communities of bacterial biofilms, ion channels conduct long-range electrical signals due to spatially distributed waves of potassium, which depolarizes neighboring cells. Spreading through the biofilm, this depolarization wave coordinates metabolic states among cells within and at the periphery of the biofilm. This form of electrical communication can thus enhance metabolic codependency of a wide range in biofilms. Interestingly, due to the rapid diffusion of potassium ions in the aquatic environment, it is possible that even physically disconnected biofilms can synchronize their metabolic fluctuations through a similar exchange of potassium ions.

So, working together, the microorganisms that form plaque and plaque increase the likelihood of developing tooth decay. This happens for several reasons. First, cariogenic microorganisms are capable of producing hyaluronidase, which affects the permeability of the enamel. Secondly, bacteria are able to synthesize enzymes that break down glycoproteins. Thirdly, organic acids, which are formed as a result of the metabolism of bacteria, also contribute to the demineralization of the enamel, which helps bacteria penetrate deeper into the enamel (and then into the dentin), and also increases the roughness of the enamel, which leads to the "attachment" of new microorganisms.

After 12 days, the plaque mineralization process begins. Calcium phosphate crystals are deposited within plaque and bind tightly to the enamel surface. At the same time, bacteria continue to accumulate on the surface of the formed calculus, contributing to its growth. About 70- 90% of tartar - these are inorganic substances: 29- 57% calcium, 16 - 29% inorganic phosphate and about 0.5% magnesium. There are trace amounts of lead, molybdenum, silicon, aluminum, strontium, cadmium, fluorine and other chemical elements. Inorganic salts bind to proteins, the content of which in hard dental deposits is 0.1‒ 2.5%. Various amino acids are also found in tartar: serine, threonine, lysine, glutamic and aspartic acids, etc. Glutamate and aspartate are able to bind calcium ions, and the residues of serine, threonine and lysine- phosphate ions, which is very important for the initiation of plaque mineralization and further formation of dental calculus.

Interestingly, according to recent studies, unlike dental plaque, tartar inhibits the process of enamel demineralization and protects the tooth from the development of carious lesions.

In a 2016 study, it was found that out of 1,140 extracted teeth that had tartar, only one tooth had caries underneath hard deposits. Tartar delay in proximal caries was also found in one tooth out of 187 samples. On the distal surface of the upper jaw premolar, hard mineralized deposits penetrated into the carious cavity and filled the focus of initial demineralization, stopping the further development of caries. For comparison: on the mesial surface of the tooth, on which there were no hard dental deposits, extensive carious lesions were found extending through the enamel into the depths of dentin. The reasons for this effect of calculus on the spread of calculus have not yet been studied.The presence of soft and hard dental deposits has not only local, but also generalized consequences, which will be discussed below.

Odontogenic infection and its complications

A feature of most dental diseases is that they do not have a specific pathogen. In the process of development of odontogenic infection, the microbiocenosis of the oral cavity changes.

Typically, odontogenic infection begins with tooth decay. Due to the active vital activity of dental plaque bacteria, superficial caries turns into medium, medium- into deep, and deep caries turns into pulpitis. The pulp is located in the coronal and root parts of the tooth, therefore, coronal pulpitis is released, which then passes into the root. Going down the root canal, bacteria are able to escape through the apical opening of the tooth and enter the periodontal tissue. This process can occur both due to untreated caries and due to an error in endodontic treatment.- removal of the filling material by the apex of the tooth.

The resulting periodontitis is most often complicated by periostitis. Periostitis- This is an inflammation of the periosteum, in which the area of \u200b\u200bthe primary inflammatory process is limited to the causative tooth.

Among the complications, odontogenic osteomyelitis is also distinguished.- a process that extends beyond the periodontium of the causative tooth, and which, in turn, is the cause of the formation of abscesses and phlegmon of the soft tissues of the head and neck.

The microbiome in odontogenic infection includes various microorganisms that determine the type of exudative inflammation:

– greening and non-hemolytic streptococci, enterococci are more common with serous inflammation;
– Staphylococcus aureus and hemolytic streptococci cause purulent inflammation;
– peptostreptococci, veilonella, bacteroids and other bacteria with pronounced proteolytic properties are more often excreted during the putrefactive process.

With pulpitis, anaerobic representatives of the microcosm are mainly found, but putrefactive bacteria can also be detected. In the case of acute purulent periodontitis, staphylococcal associations prevail, serous- streptococcal. During the transition from acute to chronic inflammation, the composition of the prevailing microbiota changes.Due to the abundant blood supply to the maxillofacial region, bacteria from the oral cavity can enter the systemic circulation and spread throughout the body (and vice versa- this partially explains the presence of allochthonous microorganisms).

According to a 2014 study, the presence of tartar can be a risk of death from myocardial infarction. Previously, cases of the occurrence of foci of atherosclerosis on the carotid artery were described, which arose in connection with progressive periodontal disease. The fact is that dental plaque can be both supra- and subgingival. Supragingival dental deposits are mainly responsible for caries, and subgingival- periodontal disease. A large number of calculi can provoke the development of chronic inflammation in the oral cavity, which, in turn, can lead to the activation of systemic inflammatory reactions. They are involved in the development of atherosclerosis, which can ultimately lead to myocardial infarction and death.

In addition to the effects on the cardiovascular system, odontogenic infections can cause the development of such a generalized complication as sepsis. This complication can occur in the presence of an abscess, phlegmon, or secondary infectious foci, from which, against the background of severe immunosuppression, microorganisms continuously or periodically enter the vascular bed.

Sepsis - this is a rather formidable complication, which even today can lead to death. In 2007, a clinical case of odontogenic sepsis was published, the outcome of which was the death of the patient. Death from odontogenic sepsis- a rare occurrence, but in the presence of concomitant pathologies (for example, leukemia, as in the mentioned clinical case), there is still a risk of death. Even with the correct medical tactics (surgical operation, drainage of the focus, prescription of antibiotics) in immunosuppressive conditions, toxic and bacteremia can lead to the death of the patient within the next 24 hours after the operation.

Odontogenic infection can lead to the development of a systemic inflammatory response syndrome of the body, the main symptoms of which are: an increase in temperature to 38o C, tachycardia (up to 90 beats per minute), tachypnea (up to 20 breaths per minute), leukocytosis (up to 12000 / μl), leukopenia (up to 4000 / μl) or a shift of the leukocyte count to the left. The main cause of death in this syndrome is sepsis (55% of cases), as well as multiple organ failure (33%), upper airway obstruction (5%) and complications after anesthesia (5%).

Airway obstruction is a very common complication. It occurs with phlegmon of the deep regions of the mouth and neck (for example, with Ludwig's angina), as well as the root of the tongue. The danger of this complication lies in the fact that the supply of oxygen to the lungs (and therefore to the body as a whole) is disrupted, and to prevent the occurrence of severe tissue hypoxia (primarily of the brain), it is necessary to perform intubation or, in cases with extensive phlegmon of deep spaces, tracheostomy.

Purulent inflammation of the mediastinal tissue- mediastinitis - one of the most dangerous complications of a widespread odontogenic infection. Through the mediastinum, infection can enter the lungs, causing pleurisy, lung abscesses and destruction of lung tissue, and also move to the pericardium, causing pericarditis.

When the infection spreads not downward (to the neck and internal organs of the chest and abdominal cavities), but upward (to the face and the vault of the skull), complications such as acute maxillary sinusitis, cavernous sinus thrombosis and meningoencephalitis may occur. In 2015, a clinical case of multiple brain abscesses associated with odontogenic sepsis was published.

As mentioned at the very beginning of this chapter, odontogenic infections are mostly mixed. This means that bacteriological research reveals both anaerobic and aerobic microorganisms in crops. Different antagonistic and synergistic relationships occur between different groups of bacteria, which significantly aggravates the clinical picture of the disease.

In addition to the case of myocardial infarction described above, there is a high risk of developing endocarditis in patients who are at risk: with an artificial valve, a history of endocarditis, congenital heart defects, or who are recipients of heart transplants with valvular diseases.

Conclusion

All of the above facts indicate that it is extremely important for the patient to periodically visit the dentist and carry out primary, secondary and tertiary prevention of caries (that is, to prevent the occurrence of caries, its recurrence, as well as, if necessary, restore the patient's dental status and maintain chewing function). The doctor is obliged to be vigilant in working with patients with concomitant pathologies, if necessary, prescribe antibiotics (for example, patients with artificial heart valves) and follow the rules of asepsis and antiseptics. When abscesses and phlegmon appear, it is extremely important to carry out an operation as soon as possible to drain the infectious focus and remove the causative tooth to prevent the further development of generalized complications (sepsis), as well as secondary infectious foci.

But we must remember that the very colonizers of our mucous membranes not only lead to various infectious diseases, but are also normal representatives of the oral cavity. Carrying out complex interactions with each other and with representatives of the alien microbiota, microorganisms maintain homeostasis, are symbionts (for example, they reduce the risk of caries formation during calcification of dental plaque). The influence of resident microorganisms in the oral cavity on local pathological processes and on the body as a whole is still a subject of study, which means that many new discoveries await us.

Editor: Sergey Golovin, Maxim Belov

Images: Cornu Ammonis, Katerina Nikitina

List of references

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M. M. Solovyov, O. P. Bolshakov, D. V. Galetskiy "Purulent-inflammatory diseases of the head and neck", 2016
L. Carter, E. Lowis "Death from overwhelming odontogenic sepsis: a case report", 2007
Rishi Kumar Bali, Parveen Sharma "A review of complications of odontogenic infections", 2016.
T. Clifton, S. Kalamchi "A case of odontogenic brain abscess arising from covert dental sepsis", 2015
TP Vavilova "Biochemistry of tissues and fluids of the oral cavity: a tutorial", 2008
Mary L. Windle "Antibiotic Prophylactic Regimens for Endocarditis", 2016

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Introduction

The human body has several cavities - formations bounded by bone and soft tissue structures, which have a free volume, filled (partially or completely) with gases or liquids. These include the abdominal cavity, which lines the inner surface of the abdomen, contains a special liquid and gas environment, the pleural cavity, which is similar in structure and content; the cavity of the outer and inner ear, the cavity of the osteoarticular spaces, the cavity of the bladder and renal pelvis, the cavity of the nose, pharynx and mouth, the cavity of the neural spaces, etc.

A feature of all these cavities is the presence of a free space, unoccupied by biological tissue, usually containing a certain biological fluid.

The main purpose of all cavities is to provide specific mobility of organs, to create reliable isolation of some organs from others, to create a gradual connection and, at the same time, to isolate the external from the internal environment, to provide the most biological conditions for the functioning of the internal and external organs of the body.

1. The microflora of the oral cavity

The originality and peculiarity of the oral cavity is that, firstly, through it and with its help, two vital functions of the human body are carried out - respiration and nutrition, and secondly, that it is constantly in contact with the external environment. The mechanisms functioning in the oral cavity are under constant double influence - the influence of the organism on the one hand, and the external environment on the other.

Thus, a prerequisite for the correct assessment of the detected changes is a very clear idea of \u200b\u200bthe “norm”, that is, those parameters of the functional mechanisms of the oral cavity that do not depend on pathological processes, but are explained by the geno- and phenotypic characteristics of the organism. One of the most informative indicators is the oral microflora.

The oral cavity, its mucous membrane and the lymphoid apparatus play a unique role in the interaction of the organism with the surrounding world of microbes, between which complex and contradictory relations have been formed in the course of evolution. Therefore, the role of microorganisms is far from unambiguous: on the one hand, they are involved in the digestion of food, have a great positive effect on the immune system, being powerful antagonists of pathogenic flora; on the other hand, they are the causative agents and main culprits of major dental diseases.

Disorders of salivation, chewing and swallowing always lead to an increase in the number of microorganisms in the oral cavity. Various anomalies and defects that make it difficult to wash out microorganisms with a current of saliva (carious lesions, low-quality dentures, etc.), contribute to an increase in their number in the oral cavity.

The microflora of the oral cavity is extremely diverse and includes bacteria (spirochetes, rickettsia, cocci, etc.), fungi (including actinomycetes), protozoa, viruses. At the same time, anaerobic species constitute a significant part of the microorganisms in the oral cavity of adults. According to various authors, the content of bacteria in the oral fluid ranges from 43 million to 5.5 billion in 1 ml. The microbial concentration in dental plaques and the gingival groove is 100 times higher - about 200 billion microbial cells in 1 g of the sample (which contains about 80% water).

Streptococci are the main inhabitants of the oral cavity. 1 ml of saliva contains up to 109 streptococci. Most streptococci are facultative (non-strict) anaerobes, but there are obligate (strict) anaerobes - peptococci. Streptococci ferment carbohydrates by the type of lactic acid fermentation with the formation of significant amounts of lactic acid and other organic acids. The acids formed as a result of the vital activity of streptococci inhibit the growth of some putrefactive microorganisms, staphylococci, Escherichia coli, typhoid and dysentery sticks that enter the oral cavity from the external environment.

Staphylococci - Staph are also present in dental plaque and on the gums of healthy people. epidermidis, however, some people may have Staph. aureus.

Rod-shaped lactobacilli in a certain amount constantly live in a healthy oral cavity. Like streptococci, they produce lactic acid, which inhibits the growth of putrefactive and some other microorganisms (staphylococci, E. colli, typhoid and dysentery sticks). The number of lactobacilli in the oral cavity with dental caries increases significantly. To assess the "activity" of the carious process, "lactobacillus test" (determination of the number of lactobacilli) was proposed.

Leptotrichia also belong to the family of lactic acid bacteria and are the causative agents of homofermentative lactic acid fermentation. Leptotrichia are strict anaerobes.

Actinomycetes (or radiant fungi) are almost always present in the oral cavity of a healthy person. Outwardly, they are similar to filamentous fungi: they consist of thin, branching filaments - hyphae, which, intertwining, form the mycelium visible to the eye.

In the oral cavity of healthy people, yeast-like fungi of the genus Candida (C. albicans, C. tropicalis, C. crusei) are found in 40-50% of cases. Pathogenic properties are most pronounced in C. albicans. Yeast-like fungi, multiplying intensively, can cause dysbacteriosis, candidiasis, or local damage to the oral cavity (thrush) in the body. These diseases arise as a result of uncontrolled self-treatment with broad-spectrum antibiotics or strong antiseptics, when antagonists of fungi from representatives of normal microflora are suppressed and the growth of yeast-like fungi resistant to most antibiotics increases (antagonists are some representatives of microflora that suppress the growth of other representatives).

Spirochetes inhabit the oral cavity from the moment the baby teeth erupt in a child and from that time on they become permanent inhabitants of the oral cavity. Spirochetes cause pathological processes in association with fusobacteria and vibrios (ulcerative stomatitis, Vincent's angina). Many spirochetes are found in periodontal pockets during periodontitis, in carious cavities and in the dead pulp.

In half of healthy people, protozoa can live in the mouth, namely Entamoeba gingivalis and Trihomonas. Most of them are found in dental plaque, purulent contents of periodontal pockets with periodontitis, with gingivitis, etc. They multiply intensively with unhygienic maintenance of the oral cavity.

The normal microflora of the oral cavity is quite resistant to the action of antibacterial factors of the oral fluid. At the same time, it itself participates in the protection of our body from microorganisms coming from outside (its normal microflora suppresses the growth and reproduction of pathogenic "aliens"). The antibacterial activity of saliva and the number of microorganisms living in the oral cavity are in a state of dynamic equilibrium. The main function of the antibacterial system of saliva is not to completely suppress the microflora in the oral cavity, but to control its quantitative and qualitative composition.

When isolating microorganisms from different zones of the oral cavity of adults, the predominance of certain species in different areas was noted. If we divide the oral cavity into several biotopes, the following picture will appear. Due to its vastness, the mucous membrane has the most variable composition of microflora: on the surface, gram-negative anaerobic flora and streptococci are predominantly allocated. In the sublingual folds and crypts of the mucous membrane, obligate anaerobes predominate; streptococci and corynebacteria are found on the mucous membrane of the hard and soft palate.

As the second biotope, the gingival groove (groove) and the liquid in it are isolated. There are bacteroids (B. melaninogenicus), porphyromonas (Porphyromonas gingivalis), prevotella intermedia, as well as actinobacillus actinomycetemcomitans (Actinibacillus actinomicitemcomitans), yeast-like fungi and other mycoplasma

mouth lymphoid microorganism periodontium

Diseases parodontaGlavnye bacterial species associated with these zabolevaniyamiOstry ulcerative gingivitBacteroidus intermedius, SpirochetesGingivit beremennyhBacteroidus intermediusParodontit vzroslyhBacteroidus gingivalis, intermedius, Prevotella intermediaLokalizovanny juvenile periodontitis (Best Junior) Actinobacillus actinomicitemcomitans, CapnocytophagaBystro progressive periodontitis (BPP) of adults (35 years old) Actinobacillus actinomicitemcomitans, Bacteroidus intermedius, Fusobacterium nucleatum, Peptostreptococcus micros, Prevotella intermedia, Porphyromonaas gingivalis

As follows from the above facts, caries and inflammatory diseases of the oral cavity occur when the normal balance between its own and foreign microflora is disturbed. Therefore, hygiene products with antibacterial components should be aimed at maintaining the constancy of microflora at the physiological level, i.e. when there is no shift in the quantitative and qualitative composition of microorganisms in favor of pathogenic ones throughout the entire period of life of the organism.

2. Oral cavity-concept, structure features, functions

The oral cavity is the space bounded in front by the lips and teeth, from the side by the surface of the cheeks, behind by the glossopharyngeal rings, below by the tongue and the hyoid space. The oral cavity communicates through the oral opening and nose - with the external environment, through the pharynx and esophagus - with the lungs, ear cavity, stomach and esophagus. Thus, the oral cavity is a formation unique to the human body, which simultaneously borders on the external and internal environment of the body, which can, by physiological and physiologically appropriate movements, limit or completely isolate itself from the external environment, from the environment of the nose, pharynx and the digestive system. That is, this is a formation that simultaneously communicates widely both with the external environment and with the internal environments of the body, while with the help of physiological mechanisms and adaptations, it is able to limit itself both from the external and from the internal environment of the human body.

One of the main features of the oral cavity is its constant connection and communication with the external environment. In this respect, it has an analogy only with the naso-ear-pharyngeal space, the anus. However, these last two cavities are intended for communication with the external environment, either episodically (anus), or in order to gradually adapt the external environment, its main element - air for the conditions of its consumption by the human body - for moisturizing, warming, and purification.

In this regard, the communication of the oral cavity with the external environment has completely different functions, goals and objectives. The main function of communicating the oral cavity with the external environment is to receive and prepare food and liquid for the internal environment, and also partially for the intake of air into the body. The oral cavity is designed for nibbling, moving, softening, chewing, soaking, initial enzymatic digestion and subsequent ingestion of food. Since any food, like the air environment, is an infected environment, it is natural that the oral cavity is an environment in which microflora of various types, composition and quantities are constantly located. The microflora of the oral cavity has several mechanisms of adaptation in the mouth, mechanisms of existence, reproduction and life in the oral cavity. Conventionally, the microflora in the oral cavity can be divided into a number of types.

The main one is various types of sap-rophytes, which have adapted to the conditions of the oral cavity, are in physiological equilibrium, survive in it and do not seem to do any harm to individual tissue formations of the oral cavity.

The second group is microflora, passing through the oral cavity, accidentally getting into it. Sometimes it can be pathogenic. In this case, it can promote infection and invasion and have an adverse effect on the macroorganism or its individual organs and systems and be the cause of their main infection (the so-called oral route of infection). The third group - opportunistic microorganisms that infect the oral cavity, live and multiply in it, finding a niche for infection, reproduction and residence. These are various types of fungi, cocci, bacilli, specific microflora. They are constantly in the oral cavity without causing any negative influences. However, if the body is weakened, a decrease in protective properties is observed, these types of microorganisms can acquire a pathogenic property and cause the development of various pathological processes in the oral cavity.

Finally, there is a fourth group of microorganisms. These are mainly unpretentious microbes that survive well in the oral cavity, for example, Str. mutis. These types of microorganisms, under the influence of sugar consumption, have learned to colonize the oral cavity in the form of dental plaque, soft dental plaque, which have adapted to an autonomous existence in the oral cavity, which is practically not dependent on the macroorganism. They store food for future use, in the form of glycogen-like compounds, which allows them to safely survive the periods between human meals. Dental plaque can be removed only mechanically, which makes the fight against it, using a large arsenal of various means for oral hygiene, a very important and pathogenetically justified method of preventing dental caries and periodontal disease. In the plaque, the microflora lives autonomously, which allows it to exist and multiply regardless of the state of the macroorganism. Therefore, both saprophytic and pathogenic microflora can survive in the supra- and subgingival dental plaque for a long time. At the same time, the effect on the macroorganism, even very active, cannot disrupt the autonomous life of the plaque microorganisms, they can persist there indefinitely and the plaque at the same time performs the function of a kind of microflora depot.

Thus, the microflora of the oral cavity is specific, unlike the flora of other cavities, both in composition, quantity, and function. It is necessary to clearly understand that without microflora in the oral cavity normal functioning of its organs is impossible and any attempts to remove it are not only useless, but harmful, since they can lead to dysacteriosis. Therefore, microbial maintenance of the oral cavity cannot be considered as a pathogenetic method of combating major dental diseases. However, this does not mean that antimicrobial effects on the oral organs are not needed. No, they are necessary in cases when they have a specific pathogenetic purposeful nature.

Other important functions of the oral cavity include providing conditions for chewing food, preparing a food lump, participating in the process of digestion and swallowing food. Such conditions are created in it primarily due to the constant presence of oral fluid in the mouth. Its main sources are the secret of three pairs of large salivary glands - parotid, submandibular and sublingual, which constantly function to provide moisture to both the organs of the oral cavity, teeth, mucous membrane, and food entering it. Due to its high viscosity, viscosity, adsorption, the mixed secret reliably moisturizes the oral cavity and also permeates the food mass. Without such impregnation, it is impossible to moisten and crush food, to lick it and overcome its friction in the mouth. Only by reaching the grinding and soaking process with the help of saliva can food be prepared for swallowing and swallowing.

In addition to the large salivary glands, ducts of a significant number of small salivary glands exit into the oral cavity, which are located in large numbers in the areas of CO, to a lesser extent washed by saliva. Therefore, the role of small salivary glands in moisturizing the mucous membrane is very large. The secretion of all glands is constant, but at different rates, which increases sharply when stimulated, especially in connection with food intake. There is always a residual amount (1-3 ml) of free secretion in the oral cavity, which is the norm. In total, the glandular apparatus, located in the tissues of the mouth, secretes up to 1.5-2 liters of its secret during the day.

At the same time, it is necessary to know that about 25% of all people suffer from decreased secretion of the salivary glands (dry mouth syndrome), which brings serious suffering to such patients. A dry mouth leads to disruption, difficulty and pain in the movement of food in the mouth, to difficulties in the formation of a food lump. Such patients cannot eat without drinking water, they are prone to various inflammatory diseases of the concomitant oral cavity. It is likely that the "dry mouth syndrome" is associated with the epochal process of jaw reduction, a decrease in free anatomical space for the salivary glands, a violation of their reduction, innervation, and blood supply. The establishment and treatment of such a syndrome plays an important role in both the pathogenesis and treatment of diseases of oral mucosa. In the clinic, there are sometimes cases of prolonged and pronounced hypofunction of the glandular apparatus, this condition leads to a disease that is called xerostomia. His clinic, the mechanism of development, several decades ago, was described in detail by the domestic teacher F.A. Zverzhkhovsky (1915).

A third source of fluid in the mouth is fluid sweating from the gingival sulcus (“gum fluid”). It is a liquid very rich in cell forms and enzymes, the volume of which is small. On the one hand, it also plays a certain role in the formation of the composition and volume of saliva, on the other hand it has a significant effect on the state and nature of the protective mechanisms of the marginal periodontium.

In addition to the salivary glands, in some individuals, an accumulation of sebaceous glands is sometimes observed. Their favorite place of localization is the transitional CO of the lips, cheeks, along the line of teeth closing. Their excessive development in the epithelial integuments of the mucous membrane and skin is described under the name seborrhea.

A number of chemical and physical processes play a huge role in the oral cavity. Of the chemical processes, first of all, I would like to mention the digestive function of the oral cavity. It is mainly due to the high activity of salivary amylase, which affects the starch-like constituents of food, breaking them down into dextrose up to maltose. This stage of digestion is very important and should always be considered by dentists and internists. Mixed saliva contains many other digestive enzymes - protease, peptidase, glycosidase, maltase, etc., but they are all of microbial or cellular origin, low concentration and do not play any significant role in digestion (Table 1), but with on the other hand, fluctuations in the content of individual enzymes and their inhibitors are very significant for the development of individual dental diseases.

The saliva contains the hormone parotin, which is produced by the parotid salivary glands and is involved in the regulation of Ca metabolism. It contains in a high concentration the factor of the coagulation and anti-coagulation systems of the blood, a number of factors affecting the regeneration processes, the metabolic processes of the liver, the function of the stomach, etc.

Saliva contains a number of factors (most of which have biologically active properties) - lysozyme, immunoglobulins, etc., capable of destroying microflora, binding toxins, and carrying out antimicrobial and immunological defense mechanisms.

The most important function of saliva is mineralizing. It is carried out due to the presence of calcium and phosphorus ions in it in a supersaturated state (2 times higher than in the blood). Due to the state of oversaturation, the teeth cannot dissolve in saliva, and the latter cements cracks and defects in the enamel of the teeth, contributing to their intact state.

In the last 10 years, a hypothesis has been put forward about the micellar colloidal structure of saliva (V.K. Leont'sv et al.). Its essence is that saliva (Scheme 1.2) is not an ordinary solution, but a colloidal system consisting of micelles spontaneously formed on the basis of calcium and phosphate. All free liquid is bound to these micelles, which is why saliva is so viscous and able to retain its shape. Any impact on saliva in this case is nothing more than an effect on the stability of micelles, which they can lose, thereby disrupting the properties of saliva. This new hypothesis of the structure of saliva allows modern, new understanding of the mechanism of functioning of saliva, the influence on the properties of changes in its composition.

The most important function of the oral cavity is the processes of adsorption and desorption occurring in it. All substances that enter the oral cavity - food, microflora, drugs, liquids - have the ability to be sorbed on its organs. Especially the SB of the language has such a high ability. Sugar from food, for example, can be kept on it for up to 60 minutes. Soft dental plaque and gingival grooves also have a high capacity for adsorption. It is in them that food residues, food and microbial detritus, possessing high enzymatic activity, accumulate, which is not indifferent for the state of the OSS. Desorption of these substances is easily accomplished by a number of weak solutions of acids, especially citric acid. She herself very strongly binds to the structures described above, displacing food, detritus, microflora.

In the oral cavity there are highly metabolite areas that are very well washed with saliva, well cleaned. These are the chewing surfaces of the teeth, a number of areas of the gums, the mucous membrane of the cheeks, the back of the lips. At the same time, there are areas that are very difficult to clean in a natural way - these are the gingival grooves, fissures of the teeth, their contact surfaces, the X-ray areas, some areas of the floor of the oral cavity. Finally, in the oral cavity, in addition to soft dental plaque, there are also a number of acquired structures, genetically indeterminate, that arise during a person's life - this is a highly entabolic saliva sediment, tartar, dental pellicle, fillings, crowns, and prostheses. All of them are not indifferent to the life of the oral cavity and the performance of its functions.

One of the most important functions of the oral cavity is its self-cleaning. Physiologically, it is formed in such a way and its anatomy is such that the oral cavity is easily cleared of food debris, detritus, etc. This occurs due to several processes - the process of swallowing food, constant washing with saliva, movement of the tongue, cheeks, jaws, floor of the mouth. Any violation of the process of self-cleaning of the oral cavity is not indifferent to its well-being, health and functioning. Violation of self-cleaning can occur with the "dry mouth syndrome", the formation of deep periodontal pockets, a number of dentoalveolar anomalies, the presence of carious teeth, with poorly placed fillings and prostheses, chewing laziness. In these cases, the role of rational oral hygiene, including continuous, multiple and professional, is especially important. The process of self-cleaning should always be paid attention to in case of diseases of the oral mucosa. There are also a number of features inherent in the oral cavity - a high degree of resistance and adapted to a large number of physical and chemical factors. Among them, it should be noted the effect of various chemicals (acids, alkalis, certain chemicals), high and low temperatures, changes and fluctuations in atmospheric pressure, the effects of dryness and microbial invasion. Sugar and its products play a special role in the physiology and pathology of the oral cavity. The main feature is the ability of sugar (the only product) to completely metabolize in the mouth. For this, it has all the conditions - humidity, good adsorption, ideal temperature. The sugar in the mouth enters into the glycolysis process, as a result of which it is quickly converted into lactic acid. This process in the oral cavity takes 3-5 minutes. When sugar is taken in the mouth, a kind of "metabolic explosion" occurs (Scheme 3). The amount of lactic acid within a few minutes increases 10-15 times and only after 1 hour returns to normal. This "metabolic explosion" is nothing more than the rapid glycolysis of sugar into lactic acid. The latter affects the teeth (acid attack), which can gradually lead to tooth decay. Thus, sugar intake is, as it were, a resolving factor in acid carious attack. Therefore, the cariogenic role of sugar is the main sweet substance. Sugar is not a natural food for the mouth. It has only been used in large quantities for the last hundred years. During this time, the oral cavity with its organs failed to adapt to self-cleaning from it, as a result of which, as a massive dental disease, caries and gum disease appeared - those in the pathogenesis of which sugar and the soft plaque arising from it play an essential pathogenetic role. Thus, the oral cavity is a very peculiar anatomical formation, completely unlike other cavities of the human body; with diverse and sharply differing functions, features of composition and structure; numerous functions: digestion, protective, self-purification, mineralizing, etc. OSS is an indicator of the state of the human body and its relationship with the external environment. The ability to "read" and see the clinical state of the mucosa, to catch the deviations that arise in it, plays an essential role both for assessing its immediate state and for identifying early signs of changes associated with both endogenous and exogenous effects. Without knowing them, and not taking them into account, it is impossible to successfully treat and prevent OCD diseases.

Conclusion

mouth iron secretion salivary

The microflora of the oral cavity is extremely diverse and includes bacteria, actinomycetes, fungi, protozoa, spirochetes, ricketsia, viruses. It should be noted that a significant part of the microorganisms in the oral cavity of adults are anaerobic species.

The largest group of bacteria constantly living in the oral cavity is represented by cocci - 85-90% of all species. They have significant biochemical activity, decompose carbohydrates, break down proteins to form hydrogen sulfide.

Literature

1. Microbiology. / Ed. A.A. Vorobyov. - M .: Medicine, 1998 and other years of publication.

2. Microbiology and immunology. / Ed. A.A. Vorobyov. - M .: Medicine, 1999 and other years of publication.

3. Guide to practical training in medical microbiology, virology and immunology. Ed. V.V. Teza. - M .: "Medicine", 2002.

4. Guide to practical training in medical microbiology. - Tomsk, 2003 and other editions for practical training (Ed. Tez, Borisov, etc.).

5. Textbook: Medical Microbiology. / Ed. IN AND. Pokrovsky, O.K. Pozdeeva. - M .: GEOTAR Medicine, 1999 and other years of publication.

6. Akatov A.K., Zueva. B.C. Staphylococci - M .: Medicine, 1983.

7. Actual problems of clinical microbiology (collection of scientific papers) NIIEM them. N.F. Gamalei. - M., 1989.

8. Antonov V.B., Yarobkova N.D., Chaika N.A. Aspergillosis and AIDS. - SPb., 1992.

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E.G. Zelenova,

M.I., Zaslavskaya E.V. Salina,

SP. Rassanov

Publishing house of NGMA

NIZHNY NOVGOROD

MINISTRY OF HEALTH OF THE RUSSIAN FEDERATION

NIZHNY NOROD STATE MEDICAL ACADEMY

E.G. Zelenova, M.I. Zaslavskaya, E.V. Salina, SP. Rassanov

ORAL MICROFLORA: NORM AND PATHOLOGY

Lectures for students of the Faculty of Dentistry

Tutorial

Scientific editor prof. A.N. MAYANSKY

Publishing house NGMA NIZHNY NOVGOROD

UDC 616-093 / -098 (075.8)

Zelenova E.G., Zaslavskaya M.I., Salina E.V., Rassanov SP. Oral microflora: norm and pathology: textbook. Nizhny Novgorod: Publishing house of the NGMA,

The textbook is an expanded version of the lecture course on oral microbiology and is compiled in accordance with the program in microbiology, virology, immunology and the course of oral microbiology for students of dental faculties of higher medical educational institutions (2001), the curriculum in oral microbiology ( 2000), as well as taking into account the provisions on viutrivuz certification of practical and theoretical training of students.

The manual can be used for independent work of students, control of theoretical knowledge at the final seminars and conducting an exam in the section "Microbiology of the oral cavity".

Scientific editor prof. A.N. MAYANSKY

ISBN 5-7032-0525-5

FOREWORD

In recent years, there has been an increase in dentists' interest in fundamental disciplines, including medical microbiology and immunology. Of all the branches of microbiology for the special training of a dentist, the section that studies the normal, or resident, human flora, in particular the indigenous microflora of the oral cavity, is of paramount importance. Caries and periodontal diseases, which occupy one of the leading places in human pathology, are associated with the permanent microflora of the oral cavity. There is ample evidence that the prevalence of them in the population in many countries reaches 95-98%.

For this reason, knowledge of the issues of the ecology of the oral cavity, the mechanisms of the formation of normal microbial flora, the factors regulating the homeostasis of the oral ecosystem, is absolutely essential for students of dental faculties. In the textbook "Microflora of the oral cavity: norm and pathology", modern data on the importance of normal flora and the mechanisms of local immunity of the oral cavity in the occurrence of pathology of the oral cavity are presented in an accessible form.

This manual has been prepared in accordance with the curriculum on the topic "Microbiology of the oral cavity" and supplements the section "Microbiology and immunology of dental diseases" of the textbook LB Borisov "Medical microbiology, virology, immunology", M., Medicine, 2002.

Head Department of Therapeutic Dentistry

NSMA, MD, DSc, Professor

L.M. LUKIN

NORMAL ORAL MICROFLORA

1. Normal microflora of the oral cavity. Role in pathology. 2. Autochthonous and allochthonous species. Permanent (indigenous) and optional flora. 3. Factors affecting the formation of the microflora of the oral cavity. 4. Mechanisms for the formation of normal flora. Adhesion and colonization. Coagregation. 5. Coccal flora of the oral cavity. 6. Rod-shaped forms of bacteria that live in the oral cavity. 7. Unstable microflora of the oral cavity.

1. Normal microflora of the oral cavity. Role in pathology.The human oral cavity is a unique ecological system for a wide variety of microorganisms that form a permanent (autochthonous, indigenous) microflora, which plays an important role in human health and diseases. In the oral cavity, persistent microorganisms are often associated with two main diseases - caries and periodontal disease.Apparently these diseases arise after an imbalance among resident species in a given microbiocenosis under the influence of certain factors. To imagine the process that entails caries or periodontal disease, and the contribution of microorganisms to the development of these diseases, it is necessary to know the ecology of the oral cavity, the mechanisms of formation of normal microbial flora, and the factors that regulate the homeostasis of the oral ecosystem.

2. Autochthonous and allochthonous species. Constant (indigenous) and

optional flora.Among the microbes of the oral cavity, there are autochthonous - species specific for a given biotope, allochthonous - immigrants from other biotopes of the host (nasopharynx, sometimes intestines), as well as species - immigrants from the environment (the so-called alien microflora).

Autochthonous microflora is divided into obligate, which constantly lives in the oral cavity, and facultative, in which opportunistic bacteria are more often found.

The main importance is the autochthonous microflora of the oral cavity, among which obligate species prevail; facultative types are less common, they are most typical for certain diseases of the teeth, periodontal, oral mucosa and lips.

The composition of the normal microflora of the oral cavity includes bacteria, viruses, fungi and protozoa. The most numerous are bacterial biocenoses,which play a major role in maintaining the constancy of a given biotope.

Microorganisms enter the oral cavity through food, water and air. The richness of food resources, constant humidity, optimal pH and temperature values \u200b\u200bcreate favorable conditions for adhesion and colonization of various microbial species.

3. Factors affecting the formation of the microflora of the oral cavity. The species composition of the microbial flora of the oral cavity is normally fairly constant. However, the number of microbes can fluctuate significantly. The following factors can influence the formation of the microflora of the oral cavity:

1) the condition of the oral mucosa, structural features (folds of the mucosa, gingival pockets, desquamated epithelium);

2) temperature, pH, oxidation-reduction potential (ORP) of the oral cavity;

3) the secretion of saliva and its composition;

4) the condition of the teeth;

5) food composition;

6) hygienic condition of the oral cavity;

7) normal functions of salivation, chewing and swallowing;

8) natural resistance of the body.

Each of these factors in different biotopes of the oral cavity influences the selection of microorganisms and helps to maintain a balance between bacterial populations.

Disorder of salivation, chewing and swallowing always leads to an increase in the number of microorganisms in the oral cavity. Various anomalies and defects that make it difficult to flush out microbes with a current of saliva (carious lesions, pathological gingival pockets, poorly fitted fixed dentures, various types of metal crowns) also provoke an increase in the number of microorganisms.

There are more microbes in the oral cavity in the morning on an empty stomach and least of all immediately after a meal. Solid food is more likely to reduce germs.

4. Mechanisms for the formation of normal flora. Adhesion and colonization.

Coagregation. To settle in the oral cavity, microorganisms must first attach to the mucosal surface or to the teeth. Adhesion (adhesion) is necessary to ensure resistance to saliva flow and subsequent colonization (reproduction).

It is known that nonspecific (primarily hydrophobic) interactions and specific (ligand - receptor) contacts play a role in the adhesion of microorganisms to the buccal epithelium. In this case, mainly protein components have adhesive properties. In particular, pili or fimbriae can participate in the adhesion process on the part of gram-negative bacteria, while in gram-positive bacteria, lipoteichoic acids can act as adhesins. In addition, glycosyltransferases and glycosylated proteins (lectures) are involved in adhesion. On the other hand, specific receptors of the epithelial cells of the oral cavity are involved in the adhesion process (specific interactions also exist during adhesion to the tooth surface).

Some bacteria do not have their own adhesins, then they are fixed on the surface of mucous membranes, using the adhesins of other microorganisms, i.e. there is a process of coaggregation between the bacterial species of the oral cavity. Coagregation can contribute to the development of dental plaque.

The normal microflora of the body begins to form at the birth of a child. In the oral cavity of a newborn, it is represented by lactobacilli, non-hemolytic streptococci and non-pathogenic staphylococci. Within 6-7 days, these microorganisms are replaced by microbes characteristic of an adult.

In the oral cavity there can be up to 100 types of microorganisms, according to other sources - up to 300 (see table). Its main inhabitants in an adult are bacteria of a predominantly anaerobic type of respiration (3/4 of all microbial species), the rest of the species are represented by facultative anaerobes. In the oral cavity, the largest group of bacteria is cocci.

The microbial flora of the oral cavity is normal

Microorganisms				Detection rate in
				periodontal pockets,%
		Detection frequency	amount
		arms,%

Resident flora
1. Aerobes and faculty
tative anaerobes:

			1.5x105


			106 -108

	Saprophytic		105 -107
neisseria

	Lactobacillus		103 -104
	Staphylococci		103 -104
	Diphtheroids
			is defined
	Hemophilia
			is defined
	Pneumococci			Undefined
			is defined
10. Other cocci			102 -104

mycobacteria			is defined
12. Tetracocci
			is defined
13. Yeast-like			102 - 103

14. Mycoplasma			102 - 103	11e determined
	Obligate
anaerobes:
	Veillonella		106 - 108

	Anaerobic
streptococci		is defined
(peptostreptococci)
	Bacteroids
		is defined
	Fusobacteria	102 -103
	Filamentous bacteria	102 -104

	Actinomycetes and
anaerobic diphtheroids		is defined

	Spirilla and vibrio
		is defined
	Spirochetes
(saprophytic borrelia,		is defined
treponema and
leptospira)
	The simplest:
	Entamoeba gingivalis
	Trichomonas elongate

Unstable flora

optional
anaerobes:
Gram-negative

		10-102
		10-102
		10-102

		is defined

		is defined

		is defined

		is defined
	Obligate
anaerobes:
Clostridia:
	Clostridium putridium
		is defined
	Clostridium perfringens
		is defined

Note: + + found frequently; + not very often; ± rarely, 0 not detected.

5. Coccal flora of the oral cavity.

Genus Staphylococcus. Staphylococci in the oral cavity of a healthy person are found on average in 30% of cases, gram-positive, when microscopic they are located in the form of bunches of grapes. Optional anaerobes. Staphylococci, like all representatives of the microbial landscape of the oral cavity, are chemoorganotrophs.

Staphylococcus epidermidis is mainly present in dental plaque and on the gums of healthy people. In some people, Staphylococcus aureus can be found in the mouth. Possibly a healthy carrier of staphylococci on the nasal and pharyngeal mucosa.

Possessing significant enzymatic activity, staphylococci take part in the breakdown of food debris in the oral cavity. Pathogenic staphylococci (coagulase-positive), found on the mucous membrane of the nasopharynx and in the oral cavity, are a common cause of endogenous infections, causing various purulent-inflammatory processes in the oral cavity.

Genus Streptococcus. Streptococci are the main inhabitants of the oral cavity (in 1 ml of saliva - up to 108 - 10 "streptococci). In stained smears, streptococci are arranged in chains, gram-positive. Most of them are facultative anaerobes or microaerophiles, but there are also strict anaerobes (for example, peptostreptococci) Chemoorganotrophs They grow poorly on simple nutrient media under aerobic conditions, special nutrient media (blood agar, sugar broth) are needed for growth. In the external environment, they are less stable than staphylococci. With significant enzymatic activity, streptococci ferment carbohydrates with the formation of lactic acid, causing lactic acid fermentation Acids resulting from fermentation inhibit the growth of a number of putrefactive microbes found in the oral cavity.

Streptococci, vegetating in the oral cavity, constitute a special ecological group and are called "oral". These include the following species: S.mutans, S.salivarius, S.sanguis, S.mitis, S.oralis, etc. Oral streptococci differ from each other in their ability to ferment carbohydrates and form hydrogen peroxide. On blood agar, they form punctate colonies surrounded by a greenish zone of α-hemolysis. Colonization by oral streptococci of various parts of the oral cavity has qualitative and quantitative variations depending on living conditions. S.salivarius and S.mitis are present in 100% of cases in the oral cavity. S.mutans and S.sanguis are found in large numbers on the teeth, and S.salivarius mainly on the tongue. S.mutans and S.sanguis were detected in the oral cavity only after tooth damage.

The next group of gram-positive cocci found in the oral cavity are peptococci. They are arranged singly, in pairs, in the form of short chains. Strict anaerobes, chemoorganotrophs with complex nutritional needs. They are demanding on nutrient media, grow better in the presence of fatty acids. Most often, peptococci are found in associations with fusobacteria and spirochetes with deep pulpitis, periodontitis, and maxillofacial abscesses.

Genus Veillonella. Veillonella are small gram-negative cocci located

heaps (disordered clusters), pairs or short chains. Strict anaerobes. Chemoorganotrophs with complex nutritional needs. They grow poorly on nutrient media, but their growth is noticeably improved with the addition of lactate, which is a source of energy for them. They well decompose low-molecular metabolic products of carbohydrates - lactate, pyruvate, acetate - to CO2 and H2, promoting an increase in the pH of the medium, as a result of which the growth of other microorganisms is suppressed. The concentration of Veillonella in saliva is approximately the same as that of green streptococci. In the oral cavity of healthy people, they are constantly present in large quantities (in 1 ml of saliva up to 107 - 10 ").

It is believed that due to the catabolism of lactic acid formed by green streptococci, Veillonella may have an anti-carious effect. They usually do not independently cause the development of pathological processes, but they can be part of mixed groups of pathogens. Their number increases with inflammatory processes, with odontogenic abscesses of the oral cavity.

Genus Neisseria. Neisseria are gram-negative diplococci. Strict aerobes. Neisseria is always found in large quantities in the oral cavity of healthy people (up to 1-3 million in 1 ml of saliva). There are pigment-forming species and non-pigment-forming species. The latter are most often found in the pulp and periodontium in acute serous inflammation and in catarrhal inflammation of the oral mucosa.

In addition to cocci, the oral cavity contains a variety of rod-shaped forms of bacteria.

6. Rod-shaped forms of bacteria that live in the oral cavity.

Genus Lactobacillus. Lactobacilli are lactic acid bacteria, gram-positive, immobile, do not form spores and capsules, are distinguished by high polymorphism - short and long, thin and thick, filamentous and branching forms. Optional anaerobes. They cause acidic fermentation with the formation of a large amount of lactic acid. According to their saccharolytic properties, they differ from each other and on the basis of this, homofermentative and heterofermentative species are distinguished. Homofermentative species (Lactobacillus casei) cause homofermentative fermentation and form only lactic acid during the decomposition of carbohydrates. Heterofermentative species (Lactobacillus fermenti, Lactobacillus brevis)

cause heteroenzymatic lactic acid fermentation, form lactic acid (50%), acetic acid, alcohol, carbon dioxide (50%).

Due to the formation of a large amount of lactic acid during the life of lactobacilli, they retard the growth (are antagonists) of other microbes: staphylococci, Escherichia coli and dysentery bacilli. The antagonistic properties of lactobacilli in relation to a number of putrefactive microbes were noticed by II Mechnikov.

Lactobacilli are non-pathogenic microorganisms and therefore do not cause disease. The number of lactobacilli in the oral cavity with caries increases and depends on the size of carious lesions.

Genus Corynebacterium. Corinebacteria are almost always and in large quantities found in the oral cavity of a healthy person. These are non-pathogenic members of the genus.

Lecture 1

NORM AND PATHOLOGY

Unstable microflora of the oral cavity.

Representatives of the unstable microflora of the oral cavity are found in insignificant quantities, rather rarely and not in all subjects. Their long-term stay in the oral cavity, apparently, is prevented by nonspecific factors of protection of the oral cavity. In addition, lactobacilli and streptococci, which are constantly present in the oral cavity, are antagonists of many non-permanent inhabitants of the oral cavity (sarcina, Escherichia coli, Proteus, etc.) and contribute to the release of the oral cavity from them.

In case of violations of the physiological state of the oral cavity, representatives of the unstable flora can linger in it, multiply and cause pathological processes. A certain role in this is played by bacteria included in the microbiocenosis of the human intestine. Normally, the microflora of the oral cavity should not contain representatives of enterobacteria. In some pathological processes, representatives of four generic taxa of the intestinal family can be distinguished:

1) Escherichia; 2) Aerobacter; 3) Proteus; 4) Klebsiella.

With purulent-inflammatory processes, representatives of the genus are sometimes found

A certain role is played by yeast-like fungi of the genus Candida, which are either absent in normal flora in healthy people or are found in very small quantities.

The unstable microflora of the oral cavity also includes bacteria belonging to the genus Clostridium. These are gram-positive spore-forming rods, obligate anaerobes. It is extremely rare in the oral cavity of healthy people. They can be found only in carious cavities, in root canals. At the same time, the greatest role in the pathology of the oral cavity is played by Clostridium perfringens, a microbe with an extremely high saccharolytic and proteolytic activity; its metabolism contributes to the breakdown of collagen, the destruction of dentin with caries.

1. Normal microflora of the oral cavity. Role in pathology.The human oral cavity is a unique ecological system for a wide variety of microorganisms that form a permanent (autochthonous, indigenous) microflora, which plays an important role in human health and diseases. In the oral cavity, persistent microorganisms are often associated with two main diseases - caries and periodontal disease. Apparently, these diseases arise after an imbalance among resident species in a given microbiocenosis under the influence of certain factors. To imagine the process that entails caries or periodontal disease, and the contribution of microorganisms to the development of these diseases, it is necessary to know the ecology of the oral cavity, the mechanisms of formation of normal microbial flora, and the factors that regulate the homeostasis of the oral ecosystem.

2. Autochthonous and allochthonous species. Permanent (indigenous) and optional flora.Among the microbes of the oral cavity there are autochthonous- species specific for a given biotope, allochthonous- immigrants from other biotopes of the host (nasopharynx, sometimes intestines), as well as species - immigrants from the environment (the so-called alien microflora).

Autochthonous microflora is divided into obligate, which constantly lives in the oral cavity, and facultative, in which opportunistic bacteria are more often found.

The composition of the normal microflora of the oral cavity includes bacteria, viruses, fungi and protozoa. The most numerous are bacterial biocenoses,which play a major role in maintaining the constancy of a given biotope.

3. Factors affecting the formation of the microflora of the oral cavity.The species composition of the microbial flora of the oral cavity is normally fairly constant. However, the number of microbes can fluctuate significantly. The following factors can influence the formation of the microflora of the oral cavity:

1) the condition of the oral mucosa, structural features (folds of the mucosa, gingival pockets, desquamated epithelium);

2) temperature, pH, oxidation-reduction potential (ORP) of the oral cavity;

3) the secretion of saliva and its composition;

4) the condition of the teeth;

5) food composition;

6) hygienic condition of the oral cavity;

7) normal functions of salivation, chewing and swallowing;

8) the natural resistance of the body.

Each of these factors in different biotopes of the oral cavity influences the selection of microorganisms and helps to maintain a balance between bacterial populations.

There are more microbes in the oral cavity in the morning on an empty stomach and least of all immediately after a meal. Solid food is more likely to reduce germs.

4. Mechanisms for the formation of normal flora. Adhesion and colonization. Coagregation.To settle in the oral cavity, microorganisms must first attach to the mucosal surface or to the teeth. Adhesion (adhesion) is necessary to ensure resistance to saliva flow and subsequent colonization (reproduction).