SUBKINGDOM INDOOR BACTERIA -
BACTERIA OR BACTERIOBIONTA

Real bacteria are very ancient organisms, apparently appearing over 3 billion years ago. Like other prokaryotes, they are microscopically small, but their clusters (colonies) are often visible to the naked eye. According to the shape and features of cell association, several morphological groups of real bacteria are distinguished: spherical cocci; diplococci, consisting of pairwise contiguous cocci; streptococci formed by cocci brought together in the form of a chain; sarcins - cocci that look like dense packs; staphylococci - clusters of cocci in the form of a bunch of grapes; bacilli, or rods, are elongated bacteria; arched vibrios; spirilla-bacteria of an elongated, corkscrew-shaped convoluted shape, etc. (Fig. 3). Bacteria have different kinds of flagella and villi

Rice. 3. A variety of forms of bacteria: 1 - rod-shaped, 2 - fusiform, 3 - cocci, 4 - diplococci, 5 - streptococci, 6 - staphylococci, 7 - sarcins, 8 - vibrios, 9 - spirillum, 10 - stalk, 11 - toroids, 12 - star-shaped, 13 - hexagonal, 14 - "multicellular" bacterium

(fimbria) with which they move. Some bacteria move by secreting mucus. Bacteria move quickly, in one second they can cover a distance approximately equal to 20 diameters of their cells.

The flagella of bacteria resemble the flagella of eukaryotes (undulipodia) only externally. Each bacterial flagellum consists of a single flagellin protein molecule that emerges from a "clutch" in the cell wall and is associated with a complex spinning mechanism. Bacterial flagella make rotational movements unlike undulipodia, whose movements are undulating. The direction of movement of bacteria is determined to a large extent by an increase in the concentration of food or oxygen (for aerobes). On the other hand, there are a number of "repellent" substances (repellants) that "repel" bacteria. Using the method of staining with aniline dyes, first proposed in 1884 by K. Gramm, all real bacteria can be divided into two classes (or departments) - gram-positive and gram-negative bacteria (i.e., capable or incapable of staining) with various features structure and chemistry cell wall. Gram stain, in addition to the purposes of classification, is used to identify bacteria, which is especially important when determining pathogenic microorganisms.

The cell wall of many bacteria is surrounded on top by a layer of polysaccharide mucus that forms a capsule. In the cytoplasm of bacteria, inclusions of reserve nutrients are sometimes noticeable. It can be starch or glycogen, but more often volutin is a substance that includes phosphoric acid residues. Bacteria are able to form thick-walled endospores. Genetic recombination in bacteria occurs as a result of the transfer of a portion of a DNA molecule from one bacterial cell to another. Almost all bacteria, along with large circular DNA molecules, have small circular DNA - plasmids. Plasmid exchange is easily accomplished during conjugation bacterial cells, which also contributes to the transmission from one strain to another of some hereditary traits. Mutations are even more important source bacterial variability than genetic recombination.

The main mode of reproduction of bacteria is asexual. The cell at the same time increases in size and divides in two.

during photosynthesis in the Calvin cycle. Chemosynthetic bacteria play an extremely important role in the circulation (biogeochemical cycles) chemical elements in the biosphere. Many of the most important reactions of the circulation of substances, such as nitrification, denitrification, nitrogen fixation, are carried out only by prokaryotes.

Bacteria play the main role in the processes of destruction (destruction), i.e., they are destructors. Some bacteria contain in their cells a special pigment related to chlorophyll called bacteriochlorophyll. They are capable of photosynthesis without the release of oxygen (anaerobic type of photosynthesis), since they lack photosystem II, in which they differ sharply from oxyphotobacteria. To assimilate CO 2, photosynthetic bacteria use hydrogen sulfide, sulfur, thiosulfate, etc. as electron donors.

In relation to oxygen, bacteria are divided into aerobes (existing only in an oxygen environment) and anaerobes (existing in an oxygen-free environment), bacteria are also known that live in both oxygen and anoxic environments (facultative anaerobes).

Bacteria have adapted to a variety of habitat conditions and are cosmopolitan organisms: the same species can be found almost everywhere. In 1 g of soil of agricultural land can contain up to 2.5 billion bacterial cells.

The role of bacteria in human life is enormous. Thus, the production of many food and technical products is impossible without the participation of various fermentative bacteria. The waste products of bacteria are a variety of dairy products: butter, kefir, cheese, koumiss, as well as enzymes, alcohol, citric acid. The processes of fermentation of food products are also associated with bacterial activity. With the help of biotechnology, antibiotics are obtained, which are formed by bacteria in the course of their vital activity. Bacteria are also used in genetic engineering. Enrichment of soils with nitrogen compounds and the creation of bacterial fertilizers are impossible without the participation of nitrogen-fixing bacteria, mainly from the combined genus Rhizobium ( Rhizobiutn), which form nodules on the roots of leguminous plants. Polysaccharides, which form the mucous capsule of bacteria, find a variety of applications.

The negative role of bacteria is also great. Different kinds bacteria cause food spoilage. The most dangerous pathogenic bacteria are the source of various infectious diseases in humans and animals. Bacteria and plants are affected (Fig. 4), although relatively less often, apparently due to the acidic reaction of the environment of plant tissues.

Among gram-positive bacteria, we mention lactic acid fermentation bacteria, tetanus bacilli, and tuberculosis.

wand. Gram-positive organisms also include actinomycetes - prokaryotes that form a multicellular branched mycelium. Mycoplasmas are sometimes placed in the same class - prokaryotes devoid of a cell wall. Gram-negative bacteria include nitrogen-fixing and nitrifying bacteria. In addition to gram-positive and gram-negative bacteria, there are also mycoplasmas - the smallest organisms (about 0.1 microns in diameter), devoid of a shell. They are considered bacteria that have simplified their structure in the process of evolution. Among the photosynthetic bacteria, green and purple sulfur bacteria should be noted. Chemoautotrophic microorganisms are partly true bacteria, partly archaebacteria.

Bacteria are present everywhere, their number is huge, the species are different. anaerobic bacteria- the same types of microorganisms. They can develop and live independently, whether there is oxygen in their feeding environments or it does not exist at all.

energy anaerobic bacteria obtained by substrate phosphorylation. There are facultative aerobes, obligate or other varieties of anaerobic bacteria.

Facultative species of bacteria are almost everywhere. The reason for their existence is the change of one metabolic pathway to a completely different one. This species includes E. coli, staphylococci, shigella, and others. These are dangerous anaerobic bacteria.

If there is no free oxygen, then obligate bacteria die.

Arranged by class:

1. Clostridia- obligate types of aerobic bacteria, can form spores. These are the causative agents of botulism or tetanus.
2. non-clostridial anaerobic bacteria. Varieties from the microflora of living organisms. They play a significant role in the formation of various purulent and inflammatory diseases. Non-spore-forming types of bacteria live in the oral cavity, in the gastrointestinal tract. On the skin, in the genitals of women.
3. Capneistic anaerobes. They live with an exaggerated accumulation of carbon dioxide.
4. Aerotolerant bacteria. In the presence of molecular oxygen, this type of microorganisms has no respiration. But he doesn't die either.
5. Moderately strict types of anaerobes. In an environment with oxygen, they do not die, do not multiply. Bacteria of this species require a nutritional environment with reduced pressure to live.

Anaerobes - bacteroids

Considered the most important aerobic bacteria. They make up 50% of all inflammatory and purulent types. Their causative agents are anaerobic bacteria or bacteroids. These are gram-negative obligate types of bacteria.

Rods with bipolar staining and sizes from 0.5 to 1.5, in areas of approximately 15 microns. They can produce the production of enzymes, toxins, cause virulence. dependent on antibiotic resistance. They can be persistent or just sensitive. All anaerobic microorganisms are very resistant.

Energy generation for gram negative obligate anaerobes carried out in human tissues. Some of the tissues of organisms have an increased resistance to a reduced oxygen value in the food environment.

Under the conditions of the standard, the synthesis of adenosine triphosphate is performed only aerobically. This occurs with increased physical effort, inflammation, where anaerobes act.

ATP is adenosine triphosphate or acid, which appears during the formation of energy in the body. There are several variations of the synthesis of this substance. One of them is aerobic, or there are three variations of anaerobes.

Anaerobic mechanisms for the synthesis of adenosine triphosphate:

• rephosphorylation, which is carried out between adenosine triphosphate and creatine phosphate;
• the formation of transphosphorylation of adenosine triphosphate molecules;
• anaerobic breakdown of blood components of glucose, glycogen.

Formation of anaerobes

The purpose of microbiologists is the cultivation of anaerobic bacteria. To do this requires a specialized microflora, and the concentration of metabolites. It is usually used in research of a different nature.

There are special methods for growing anaerobes. Occur when replacing air with a mixture of gases. There is an action in thermostats with sealing. This is how anaerobes grow. Another method is the cultivation of microorganisms with the addition of reducing agents.

Sphere of nutrition

There is a sphere of nutrition with a general view or differential diagnostic. The base - for the type of Wilson-Blair is agar-agar, which has some content of glucose, 2-x iron chloride, sodium sulfite among its components. Among them there are colonies that are called black.

The Ressel sphere is used in the study of the biochemical qualities of bacteria called Salmonella or Shigella. This medium may contain both glucose and agar-agar.

Ploskirev's environment is such that it can inhibit the growth of certain microorganisms. They make up a multitude. For this reason, it is used for the possibility of differential diagnostic. Here, dysentery pathogens, typhoid fever, and other pathogenic anaerobes can be successfully produced.

The main direction of the bismuth-sulfite agar medium is the isolation of Salmonella by this method. This is done with the ability of Salmonella to produce hydrogen sulfide.

In the body of every living individual, many anaerobes live. They cause various types of infectious diseases in them. Infection with an infection can occur only with a weakened immune system or disruption of the microflora. There is a possibility of infection getting into a living organism from the environment. It could be in autumn, in winter. Such hit of infections is saved during the listed periods. The ailment caused sometimes gives complications.

Infections caused by microorganisms - anaerobic bacteria, are directly linked to the flora of the mucous membranes of living individuals. With living places anaerobes. Each infection has several pathogens. Their number usually reaches ten. An absolutely specified number of diseases that cause anaerobe cannot be determined with accuracy.

Due to the difficult selection of materials intended for the study of the transportation of samples, the determination of bacteria. Therefore, this type of component is often found only with already chronic inflammation in humans. This is an example of a careless attitude to one's health.

Anaerobic infections are periodically exposed to absolutely all people with different ages. In small children, the degree of infectious inflammation is much greater than in people of other ages. Anaerobes often cause diseases inside the skull in humans. Abscesses, meningitis, other types of diseases. The spread of anaerobes is carried out with blood flow.

If a person has a chronic disease, then anaerobes can form anomalies in the neck or head. For example: abscesses, otitis or lymphadenitis. Bacteria are dangerous for the gastrointestinal tract, lungs of patients.

If a woman has diseases of the genitourinary system, then there is a risk of anaerobic infections. Various diseases of the skin, joints - this is also a consequence of the life of anaerobes. This method is one of the first to indicate the presence of an infection.

Reasons for the appearance of infectious diseases

Human infections are caused by those processes in which energetic anaerobe bacteria enter the body. The development of the disease may be accompanied by unstable blood supply, the appearance of tissue necrosis. These can be injuries of a different nature, swelling, tumors, vascular disorders. The appearance of infections in the oral cavity, diseases in the lungs, inflammation of the pelvic organs, other diseases.

Infection can develop in a peculiar way for each species. The development is influenced by the type of pathogen, the health of the patient. It is difficult to diagnose such infections. The seriousness of diagnosticians is often based on assumptions alone. There is a difference in the characteristics of infections that arise from non-clostridial anaerobes.

The first signs of infection are gas formation, any suppuration, the appearance of thrombophlebitis. Sometimes tumors or neoplasms can be signs as signs. They can be neoplasms of the gastrointestinal tract, uterine. Accompanied by the formation of anaerobes. At this time, an unpleasant odor may come from a person. But, even if the smell does not exist, this does not mean that there are no anaerobes as pathogens for infection in this organism.

Features for getting samples

The first examination in anaerobic infections is an external examination. general view man, his skin. Because the presence of skin diseases in humans is a complication. They indicate that the vital activity of bacteria is the presence of gases in infected tissues.

In laboratory studies, determining a refined diagnosis, it is necessary to correctly obtain a sample of infected matter. Often specialized equipment is used. The best method of obtaining samples is considered to be aspiration performed with a straight needle.

Types of samples that do not correspond to the possibility of continuing analyzes:

• sputum acquired by self-excretion;
• bronchoscopy samples;
• types of smears from the vaults of the vagina;
• urine from free urination;
• types of faeces.

Samples are subject to research:

1. blood;
2. pleural fluid;
3. transtracheal aspirates;
4. pus taken from abscesses
5. fluid from the brain back;
6. lung punctures.

Samples must be moved to their destination quickly. Work is carried out in a specialized container, sometimes in a plastic bag.

It must be designed for anaerobic conditions. Because the interaction of samples with atmospheric oxygen can cause the complete death of bacteria. Liquid types of samples are moved in test tubes, sometimes directly in syringes.

If swabs are moved for research, then they are transported only in test tubes with the presence of carbon dioxide, sometimes with pre-made substances.

Anaerobic bacteria are able to develop in the absence of free oxygen in the environment. Together with other microorganisms with a similar unique property, they make up the class of anaerobes. There are two types of anaerobes. Both facultative and obligate anaerobic bacteria can be found in almost all samples of pathological material, they accompany various purulent-inflammatory diseases, can be opportunistic and even sometimes pathogenic.

Anaerobic microorganisms, which are facultative, exist and multiply in both oxygen and anoxic environments. The most pronounced representatives of this class are Escherichia coli, Shigella, Staphylococcus, Yersinia, Streptococcus and other bacteria.

Obligate microorganisms cannot exist in the presence of free oxygen and die from its exposure. The first group of anaerobes of this class is represented by spore-forming bacteria, or clostridia, and the second by bacteria that do not form spores (non-clostridial anaerobes). Clostridia are often the causative agents of anaerobic infections of the same name. An example would be clostridial botulism, tetanus. Non-clostridial anaerobes are gram-positive and They have a rod-shaped or spherical shape, you probably met the names of their brightest representatives in the literature: bacteroids, veillonella, fusobacteria, peptococci, propionibacteria, peptostreptococci, eubacteria, etc.

Non-clostridial bacteria for the most part are representatives of the normal microflora in both humans and animals. They can also participate in the development of purulent-inflammatory processes. These include: peritonitis, pneumonia, abscess of the lungs and brain, sepsis, phlegmon of the maxillofacial region, otitis media, etc. For the bulk of infections caused by non-clostridial anaerobic bacteria, it is typical to exhibit endogenous properties. They develop mainly against the background of a decrease in the body's resistance, which can occur as a result of trauma, cooling, surgery, and impaired immunity.

To explain the method of maintaining the life of anaerobes, it is worth understanding the basic mechanisms by which aerobic and anaerobic respiration occurs.

Represents oxidative process, based on respiration leads to the splitting of the substrate without residue, the result is representatives of the inorganic that are split to energy-poor representatives. The result is a powerful release of energy. Carbohydrates are the most important substrates for respiration, but both proteins and fats can be consumed during aerobic respiration.

It corresponds to two stages of flow. At the first, an oxygen-free process of gradual splitting of the substrate occurs to release hydrogen atoms and bind to coenzymes. The second, oxygen stage, is accompanied by further cleavage from the substrate for respiration and its gradual oxidation.

Anaerobic respiration is carried out by anaerobic bacteria. They use not molecular oxygen to oxidize the respiratory substrate, but a whole list of oxidized compounds. They can be sulfuric, nitric, carbonic acid. During anaerobic respiration, they are converted into reduced compounds.

Anaerobic bacteria that carry out such respiration as the final electron acceptor do not use oxygen, but inorganic substances. According to their belonging to a certain class, several types of anaerobic respiration are distinguished: nitrate respiration and nitrification, sulfate and sulfur respiration, "iron" respiration, carbonate respiration, fumarate respiration.

Dennis L. Kasper

Definition. Anaerobic bacteria are microorganisms that require low oxygen tension for growth and cannot grow on the surface of a dense nutrient medium in the presence of 10% carbon dioxide. Microaerophilic bacteria can grow at its content in the atmosphere in the amount of 10%, as well as under anaerobic or aerobic conditions. Facultative bacteria grow both in the presence of air and in its absence. This chapter focuses on infections caused by non-spore-forming anaerobic bacteria. In general, anaerobes that cause infections in humans are relatively aerotolerant. Microorganisms can survive in the presence of oxygen for 72 hours, although they usually do not multiply in this case. Less pathogenic anaerobic bacteria, which are also part of the normal flora of the human body, die after short-term contact with oxygen, even at low concentrations.

Non-spore-forming anaerobic bacteria are part of the normal microflora of the mucous membranes in humans and animals. The main reservoirs of these bacteria are in the mouth, in the gastrointestinal tract, on the skin, and in the female genital tract. Anaerobes predominate in the microflora of the oral cavity. Their concentration is 10 ^ ml of saliva and up to 10 ^ / ml in scraping from the gums. In the oral cavity, the ratio of anaerobic to aerobic bacteria on the surface of the teeth is 1:1. At the same time, in the slit spaces between the gum and the tooth surface, the number of anaerobic bacteria is 100-1000 times higher than the number of aerobes. In a normally functioning intestine, anaerobic bacteria are not found until the distal ileum. In the large intestine, the proportion of anaerobes increases significantly, as does the total number of bacteria. For example, in the large intestine, 1 g of feces contains 1011-1012 microorganisms with a ratio of anaerobes and aerobes of approximately 1000:1. 1 ml of secretion from the female genital organs contains approximately 109 microorganisms at a ratio of anaerobes and aerobes of 10:1. Several hundred species of anaerobic bacteria have been identified in the normal human microflora. The diversity of the anaerobic flora reflects the fact that up to 500 species of anaerobes have been identified in human feces. However, despite the diversity of bacteria that make up the normal human microflora, a relatively small number of them are detected in infectious diseases.

Anaerobic infections develop when the harmonious relationship between the macro- and microorganism is destroyed. Any organ is susceptible to these microorganisms that constantly vegetate in the body in case of damage to the mucous barriers or skin during operations, after injuries, in tumors or in conditions such as ischemia or necrosis that contribute to a decrease in the local redox potential of tissues. Due to the fact that various types of bacteria grow in the vegetation areas, damage to the anatomical barriers creates opportunities for the introduction of many microorganisms into tissues, which often leads to the development of mixed infections. different types anaerobes, facultative or microaerophilic bacteria. Similar mixed infections occur in the head and neck (chronic sinusitis and otitis media, Ludwig's angina, periodontal abscess). The most common anaerobic infections of the central nervous system include brain abscess and subdural empyema. Anaerobes cause pleuropulmonary diseases such as aspiration and necrotizing pneumonia, abscesses or empyema. Similarly, anaerobes play important role in the development of intra-abdominal processes, such as peritonitis, abscesses, hepatic abscesses. They are often found in infectious diseases of the female genital organs: salpingitis, pelvioperitonitis, tubo-ovarian (tubal-ovarian) and vulvovaginal abscesses, septic abortions and endometritis. Anaerobic bacteria are often identified in infections of the skin, soft tissues, bones, and also cause bacteremia.

Etiology. The classification of these microorganisms is based on the ability to stain according to Gram. Of the anaerobic gram-positive cocci that most often cause disease, peptostreptococci should be noted. Of the Gram-negative anaerobic bacteria, representatives of the bacteroid family, including bacteroids, fusobacteria, and pigmented bacteroids, play the main role. The B. fragilis group includes pathogenic anaerobic bacteria most frequently isolated in clinical infections. Representatives of this group of microorganisms are part of the normal intestinal flora. It includes several species, including bacteroids, B. thetaiotaomicron, B. distasonis, B. vulgaris, and B. ovatis. B. fragilis has the most important clinical significance in this group. However, they are found less frequently in the normal intestinal flora than other types of bacteroids. The second large group is part of the normal flora of the oral cavity. These are primarily pigment-producing bacteria that were originally classified as B. melaninogenicus. Modern terminology to define this group has changed: B. dingivalis, B. asaccharolyticus, and B. melaninogenicus. Fusobacteria have also been isolated in clinical infections, including necrotizing pneumonia and abscesses.

Infections caused by anaerobic bacteria are more commonly caused by mixed flora. The infection may be due to one or more types of anaerobes, or a combination of anaerobic and aerobic bacteria acting synergistically. The concept of mixed infections requires a revision of Koch's postulates, since the position "one microbe - one disease" in many infections is not acceptable in diseases caused by many strains of bacteria acting synergistically.

Approaches to the management of patients with anaerobic bacterial infections. Some important considerations should be kept in mind when approaching the management of a patient with suspected anaerobic infection.

1. Most of the microorganisms are harmless commensals and only a few of them cause disease.

2. In order for them to cause an infection, they must penetrate the mucous membranes.

3. Conditions are necessary that favor the reproduction of these bacteria, especially a reduced redox potential, therefore, infections occur in the area of ​​trauma, tissue destruction, impaired blood supply, or as complications of previous infections that contributed to tissue necrosis.

4. characteristic feature anaerobic infections is the diversity of the infecting flora, for example, up to 12 types of microorganisms can be isolated from individual foci of suppuration.

5. Anaerobic microorganisms are found mainly in abscess cavities or in necrotic tissues. The discovery of an abscess in a patient, from which routine bacteriological examination fails to isolate a microorganism, should alert the doctor that anaerobic bacteria probably vegetate in it. However, often in smears of such "sterile pus" when stained by Gram, a large number of bacteria are determined. The stench of pus is also an important sign of an anaerobic infection. Although some facultative organisms, such as Staphylococcus aureus, can also cause abscesses, an abscess in an organ or deep tissue should nevertheless be suggestive of anaerobic infection.

6. Treatment does not have to be aimed at suppressing all microorganisms in the inflammatory focus. However, with invasion by some types of anaerobic bacteria, specific treatment is required. An example is the need to treat a patient with an infection caused by B. fragilis. Many of these synergists can be suppressed with antibiotics that affect only certain, and not all, representatives of the microflora. The hypothesis is that treatment with antibacterial drugs while draining an abscess destroys the interdependent relationship between bacteria and that antibiotic-resistant organisms cannot survive without the accompanying flora.

7. Manifestations of disseminated intravascular coagulation in patients with infections caused by anaerobic bacteria are usually absent.

Epidemiology. Difficulties in obtaining appropriate cultures, contamination of crops with aerobic bacteria or normal microflora, and the lack of easy, affordable and reliable methods of bacteriological research cause insufficient information about the incidence of anaerobic infections. However, it can be stated that they are often found in hospitals in which surgical, trauma, obstetric and gynecological services are actively functioning. In some centers, anaerobic bacteria are cultured from about 8-10% of patients' blood. In these cases, B. fragilis predominates. The frequency of isolation of anaerobes during crops of various clinical material can reach 50%.

Pathogenesis. Due to the specific growth conditions of these microorganisms and their presence as commensals on the surface of the mucous membranes, the development of infection requires that the microorganisms be able to penetrate the mucous membranes and invade tissues with a reduced redox potential. Therefore, tissue ischemia, trauma, including surgical perforation of internal organs, shock or aspiration provide conditions conducive to the proliferation of anaerobes. Highly demanding anaerobes do not have in their composition the enzyme superoxide bismutase (SOB), which allows other microorganisms to break down toxic superoxide radicals, thereby reducing their effect. A correlation was noted between the intracellular concentration of SOM and the tolerance of anaerobic bacteria to oxygen: microorganisms that have SOM in their composition are distinguished by a selective advantage after exposure to aerobic conditions. For example, when an organ is perforated, several hundred species of anaerobic bacteria enter the abdominal cavity, but many of them do not survive, since the richly vascularized tissue is supplied with oxygen to a sufficient extent. The output of oxygen in environment leads to the selection of aerotolerant microorganisms.

Anaerobic bacteria produce exoenzymes that enhance their virulence. These include heparinase produced by B. fragilis, which may be involved in intravascular coagulation and cause the need for increased doses of heparin in patients receiving it. Collagenase produced by B. meianinogenicus can enhance tissue destruction. Both B. fragilis and B. meianinogenicus produce lipopolysaccharides (endotoxins) that lack some of the biological potencies of endotoxins produced by aerobic Gram-negative bacteria. This biological inactivity of endotoxin may explain the rare occurrence of shock, disseminated intravascular coagulation, and purpura in bacteroid-induced bacteremia compared with bacteremia due to facultative and aerobic Gram-negative rod-shaped bacteria.

B. fragiiis is a unique pathogenic anaerobic bacterial species in its ability to cause abscess formation by acting as the sole pathogenic agent. This microorganism has polysaccharides in its capsule, which determine its virulence. They directly cause abscess formation in experimental models of intra-abdominal sepsis. Other anaerobic species can cause abscess formation only in the presence of synergistically acting facultative microorganisms.

Clinical manifestations. Anaerobic infections in the head and neck. Infections of the oral cavity can be divided into those originating from the structures of the tooth, located above the gums and below them. Supragingival plaques begin to form when Gram-positive bacteria adhere to the tooth surface. Plaques are influenced by saliva and food components, their formation depends on oral hygiene and local protective factors. Once they occur, they eventually lead to the development of gum disease. Early bacteriological changes in plaques located above the gums provoke inflammatory responses in the gums. These changes are manifested by swelling, swelling of the gums and an increase in the amount of fluid in them. They cause the development of caries and intradental infection (pulpitis). These changes also contribute to the development of subsequent lesions in the plaques located under the gums, which are formed when the rules of oral hygiene are not followed. Plaques localized under the gums are directly related to periodontal lesions and disseminated infections emanating from the oral cavity. Bacteria vegetating in the subgingival areas are represented mainly by anaerobes. The most important of these are black pigment-forming gram-negative anaerobic bacteria from the bacteroid group, in particular B. gingivalis and B. meianinogenicus. Infections in this area are often mixed, both anaerobic and aerobic bacteria are involved in their development. Once a local infection develops either in the root canal or in the periodontal area, it can spread to the mandible with subsequent development of osteomyelitis, as well as to the sinuses of the maxilla or to the soft tissues of the submandibular spaces of the maxilla or mandible, depending on the tooth that serves as the source of infection. . Periodontitis can also lead to the spread of infection to adjacent bone formations or soft tissues. This form of infection can be caused by bacteroids or fusobacteria vegetating in the oral cavity.

Inflammation of the gums. Gingivitis can be complicated by a necrotic process (Vincent's spirochetosis, Vincent's stomatitis) - The disease usually begins unexpectedly and is accompanied by the development of bleeding seals on the gums, bad breath, and loss of taste. The mucous membrane of the gums, especially the papillae between the teeth, become ulcerated and may be covered with a gray exudate, which is easily removed with little effort. The disease can take a chronic course, in patients in this case, the body temperature rises, cervical lymphadenopathy and leukocytosis join. Sometimes ulceration from the gums can spread to the mucous membrane of the cheeks, teeth, lower or upper jaw, leading to extensive destruction of bone and soft tissues. This infection is called acute necrotizing ulceration of the mucous membrane (water cancer, noma). It causes rapid destruction of tissue, accompanied by loss of teeth and the transformation into a scab of large areas of bone and even the entire lower jaw. Often it is accompanied by a putrid odor, although the lesions are painless. Sometimes there is a healing of gangrenous foci, after which large shapeless defects remain. Most often, the disease is due to debilitating diseases or severe malnutrition of children in the underdeveloped countries of the world. It is known to complicate leukemia or develop in individuals with a genetically determined catalase deficiency.

Acute necrotizing infections of the pharynx. These infections are combined with ulcerative hypgiitis, although they can develop on their own. The main complaints presented by patients include severe sore throat, shortness of breath and an unpleasant taste in the mouth against the background of difficulty in swallowing and a feverish state. When examining the pharynx, one can see the arches, edematous, hyperemic, ulcerated and covered with a grayish, easily removable film. Usually, lymphadenopathy and leukocytosis are noted. The illness may last for only a few days or persist if not treated. The process is usually unilateral, but may spread to the other side of the pharynx or larynx. Aspiration by patients of infectious material can lead to the development of a lung abscess. Soft tissue infections of the orofacial region may be of odontogenic or non-odontogenic origin. Ludwig's angina, a periodontal infection usually originating in the third molar, can cause submandibular cellulitis, which is marked by localized swelling of the tissues, accompanied by pain, trismus, and anterior and posterior displacement of the tongue. Submandibular swelling develops, which can lead to difficulty swallowing and airway obstruction. In some cases, for health reasons, a tracheostomy is required. In the etiology of the disease, a mixed anaerobic and aerobic infection originating from the oral cavity plays a role.

Fascial infections. These infections develop as a result of the spread of microorganisms in the upper respiratory tract through hidden spaces formed by the fascia of the head and neck. Despite the paucity of confirmed reports on microbiology in these diseases, many bacteriological studies indicate that anaerobes living in the oral cavity are involved in its development. In severe skin infections, such as furunculosis or impetigo, Staphylococcus aureus and pyogenic streptococcus may be involved in the infection of the fascial spaces. At the same time, anaerobic infection is usually associated with lesions of the mucous membranes and dental procedures or occurs spontaneously.

Sinusitis and otitis. Despite the lack of information on the role of anaerobic bacteria in acute sinusitis, it is likely that, due to the inadequate nature of the studied pathological material, the frequency with which anaerobes cause them is often underestimated. Samples for culture are obtained by aspiration through the lower nasal passage without decontamination of the mucous membranes of the nasal cavity. In contrast, there is no controversy regarding the value of anaerobes in chronic sinusitis. Anaerobic bacteria were found in 52% of samples obtained by external frontoethmoidotomy or radical anthrotomy through the canine fossa. These methods avoid contamination of samples with bacteria living on the mucous membranes of the nasal cavity. Similarly, anaerobic bacteria are more likely to cause chronic suppurative otitis media than acute otitis media. It has been established that in chronic otitis in the purulent discharge from the ear, anaerobes are contained in almost 50% of patients. In these chronic infections, a wide variety of anaerobes, mainly of the bacteroid genus, have been isolated. In contrast to other head and neck infections in chronic otitis media, B. fragilis was isolated in 28% of cases.

Complications of anaerobic infections of the head and neck. The spread of these infections in the cranial direction can lead to osteomyelitis of the bones of the skull or mandible, or to the development of an intracranial infection such as a brain abscess or subdural empyema. Caudal spread of infection may cause mediastinitis or pleuropulmonary disease. Anaerobic infections of the head and neck can be spread by the hematogenous route. There are known cases of bacteremia, when numerous types of bacteria serve as an etiological factor, in which endocarditis or other distant focus of infection can develop. With purulent phlebitis of the internal jugular vein, due to the spread of infection, a destructive syndrome can develop with a prolonged increase in body temperature, bacteremia, purulent embolism of the vessels of the lungs and brain, and multiple metastatic purulent foci. However, in the era of antibiotics, this disease, known as Lameer's post-anginal septicemia, is rare.

Infections of the central nervous system. Of the many infectious diseases of the central nervous system, anaerobes most often cause brain abscesses. When using the most effective methods bacteriological examination in 85% of abscesses anaerobic flora can be detected, and gram-positive anaerobic cocci are especially common, less often fusobacteria and certain types bacteroids. Often, facultative or microaerophilic streptococci or Escherichia coli are found in the mixed flora of brain abscesses. A brain abscess is formed as a result of the spread of purulent processes from the paranasal cavities, the mastoid process or the middle ear, or with foci of infection in distant organs, especially in the lungs, spreading by hematogenous route. Brain abscesses are discussed in more detail in Chap. 346.

Diseases of the pleura and lungs. These diseases are caused by aspiration of the contents of the oropharynx, most often in violation of consciousness or the absence of a gag reflex. There are four known clinical syndromes associated with aspiration-induced anaerobic infections of the pleura and lungs: simple aspiration, necrotizing pneumonia, abscess, and empyema.

Anaerobic aspiration pneumonia. Anaerobic aspiration pneumonia must be differentiated from the other two types of aspiration pneumonia that are not of bacterial origin. One of the aspiration syndromes is caused by the aspiration of solid masses, usually food. In these cases, obstruction of the main airways occurs due to developing atelectasis. Moderately expressed nonspecific inflammation develops. Treatment consists of removing the foreign body.

Another aspiration syndrome is more easily mistaken for aspiration of infected masses. This is the so-called Mendelssohn's syndrome as a result of reflux of gastric contents and aspiration. chemical compounds, most often gastric juice. In this case, inflammation of the lungs develops very quickly, causing destruction of the alveolar structures with extravasation of fluid into their lumen. Usually the syndrome develops within a few hours, often after anesthesia, when the gag reflex is suppressed. The patient develops tachypnea, hypoxia and febrile condition. The number of leukocytes may increase, and the radiographic picture may suddenly change within 8-24 hours (from normal to complete bilateral darkening of the lungs). Sputum is excreted in minimal quantities. With symptomatic treatment, changes in the lungs and symptoms can quickly level out, or respiratory failure develops within a few days, followed by bacterial superinfection. Antibiotic treatment is not indicated until a bacterial infection has developed. Its signs include sputum, persistent fever, leukocytosis, clinical manifestations of sepsis.

In contrast to these syndromes, bacterial aspiration pneumonia develops more slowly, and in hospitalized patients with a suppressed gag reflex, in elderly patients, or with transient impairment of consciousness as a result of a nervous attack or alcohol intoxication. People hospitalized with this syndrome usually have been ill for several days by this time, they complain of a slight increase in body temperature, a feeling of malaise and sputum production. There is usually a history of predisposing factors for aspiration, such as alcohol overdose or nursing home stay. Characteristically, during at least the first week of illness, sputum does not have an unpleasant odor. Her Gram-stained smear revealed a mixed bacterial flora with a large number of polymorphonuclear leukocytes. Reliable data on the causative agent of the disease can only be obtained by inoculating samples that are not contaminated with the microflora of the oral cavity. These samples can be obtained by aspiration through the trachea. X-ray of the organs of the chest cavity can reveal the compaction of certain segments of the lungs. These include the hilar areas of the lower lobes, if the aspiration occurred while the patient was in an upright position or in a sitting position (usually in the elderly), or in the posterior segment of the upper lobe, usually on the right, or in the upper segment of the lower lobe, if the aspiration occurred during the position of the patient on the back. The microorganisms allocated at the same time reflect the normal composition of the microflora of the pharynx (B. melaninogenicus, fusobacteria and anaerobic cocci). Patients who have had aspiration in a hospital may have a mixed microflora, including facultative E. coli gram-negative.

Necrotizing pneumonia. This form of anaerobic pneumonia is characterized by numerous but small abscesses spreading over several lung segments. The process can be sluggish or lightning fast. It is less common than aspiration pneumonia or lung abscess and may present as such. just like them.

Anaerobic lung abscesses. They develop in association with a subacute lung infection. Typical features of clinical symptoms include feeling unwell, weight loss, fever, chills, sputum with an unpleasant odor, sometimes for several weeks. The patient usually suffers from infectious diseases of the teeth or periodontitis, but there are reports of the development of lung abscesses in patients who have no teeth. Abscesses can be single or multiple, but usually they are localized in the affected segment of the lung. Despite the similarity in clinical symptoms with other abscesses, anaerobic ones can be differentiated from tuberculous, neoplastic, etc. Anaerobes of the oral cavity predominate in the microflora, although B. fragilis, sometimes Staphylococcus aureus, are sown in almost 10% of patients. Despite the fact that B. fragilis is resistant to penicillin in vitro, it is usually successfully used in anaerobic lung abscesses against the background of their vigorous debridement. It is likely that the effect of penicillin is due to the synergistic nature of the infection. Bronchoscopy is indicated only to establish airway obstruction, but should be delayed until the antibiotics are effective so that bronchoscopy does not contribute to the mechanical spread of infection. Bronchoscopy does not increase the drainage function. Surgical treatment is almost never indicated and can even be dangerous due to the possibility of abscess contents entering the lung tissue.

Empyema. With prolonged anaerobic infection of the lungs, empyema develops. It resembles other anaerobic lung infections in clinical manifestations, including foul-smelling sputum. The patient may complain of pleural pain and severe chest pain.

Empyema may be masked by severe pneumonia and may be suspected every time a persistent fever persists despite treatment. A thorough physical examination and ultrasonography are important for diagnosis because they can locate a localized empyema. Thoracocentesis usually results in a foul-smelling exudate. The cavity needs to be drained. Recovery, normalization of the condition and resolution of the inflammatory process can occur after several months of treatment, both with empyema and lung abscess.

Anaerobic empyema may also be due to the spread of infection from the subdiaphragmatic space. Septic pulmonary emboli may originate from sites of infection in the abdominal cavity or in the female genital organs. These emboli can cause the development of anaerobic pneumonia.

Infections of the abdominal organs. Due to the fact that in the composition of the normal intestinal flora the number of anaerobic bacteria is 100-1000 times higher than the number of aerobic ones, it is not surprising that damage to the intestinal wall leads to peritonitis of predominantly anaerobic etiology. Perforation of the colonic wall allows large numbers of these bacteria to enter the abdominal cavity and is therefore associated with a high risk of intra-abdominal sepsis. As a consequence of peritonitis, abscesses can develop in any part of the abdominal cavity and retroperitoneal space. The peritoneum reacts with a pronounced inflammatory reaction and is effectively freed from infection in a short time. If an intra-abdominal abscess is localized, then it appears typical signs and symptoms (see ch. 87). For example, a subdiaphragmatic abscess may cause a sympathetic pleural effusion on the corresponding side, and a patient on the same side may develop pleural pain and flattening of the dome of the diaphragm. Typical symptoms include fever, chills, and malaise. The anamnesis has indications of abdominal surgery, trauma, or other causes predisposing to a violation of the integrity of the intestinal wall. In the event that an intra-abdominal abscess forms gradually, the clinical signs of its development may be more blurred. Peritonitis and abscess formation are two closely related processes. Often, after an operation aimed at eliminating the perforation of the intestinal wall, the patient may maintain a febrile body temperature for a long period without local signs of an abdominal process or a general deterioration in the condition. Persistent leukocytosis may be associated directly with surgery and/or resolving peritonitis. The attention of the doctor should be directed to the wound discharge. If it is profuse, cloudy, or offensive, an anaerobic infection may be suspected. A Gram-stained smear, which shows a mixed intestinal flora, is often helpful in diagnosis. B. fragilis is sown in approximately 70% of cases of surgical wounds after trauma, accompanied by perforation of the wall of the lower intestine, the percentage of their detection after surgical interventions on the large intestine is similar. An important role in the treatment is played by antibiotics, which are effective for infection with B. fragilis and facultative bacteria, although they cannot replace surgical or percutaneous drainage of the lesion. The most common source of intra-abdominal anaerobic infection is perforated appendicitis leading to abscess formation. Diverticulitis mediated by non-spore-forming anaerobes can lead to perforation followed by generalized peritonitis, but usually results in small, unrestricted foci of infection that do not require surgical drainage. Abdominal ultrasonography, gallium or indium scanning, computed tomography, or a combined liver, spleen, and lung scan may be helpful to clarify the location of abscesses in the abdomen. However, to establish the exact localization of the infection, surgical examination of the abdominal cavity may be necessary.

Of the infections of the internal organs of the abdominal cavity, caused by non-spore-forming anaerobic bacteria, liver abscesses are most common. Liver abscess can be caused both by bacteremic spread of infection (sometimes after blunt trauma with localized infarction of the liver tissue) and by contact, especially within the abdominal cavity. Infection can spread from the biliary tract or the portal venous system (purulent pylephlebitis), into which it enters with sepsis in the pelvic or abdominal cavity. Symptoms and signs suggest an infection that can be quickly localized, but many patients develop fever, chills, and weight loss associated with nausea and vomiting. In only half of patients, the size of the liver increases, soreness in the right upper quadrant of the abdomen and jaundice appear. Diagnosis can be confirmed by ultrasound, computed tomography, or radioisotope scanning. Sometimes it is necessary to resort to the help of several diagnostic procedures. More than 90% of patients with liver abscesses have leukocytosis and an increase in serum alkaline phosphatase and aspartate transaminase levels, 50% have concomitant anemia, hypoalbuminemia and elevated level serum bilirubin. On a chest x-ray, one can see an infiltrate in the basal parts of the lung, a pleural effusion and an increase in the dome of the diaphragm on the corresponding side. 1/3 of patients develop bacteremia. If the abscess is associated with other purulent foci requiring drainage, open surgical drainage is indicated. Otherwise, percutaneous drainage with ultrasound or computed tomography assessment of catheter position is used. Percutaneous drainage can be performed during antibiotic treatment. If a liver abscess develops as a result of the spread of infection from the gallbladder, cholecystectomy is very effective.

Pelvic infections. The vagina of a healthy woman is one of the main reservoirs of both anaerobic and aerobic flora. In the composition of the normal flora of the female genital tract, the number of anaerobes exceeds the number of aerobic bacteria by approximately 10:1. Anaerobes are dominated by Gram-positive cocci and Bacteroides sp. In severe infections of the upper sections of the female genital tract, microorganisms that make up the normal vaginal flora are secreted. In most patients, anaerobes are isolated, the main pathogenic representatives of which are B. fragilis, B. melaninogenicus, anaerobic cocci and clostridia. Anaerobic bacteria are often found in tubal-ovarian abscesses, septic abortions, pelvic abscesses, endometritis, and postoperative wound infections, especially after hysterectomy. Although these functions are often mixed (anaerobes and intestinal bacteria), "pure" anaerobic infection (no intestinal flora or other facultative bacteria) is much more common in pelvic infections than in intra-abdominal infections. These infections are characterized by discharge of foul-smelling pus or blood from the uterus, widespread soreness in the uterine region or localized soreness in the pelvic cavity, prolonged fever and chills. Infections of the pelvic organs can be complicated by purulent thrombophlebitis of the pelvic veins, which leads to a recurrence of septic embolism in the lungs.

Skin and soft tissue infections. Damage to the skin, bones, or soft tissues during trauma, ischemia, or surgery is a favorable environment for the development of anaerobic infection. The latter most commonly develop in areas most prone to contamination by feces or upper respiratory secretions. These include wounds associated with bowel surgery, bedsores, and human bites. Anaerobic bacteria can be isolated from patients with crepitating cellulitis, synergistic cellulitis or gangrene, and necrotizing fasciitis. Moreover, these microorganisms have been isolated from abscesses of the skin, rectum, and sweat glands (hidradenitis suppurativa). Anaerobes are often isolated from foot ulcers in diabetic patients. In these types of skin and soft tissue infections, a mixed flora is usually found. On average, several bacterial species are isolated from each purulent focus with a ratio of anaerobes and aerobes of the order of 3:2. Most often these are Bacteroides spp., anaerobic streptococci, group D streptococci, clostridium and proteus. Anaerobic infection is more often accompanied by an increase in body temperature, the appearance of foci with fetid discharge, visible ulcers on the feet.

Typically, Meleney's anaerobic bacterial synergistic gangrene develops a few days after surgery. This disease is manifested by a focus of wound infection with acute pain, hyperemia, swelling, followed by its induration. Erythema surrounds the central zone of necrosis. A granulomatous ulcer forms in the center of the lesion, which can heal, while necrosis and erythema spread to the periphery of the lesion. Symptoms are limited to pain. Fever is not typical. The causative agent is most often an association of anaerobic cocci and Staphylococcus aureus. Treatment consists of surgical removal of necrotic tissue and administration of antibiotics.

Necrotizing fasciitis. This is a rapidly spreading destruction of the fascia, usually caused by group A streptococci, but occasionally by anaerobic bacteria, including peptostreptococci and bacteroides. Similarly, myonecrosis may be associated with mixed anaerobic infection. Fournier's gangrene is an anaerobic cellulitis spreading to the scrotum, perineum and anterior abdominal wall, in which a mixed anaerobic microflora spreads through deep fascial spaces and causes extensive skin lesions.

Bone and joint infections. Despite the fact that actinomycosis (see Chapter 147) is considered worldwide to be the basis (background) of most anaerobic bone infections, other microorganisms are often isolated from these infections. Especially widespread are anaerobic or microaerophilic cocci, Bacteroides spp., Fusobacteria and Clostridia. Soft tissues adjacent to the foci of infection are often infected. Bacteroids living in the oral cavity are often found in the infectious process in the upper and lower jaws, while clostridia are considered the main anaerobic pathogen in osteomyelitis after a fracture or injury of long bones. tubular bones. Fusobacteria can be isolated in pure culture in osteomyelitis localized in the paranasal sinuses. In the pre-antibiotic era, they were isolated from mastoiditis, ending in the death of the patient. It has been established that anaerobic and microaerophilic cocci are among the main causative agents of infections of the bone tissue of the skull and mastoid process.

In anaerobic septic arthritis, Fusobacterium spp. In most patients, peritonsillar infections remain undiagnosed, with the progression of which develops septic thrombophlebitis of the cervical veins. The latter is characterized by a tendency to hepatogenic dissemination with a predominant lesion of the joints. In most cases, these infections occurred in the pre-antibiotic era. After the introduction of antibiotics into medical practice, fusobacteria from the joints began to be sown much less frequently. Unlike anaerobic osteomyelitis, in most cases, purulent arthritis caused by anaerobes does not have a polybacterial etiology; it may be due to hematogenous spread of the infection. Anaerobes are important pathogenic agents of infectious lesions of articular prostheses. In this case, the causative agents of infection are usually representatives of the normal microflora of the skin, in particular anaerobic gram-positive cocci and P. acnes.

In patients with osteomyelitis, the most informative method for determining the etiological agent is a bone tissue biopsy taken through uninfected skin and subcutaneous tissues. If a mixed flora is detected in a bone biopsy, treatment is prescribed with a drug that affects all isolated microorganisms. If the main or only pathogenic agent isolated from the affected joint is anaerobe, treatment should not differ from that in the treatment of a patient with arthritis caused by aerobic bacteria. Treatment should be aimed at controlling the underlying disease, using appropriate antibiotics, temporary immobilization of the joint, percutaneous drainage of the joint cavity, and usually removal of infected prostheses or internal fixation devices. In treatment, surgical drainage and removal of diseased tissue (such as sequestrectomy) that can support anaerobic infection is essential.

bacteremia. Transient bacteremia is a well-known condition healthy person when anatomical mucous barriers are damaged (for example, when brushing teeth). These episodes of bacteremia, often caused by anaerobes, usually have no pathological consequences. However, with adequate culture techniques, anaerobic bacteria in a person with clinical manifestations of bacteremia account for 10-15% of microorganisms isolated from the blood. The single most commonly isolated microorganism is B. fragilis. The entry gate of infection can be established by identifying the microorganism and determining its habitats from which it enters the bloodstream. For example, bacteremia caused by mixed anaerobic microflora, including B. fragilis, usually develops in the pathology of the large intestine with damage to its mucous membrane (malignant neoplasms, diverticulitis, or other inflammatory processes). The initial manifestations of the disease are determined by the site of infection and the response of the body. However, if microorganisms enter the bloodstream, the patient may develop an extremely serious condition with chills and hectic body temperature reaching 40.5 ° C. The clinical picture may be no different from that of aerobic sepsis caused by Gram-negative bacteria. However, other complications of anaerobic bacteremia are known, such as septic thrombophlebitis and septic shock, the incidence of which is low in anaerobic bacteremia. Anaerobic bacteremia is often fatal, so prompt diagnosis and appropriate treatment are essential. The source of bacteremia should also be identified. The choice of antibiotic depends on the results of identification of the microorganism.

Endocarditis (see Ch. 188). Anaerobic endocarditis is rare. However, anaerobic streptococci, which are often misclassified, cause the disease much more often than thought, although the overall incidence is unknown. Gram-negative anaerobes rarely cause endocarditis.

Diagnostics. Because of the difficulty in isolating anaerobic bacteria and the time required to isolate them, the diagnosis of anaerobic infections must often be based on speculation. Infections caused by these non-spore-forming anaerobic bacteria have features that greatly facilitate diagnosis. The diagnosis of anaerobic infection is facilitated by the identification of certain clinical signs, in particular non-vascularized necrotic tissues with a reduced redox potential. When identifying the pathogen in foci of inflammation remote from mucous surfaces, normally populated by anaerobic microflora (gastrointestinal tract, female genital tract or oropharynx), anaerobes should be considered a potential etiological agent. With anaerobic infections, an unpleasant odor often appears, since certain organic acids are produced in the process of proliferation in necrotic tissues. Although the odor is pathognomonic for an anaerobic infection, its absence does not exclude the possibility that anaerobes are the cause of the disease. In 50% of cases with anaerobic infection, a characteristic unpleasant odor is absent. Because anaerobes often associate with other bacteria, causing mixed or synergistic infection, Gram-stained exudates often show numerous pleomorphic cocci and suspect anaerobes. Sometimes these microorganisms have morphological characteristics inherent in certain bacterial species.

Gas in the tissues refers to the signs, in the highest degree suspicious for infection with anaerobes, but having no diagnostic value. The results of bacteriological studies of samples from obviously infected foci in which bacterial growth is not detected or only streptococci or one type of aerobes, such as Escherichia coli, are detected, and mixed microflora is found in Gram-stained smears from the same material, mean that anaerobic microorganisms do not grow due to inadequate transport conditions or seeding method. Similarly, the failure of antibacterial drugs that do not have activity against anaerobes, such as aminoglycosides or sometimes penicillin, cephalosporins, or tetracyclines, suggests the possibility of anaerobic infection.

In the diagnosis of anaerobic infection, three decisive conditions are distinguished: 1) obtaining appropriate samples; 2) their fast delivery in microbiological laboratory preferably in an environment designed for the transport of anaerobes; 3) appropriate processing of samples in the laboratory. Sampling for research is carried out with great care directly from the affected area with maximum protection from contamination by normal flora. If a sample is suspected to be contaminated with the normal flora of the body, it cannot be sent for examination to a bacteriological laboratory. Among the samples not suitable for bacteriological examination to detect anaerobic microflora, include: 1) sputum obtained by spontaneous excretion, or discharge from the nose or trachea; 2) samples obtained during bronchoscopy; 3) samples obtained directly from the vaginal vaults; 4) urine obtained from free urination; 5) feces. Samples that can be cultured include blood, pleural fluid, transtracheal aspirates, pus obtained by direct aspiration from an abscess cavity, centesis fluid, suprapubic bladder aspirate, cerebrospinal fluid, and lung aspirates. .

Due to the fact that even short-term exposure to oxygen can cause the death of these microorganisms and prevent their isolation in the laboratory, air must be removed from the abscess cavities from which the contents are taken with a syringe for research, and the needle should be closed with a sterile rubber cap. The resulting sample can be placed in sealed containers with reduced nutrient medium or immediately transferred in a sealed syringe to the laboratory for direct bacteriological examination. Swab sampling should not be practiced. However, if a smear is required, the sample is placed in a reduced semi-liquid medium for delivery to the laboratory. It is important to remember that delays in transport may result in failure to isolate anaerobes due to exposure to oxygen or overgrowth of facultative microorganisms that can inhibit growth or completely destroy the anaerobes contained in the sample. If an anaerobic infection is suspected, Gram-stained smears are prepared from all samples and examined to identify microorganisms with a typical anaerobic morphology. This is important for microorganisms that are detected by Gram staining, but not sown. If the pus is considered "sterile" on examination, or if a Gram stain reveals microorganisms that do not grow on the nutrient medium, anaerobic infection and a violation of the transport conditions or the method of examination should be suspected.

Treatment. The effectiveness of treatment for anaerobic infections is achieved with a combination of appropriate antibiotics, surgical resection and drainage. Although surgery alone can have a decisive effect, it alone may not be sufficient. Abscess cavities should be drained immediately as soon as the focus is localized or fluctuation appears. Perforations should be closed immediately, non-viable tissue or foreign bodies removed, closed spaces are drained, areas of tissue compression are decompressed and conditions are created for adequate blood supply. At the same time, appropriate antibiotics should be used, since anaerobic sepsis can continue after surgery, manifesting itself with intermittent symptoms and latent progression of the process. Often there is a need to start antibiotic treatment based only on the suspicion of an anaerobic infection, without waiting for the results of bacteriological examination and determination of the sensitivity of the microorganism. The choice of antibiotic for initial treatment should be based on knowledge of the causative agent that causes certain clinical manifestations, as well as on bacterioscopic examination of Gram-stained smears, suggesting the participation of certain types of microorganisms. Due to the fact that mixed microflora, in particular intestinal bacteria and other facultative microorganisms, is actively involved in the development of many anaerobic infections, it is desirable to use drugs that act on both anaerobic and aerobic pathogens. In general, if an anaerobic infection is suspected, the choice of antibiotic can be justified quite reliably, since the sensitivity of some anaerobic species to drugs is already known. Since B. fragilis is resistant to penicillin, the main question is whether it is involved in the inflammatory process. In general terms, B. fragilis does not play a significant role in infections above the level of the diaphragm, including infections of the head and neck, pleura and lungs, and central nervous system.

However, in septic processes that develop below the level of the diaphragm, including in the pelvic and abdominal cavities, B. fragilis often takes an active part, and therefore requires treatment with antibiotics that have a detrimental effect on this microorganism.

Since B. fragilis is rarely isolated or has a questionable role in infections in which the primary focus is localized above the level of the diaphragm, penicillin G is most widely used. Recommended doses vary depending on the location of the infection and its severity. So, with lung abscesses, 6-12 million units / day are recommended for at least 4 weeks (see Chapter 205). Infections caused by microorganisms vegetating in the oral cavity are often insensitive to penicillin. In such cases, drugs effective against penicillin-resistant anaerobes, in particular clindamycin, chloramphenicol, (levomycetin) or cefoxitin, should be used. The failure of this type of treatment may explain the reports of increasing resistance of B. mclaninogenicus to penicillin.

Infections originating in the large intestine are probably due to B. fragilis and represent another problem. Numerous therapeutic failures have been reported in patients with confirmed B. fragilis infection treated with penicillin or first-generation cephalosporins. When conducting basic studies in septic processes in the abdominal cavity, it was shown that antibiotics, effective in infection with anaerobic bacteria, significantly reduced the incidence of postoperative infectious complications, including severe ones. Based on these data, it is obvious that if bacteroid involvement in the pathological process is suspected, appropriate treatment should be started immediately. Although the number of antibacterial drugs effective against B. fragilis is limited, there is always a choice, but none of the methods has a clear advantage over the other. In general, with appropriate antibiotic therapy, more than 80% of patients with B. fragilis infection can recover.

Many medications from among those routinely available to the physician may be considered potentially useful in infections caused by B. fragilis. These include clindamycin, metronidazole, and cefoxitin. At the same time, although chloramphenicol (levomycetin) is known to be effective in some intra-abdominal infections and infectious diseases of the pelvic organs in women, there are separate reports of treatment failures, including persistent bacteremia caused by B. fragilis. Cefamandole, cefocerazone, cefotaxime and moxalactam, at significantly lower concentrations than the other antibiotics mentioned, inhibit this microorganism.

The treatment regimen for specific infections should strictly correspond to the primary localization of the process and the clinical picture. For example, a patient with intra-abdominal sepsis should be treated with either clindamycin (600 mg IV every 8 hours) or metrondazole (7.5 mg/kg every 8 hours). Aminoglycosides (gentamicin, tobramycium) are recommended to be included in the treatment regimen for gram-negative bacterial infections. Cefoxitin is more effective than clindamycin and amipoglycosides in severe/s mixed infections of the abdominal cavity and skin, the etiology of which [often involves B. fragilis. However, in patients receiving or previously treated with antibacterial drugs or with nosocomial infections, an aminoglycoside should be added to cefoxitin. This is due to the fact that the patient in this case is at high risk of infections caused by microorganisms resistant to cefoxite, such as Enterobacteriaceae, Pseudomonas or Serratia.

Chloramphenicol (levomycetin) can be treated in patients with infections of the abdominal cavity or central nervous system at a dose of 30-60 mg/kg per day, depending on the severity of the infection. The drug is effective in infections of the central nervous system caused by anaerobic bacteria. Penicillin G and metronidazole also easily penetrate the vascular wall and the spinal barrier and have bactericidal properties against bacteria that cause the development of brain abscesses. Patients with meningitis or endocarditis due to anaerobic bacteria are also preferably treated with bactericides.

Although other semi-synthetic penicillinase-resistant penicillins are inactive against anaerobes, carbenicillin, ticarcillin and piperacillin, which have the same spectrum of activity as penicillin G, are active against B. fragilis and are effective when used at higher doses. Despite the fact that this group of antibiotics is not recommended as first-line drugs for anaerobic infections, they have been effective in some cases.

Almost all of the antibiotics mentioned cause certain toxic reactions. Chloramphenicol (levomycetin) causes fatal aplastic anemia in one in 40,000 to 100,000 patients. Clindamycin, cephalosporins, nonicillins, and sometimes metronidazole have been linked to the development of pseudomembranous colitis caused by Clostridium. Because diarrhea may precede the development of pseudomembranes, these drugs should be discontinued immediately.

Due to widespread drug resistance, tetracycline and doxycycline should not be used for anaerobic infections. Erythromycin and vancomycin have some activity in Gram-positive anaerobic infections, but are not recommended for severe infections.

In infections caused by anaerobes, in which treatment is ineffective or relapse occurs after primary treatment, a second bacteriological examination is mandatory. The need for surgical drainage and excision of dead tissue should also be reconsidered. With the development of superinfection, it can be assumed that it is caused by drug-resistant gram-negative facultative or anaerobic bacteria. It is also necessary to take into account the drug resistance of the pathogen, especially if the treatment is carried out with chloramphenicol (levomycetin). With repeated bacteriological examination, it is necessary to isolate the causative agent of infection.

Other additional measures for the treatment of patients with anaerobic infection include careful monitoring of electrolyte and water balance, since the development of severe local edema can cause hypovolemia, as well as hypodynamic measures in the development of septic shock, if necessary, immobilization of the limbs, maintaining appropriate nutrition in chronic infections by enteral or parenteral administration of nutrients, administration of painkillers, anticoagulants (heparin for thrombophlebitis). Hyperbaric oxygen therapy is of no value in anaerobic infections.

Bacteria are present everywhere in our world. They are everywhere and everywhere, and the number of their varieties is simply amazing.

Depending on the need for the presence of oxygen in the nutrient medium for the implementation of vital activity, microorganisms are classified into the following types.

• Obligate aerobic bacteria, which are collected in the upper part of the nutrient medium, the flora contained the maximum amount of oxygen.
• Obligate anaerobic bacteria, which are located in the lower part of the environment, as far as possible from oxygen.
• Facultative bacteria mainly live in the upper part, but can be distributed throughout the environment, as they do not depend on oxygen.
• Microaerophiles prefer a low concentration of oxygen, although they gather in the upper part of the environment.
• Aerotolerant anaerobes are evenly distributed in the nutrient medium, insensitive to the presence or absence of oxygen.

The concept of anaerobic bacteria and their classification

The term "anaerobes" appeared in 1861, thanks to the work of Louis Pasteur.

Anaerobic bacteria are microorganisms that develop regardless of the presence of oxygen in the nutrient medium. They get energy by substrate phosphorylation. There are facultative and obligate aerobes, as well as other types.

The most significant anaerobes are bacteroides

The most important aerobes are bacteroids. Approximately fifty percent of all purulent-inflammatory processes, the causative agents of which can be anaerobic bacteria, are bacteroids.

Bacteroides are a genus of Gram-negative obligate anaerobic bacteria. These are rods with bipolar coloration, the size of which does not exceed 0.5-1.5 by 15 microns. They produce toxins and enzymes that can cause virulence. Different bacteroids have different resistance to antibiotics: there are both resistant and susceptible to antibiotics.

Energy production in human tissues

Some tissues of living organisms have increased resistance to low oxygen content. Under standard conditions, the synthesis of adenosine triphosphate occurs aerobically, but with increased physical exertion and inflammatory reactions, the anaerobic mechanism comes to the fore.

Adenosine triphosphate (ATP) It is an acid that plays an important role in the body's energy production. There are several options for the synthesis of this substance: one aerobic and as many as three anaerobic.

Anaerobic mechanisms of ATP synthesis include:

• rephosphorylation between creatine phosphate and ADP;
• transphosphorylation reaction of two ADP molecules;
• anaerobic breakdown of blood glucose or glycogen stores.

Cultivation of anaerobic organisms

There are special methods for growing anaerobes. They consist in replacing air with gas mixtures in sealed thermostats.

Another way is to grow microorganisms in a nutrient medium to which reducing substances are added.

Culture media for anaerobic organisms

There are common nutrient media and differential diagnostic nutrient media. Common ones include the Wilson-Blair medium and the Kitt-Tarozzi medium. For differential diagnostic - Hiss medium, Ressel medium, Endo medium, Ploskirev medium and bismuth-sulfite agar.

The basis for the Wilson-Blair medium is agar-agar with the addition of glucose, sodium sulfite and iron dichloride. Black colonies of anaerobes are formed mainly in the depth of the agar column.

Ressel's (Russell's) medium is used in the study of the biochemical properties of bacteria such as Shigella and Salmonella. It also contains agar-agar and glucose.

Wednesday Ploskirev inhibits the growth of many microorganisms, so it is used for differential diagnostic purposes. In such an environment, pathogens of typhoid fever, dysentery and other pathogenic bacteria develop well.

The main purpose of bismuth sulfite agar is the isolation of salmonella in its pure form. This environment is based on the ability of Salmonella to produce hydrogen sulfide. This medium is similar to the Wilson-Blair medium in the technique used.

Anaerobic infections

Most anaerobic bacteria living in the human or animal body can cause various infections. As a rule, infection occurs during a period of weakened immunity or a violation of the general microflora of the body. There is also the possibility of infection pathogens from the external environment, especially in late autumn and winter.

Infections caused by anaerobic bacteria are usually associated with the flora of the human mucous membranes, that is, with the main habitats of anaerobes. Typically, these infections multiple triggers at once(to 10).

The exact number of diseases caused by anaerobes is almost impossible to determine due to the difficulty in collecting materials for analysis, transporting samples, and cultivating the bacteria themselves. Most often, this type of bacteria is found in chronic diseases.

Anaerobic infections affect people of all ages. At the same time, the level of infectious diseases in children is higher.

Anaerobic bacteria can cause various intracranial diseases (meningitis, abscesses, and others). Distribution, as a rule, occurs with the blood stream. In chronic diseases, anaerobes can cause pathologies in the head and neck: otitis media, lymphadenitis, abscesses. These bacteria are dangerous to both the gastrointestinal tract and the lungs. With various diseases of the urogenital female system, there is also a risk of developing anaerobic infections. Various diseases of the joints and skin can be the result of the development of anaerobic bacteria.

Causes of anaerobic infections and their symptoms

Infections are caused by all processes during which active anaerobic bacteria enter the tissues. Also, the development of infections can cause impaired blood supply and tissue necrosis (various injuries, tumors, edema, vascular disease). Mouth infections, animal bites, lung diseases, pelvic inflammatory disease and many other diseases can also be caused by anaerobes.

In different organisms, the infection develops in different ways. This is influenced by the type of pathogen, and the state of human health. Because of the difficulties associated with diagnosing anaerobic infections, the conclusion is often based on assumptions. They differ in some features of the infection caused by non-clostridial anaerobes.

The first signs of infection of tissues with aerobes are suppuration, thrombophlebitis, gas formation. Some tumors and neoplasms (intestinal, uterine and others) are also accompanied by the development of anaerobic microorganisms. With anaerobic infections, an unpleasant odor may appear, however, its absence does not exclude anaerobes as the causative agent of the infection.

Features of obtaining and transporting samples

The very first study in determining infections caused by anaerobes is a visual inspection. Various skin lesions are a common complication. Also, evidence of the vital activity of bacteria will be the presence of gas in infected tissues.

For laboratory research and establishing an accurate diagnosis, first of all, it is necessary to competently get matter sample from the affected area. For this, a special technique is used, thanks to which normal flora does not get into the samples. The best method is aspiration with a straight needle. Obtaining laboratory material by smears is not recommended, but possible.

Samples not suitable for further analysis include:

• sputum obtained by self-excretion;
• samples obtained during bronchoscopy;
• smears from the vaginal vaults;
• urine with free urination;
• feces.

For research can be used:

• blood;
• pleural fluid;
• transtracheal aspirates;
• pus obtained from the abscess cavity;
• cerebrospinal fluid;
• lung punctures.

Transport samples it is necessary as soon as possible in a special container or plastic bag with anaerobic conditions, since even a short-term interaction with oxygen can cause the death of bacteria. Liquid samples are transported in a test tube or in syringes. Swabs with samples are transported in test tubes with carbon dioxide or pre-prepared environments.

In the case of diagnosing an anaerobic infection for adequate treatment, it is necessary to follow the following principles:

• toxins produced by anaerobes must be neutralized;
• the habitat of bacteria should be changed;
• the spread of anaerobes must be localized.

To comply with these principles antibiotics are used in treatment, which affect both anaerobes and aerobic organisms, since often the flora in anaerobic infections is mixed. At the same time, when prescribing drugs, the doctor must evaluate the qualitative and quantitative composition of the microflora. The agents that are active against anaerobic pathogens include: penicillins, cephalosporins, champhenicol, fluoroquinolo, metranidazole, carbapenems and others. Some drugs have a limited effect.

To control the habitat of bacteria, in most cases, surgical intervention is used, which is expressed in the treatment of affected tissues, drainage of abscesses, and ensuring normal blood circulation. Surgical methods should not be ignored because of the risk of life-threatening complications.

Sometimes used ancillary therapies, and also because of the difficulties associated with the exact determination of the causative agent of the infection, empirical treatment is used.

With the development of anaerobic infections in the oral cavity, it is also recommended to add as many fresh fruits and vegetables to the diet as possible. The most useful are apples and oranges. The restriction is subjected to meat food and fast food.