Anaerobic infection

Wound anaerobic infection attracts close attention of surgeons, infectious disease specialists, microbiologists and other specialists. This is due to the fact that anaerobic infection occupies a special place due to the exceptional severity of the disease, high mortality (14-80%), frequent cases of deep disability of patients. Anaerobes and their associations with aerobes currently occupy one of the leading places in human infectious pathology.

Anaerobic infection can develop as a result of trauma, surgery, burns, injections, as well as complicated acute and chronic purulent diseases of soft tissues and bones, vascular diseases against the background of atherosclerosis, diabetic angioneuropathy. Depending on the cause of the infectious disease of soft tissues, the nature of the damage and its localization, anaerobic microorganisms are detected in 40-90% of cases. Thus, according to some authors, the frequency of anaerobes in bacteremia does not exceed 20%, and in phlegmon of the neck, odontogenic infection, intra-abdominal purulent processes it reaches 81-100%.

Traditionally, the term "anaerobic infection" referred only to infections caused by clostridia. However, in modern conditions, the latter are not so often involved in infectious processes, only in 5-12% of cases. The main role is given to non-spore-forming anaerobes. What unites both types of pathogens is that they exert pathological effects on tissues and organs under conditions of general or local hypoxia using the anaerobic metabolic pathway.

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Pathogens of anaerobic infection

By and large, pathogens of anaerobic infection include pathological processes caused by obligate anaerobes, which develop and exert their pathogenic effect under conditions of anoxia (strict anaerobes) or at low concentrations of oxygen (microaerophiles). However, there is a large group of so-called facultative anaerobes (streptococci, staphylococci, proteus, E. coli, etc.), which, when exposed to hypoxia, switch from aerobic to anaerobic metabolic pathways and are capable of causing the development of an infectious process clinically and pathomorphologically similar to a typical anaerobic one.

Anaerobes are widespread. In the human gastrointestinal tract, which is their main habitat, more than 400 species of anaerobic bacteria have been identified. The ratio of aerobes to anaerobes is 1:100.

Below is a list of the most common anaerobes whose participation in infectious pathological processes in the human body has been proven.

Microbiological classification of anaerobes

• Anaerobic gram-positive rods
  • Clostridium perfringes, sordellii, novyi, histolyticum, septicum, bifermentans, sporogenes, tertium, ramosum, butyricum, bryantii, difficile
  • Actinomyces israelii, naeslundii, odontolyticus, bovis, viscosus
  • Eubacterium limosum
  • Propionibacterium acnes
  • Bifidobacterium bifidum
  • Arachnia propionica
  • Rothia dentocariosa
• Anaerobic gram-positive cocci
  • Peptostreptococcus anaerobius, magnus, asaccharolyticus, prevotii, micros
  • Peptococcus niger
  • Ruminococcus flavefaciens
  • Coprococcus eutactus
  • Gemella haemolysans
  • Sarcina ventriculi
• Anaerobic gram-negative rods
  • Bacteroides fragilis, vulgatus, thetaiotaomicron, distasonis, uniformis, caccae, ovatus, merdae,
  • stercoris, ureolyticus, gracilis
  • Prevotella melaninogenica, intermedia, bivia, loescheii, denticola, disiens, oralis, buccalis, veroralis, oulora, corporis
  • Fusobacterium nucleatum, necrophorum, necrogenes, periodonticum
  • Porphyromonas endodontalis, gingivalis, asaccharolitica
  • Mobiluncus curtisii
  • Anaerorhabdus furcosus
  • Centipeda periodontii
  • Leptotrichia buccalis
  • Mitsuokella multiacidus
  • Tissierella praeacuta
  • Wolinella succinogenes
• Anaerobic gram-negative cocci
  • Veillonella parvula

In most pathological infectious processes (92.8-98.0% of cases), anaerobes are detected in association with aerobes, primarily with streptococci, staphylococci and bacteria of the Enterobacteriaceae family, non-fermenting gram-negative bacteria.

Among the many classifications of anaerobic infections in surgery, the most complete and responsive to the needs of clinicians is the classification proposed by A. P. Kolesov et al. (1989).

Classification of anaerobic infection in surgery

By microbial etiology:

• clostridial;
• non-clostridial (peptostreptococcal, peptococcal, bacteroid, fusobacterial, etc.).

By the nature of microflora:

• monoinfections;
• polyinfections (caused by several anaerobes);
• mixed (anaerobic-aerobic).

By affected body part:

• soft tissue infections;
• infections of internal organs;
• bone infections;
• infections of serous cavities;
• bloodstream infections.

By prevalence:

• local, limited;
• unlimited, tending to spread (regional);
• systemic or generalized.

By source of infection:

• exogenous;
• endogenous.

By origin:

• out-of-hospital;
• hospital-acquired.

By reasons of occurrence:

• traumatic;
• spontaneous;
• iatrogenic.

Most anaerobes are natural inhabitants of the skin and mucous membranes of humans. More than 90% of all anaerobic infections are endogenous. Exogenous infections include only clostridial gastroenteritis, clostridial posttraumatic cellulitis and myonecrosis, infections after human and animal bites, septic abortion and some others.

Endogenous anaerobic infection develops when opportunistic anaerobes appear in places where they are not normally found. Anaerobes penetrate tissues and the bloodstream during surgical interventions, injuries, invasive manipulations, tumor decay, and when bacteria are translocated from the intestines during acute abdominal diseases and sepsis.

However, for the development of infection, it is not enough for bacteria to simply enter unnatural places of their existence. For the introduction of anaerobic flora and the development of an infectious pathological process, additional factors are required, which include significant blood loss, local tissue ischemia, shock, starvation, stress, fatigue, etc. An important role is played by concomitant diseases (diabetes mellitus, collagenoses, malignant tumors, etc.), long-term use of hormones and cytostatics, primary and secondary immunodeficiencies against the background of HIV infection and other chronic infectious and autoimmune diseases.

One of the main factors in the development of anaerobic infections is a decrease in the partial pressure of oxygen in tissues, which occurs as a result of both general causes (shock, blood loss, etc.) and local tissue hypoxia under conditions of insufficient arterial blood flow (occlusive vascular diseases), the presence of a large number of contused, crushed, non-viable tissues.

Irrational and inadequate antibiotic therapy, aimed mainly at suppressing antagonistic aerobic flora, also contributes to the unhindered development of anaerobes.

Anaerobic bacteria have a number of properties that allow them to manifest their pathogenicity only when favorable conditions arise. Endogenous infections occur when the natural balance between the body's immune defense and virulent microorganisms is disrupted. Exogenous anaerobic infection, especially clostridial, is more pathogenic and clinically more severe than infection caused by non-spore-forming bacteria.

Anaerobes have pathogenicity factors that facilitate their invasion into tissues, reproduction and manifestation of pathogenic properties. These include enzymes, products of bacterial activity and decay, cell wall antigens, etc.

Thus, bacteroids, which mainly inhabit various parts of the gastrointestinal tract, upper respiratory tract and lower genitourinary tract, are capable of producing factors that promote their adhesion to the endothelium and damage it. Severe disorders of microcirculation are accompanied by increased vascular permeability, erythrocyte sludge, microthrombosis with the development of immune complex vasculitis, causing a progressive course of the inflammatory process and its generalization. Heparinase of anaerobes contributes to the development of vasculitis, micro- and macrothrombophlebitis. The capsule of anaerobes is a factor that sharply increases their virulence, and even brings them to the first place in associations. Secretion of neuraminidase, hyaluronidase, fibrinolysin, superoxide dismutase by bacteroids due to their cytotoxic action leads to tissue destruction and the spread of infection.

Bacteria of the genus Prevotella produce an endotoxin whose activity exceeds the action of bacteroids lipopolysaccharides, and also produce phospholipase A, which disrupts the integrity of the membranes of epithelial cells, which leads to their death.

The pathogenesis of lesions caused by bacteria of the genus Fusobacterium is due to the ability to secrete leukocidin and phospholipase A, which exhibit a cytotoxic effect and facilitate invasion.

Gram-positive anaerobic cocci normally inhabit the oral cavity, large intestine, upper respiratory tract, and vagina. Their virulent and pathogenic properties have not been sufficiently studied, despite the fact that they are often detected during the development of very severe purulent-necrotic processes of various localizations. It is possible that the pathogenicity of anaerobic cocci is due to the presence of a capsule, the action of lipopolysaccharides, hyaluronidase, and collagenase.

Clostridia are capable of causing both exogenous and endogenous anaerobic infections.

Their natural habitat is soil and the large intestine of humans and animals. The main genus-forming feature of clostridia is spore formation, which determines their resistance to unfavorable environmental factors.

In C. perfringens, the most common pathogenic microorganism, at least 12 enzyme toxins and an enterotoxin have been identified, which determine its pathogenic properties:

• alpha-Toxin (lecithinase) - exhibits dermatonecrotic, hemolytic and lethal effects.
• Beta-Toxin - causes tissue necrosis and has a lethal effect.
• Sigma-Toxin - exhibits hemolytic activity.
• theta-Toxin - has a dermatonecrotic, hemolytic and lethal effect.
• e-Toxins - cause lethal and dermatonecrotic effects.
• K-Toxin (collagenase and gelatinase) - destroys reticular muscle tissue and connective tissue collagen fibers, has a necrotic and lethal effect.
• Lambda-Toxin (proteinase) - breaks down denatured collagen and gelatin like fibrinolysin, causing necrotic properties.
• Gamma and nu-Toxins - have a lethal effect on laboratory animals.
• mu- and v-toxins (hyaluronidase and deoxyribonuclease) - increase tissue permeability.

Anaerobic infection is extremely rare as a monoinfection (less than 1% of cases). Anaerobic pathogens exhibit their pathogenicity in association with other bacteria. Symbiosis of anaerobes with each other, as well as with some types of facultative anaerobes, especially with streptococci, bacteria of the Enterobacteriaceae family, non-fermenting gram-negative bacteria, allows for the creation of synergistic associative links that facilitate their invasion and manifestation of pathogenic properties.

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How does anaerobic soft tissue infection manifest itself?

Clinical manifestations of anaerobic infection, occurring with the participation of anaerobes, are determined by the ecology of pathogens, their metabolism, pathogenicity factors, which are realized under conditions of reduced general or local immune defenses of the macroorganism.

Anaerobic infection, regardless of the localization of the focus, has a number of very characteristic clinical signs. These include:

• erasure of local classic signs of infection with a predominance of symptoms of general intoxication;
• localization of the source of infection in places where anaerobes usually live;
• an unpleasant putrid smell of exudate, which is a consequence of anaerobic oxidation of proteins;
• predominance of alterative inflammation processes over exudative ones with the development of tissue necrosis;
• gas formation with the development of emphysema and crepitation of soft tissues due to the formation of poorly water-soluble products of anaerobic metabolism of bacteria (hydrogen, nitrogen, methane, etc.);
• serous-hemorrhagic, purulent-hemorrhagic and purulent exudate with brown, gray-brown discharge and the presence of small droplets of fat in it;
• painting wounds and cavities black;
• development of infection against the background of long-term use of aminoglycosides.

If the patient has two or more of the symptoms described above, the probability of the involvement of an anaerobic infection in the pathological process is very high.

Purulent-necrotic processes occurring with the participation of anaerobes can be conditionally divided into three clinical groups:

1. The purulent process is local in nature, occurs without significant intoxication, is quickly stopped after surgical treatment or even without it, patients usually do not require intensive additional therapy.
2. The infectious process in its clinical course is practically no different from ordinary purulent processes, it proceeds favorably, like ordinary phlegmon with moderately expressed symptoms of intoxication.
3. The purulent-necrotic process proceeds rapidly, often malignantly; progresses, occupying large areas of soft tissue; severe sepsis and multiple organ failure with an unfavorable prognosis of the disease quickly develop.

Anaerobic soft tissue infections are characterized by heterogeneity and diversity both in the severity of the pathological processes they cause and in the pathomorphological changes that develop in the tissues with their participation. Various anaerobes, as well as aerobic bacteria, can cause the same type of diseases. At the same time, the same bacteria in different conditions can cause different diseases. However, despite this, several main clinical and pathomorphological forms of infectious processes involving anaerobes can be distinguished.

Various types of anaerobes can cause both superficial and deep purulent-necrotic processes with the development of serous and necrotic cellulitis, fasciitis, myositis and myonecrosis, combined lesions of several structures of soft tissues and bones.

Clostridial anaerobic infection is characterized by pronounced aggressiveness. In most cases, the disease is severe and rapid, with rapid development of sepsis. Clostridial anaerobic infection develops in patients with various types of soft tissue and bone injuries under certain conditions, which include massive contamination of tissue with soil, the presence of areas of dead and crushed tissue in the wound, deprived of blood supply, and the presence of foreign bodies. Endogenous clostridial anaerobic infection occurs in acute paraproctitis, after operations on the abdominal organs and lower extremities in patients with obliterating vascular diseases and diabetes mellitus. Less common is an anaerobic infection that develops as a result of a human or animal bite, drug injections.

Clostridial anaerobic infection occurs in two main pathomorphological forms: cellulitis and myonecrosis.

Clostridial cellulitis (crepitating cellulitis) is characterized by the development of necrosis of the subcutaneous or intermuscular tissue in the wound area. It proceeds relatively favorably. Wide, timely dissection of the wound and excision of non-viable tissues ensure recovery in most cases.

Patients with diabetes mellitus and obliterating diseases of the lower extremities have fewer chances for a favorable outcome of the disease, since the infectious process occurs in the form of cellulitis only at the first stages, then purulent-necrotic tissue damage quickly spreads to deeper structures (tendons, muscles, bones). A secondary gram-negative anaerobic infection joins in with the involvement of the entire complex of soft tissues, joints and bone structures in the purulent-necrotic process. Wet gangrene of the limb or its segment is formed, in connection with which it is often necessary to resort to amputation.

Clostridial myonecrosis (gas gangrene) is the most severe form of anaerobic infection. The incubation period lasts from several hours to 3-4 days. Severe, bursting pain in the wound occurs, which is the earliest local symptom. The condition remains unchanged. Later, progressive edema appears. The wound becomes dry, a foul-smelling discharge with gas bubbles appears. The skin acquires a bronze color. Intradermal blisters with serous-hemorrhagic exudate, foci of wet necrosis of the skin of a purple-cyanotic and brown color quickly form. Gas formation in tissues is a common sign of anaerobic infection.

In parallel with local symptoms, the general condition of the patient also worsens. Against the background of massive endotoxicosis, dysfunction processes of all organs and systems rapidly increase with the development of severe anaerobic sepsis and septic shock, from which patients die if surgical care is not provided in full on time.

A characteristic sign of infection is the defeat of the muscles by the necrotic process. They become flabby, dull, bleed poorly, do not contract, acquire a dirty brown color and have the consistency of "boiled meat". As the process progresses, the anaerobic infection quickly spreads to other muscle groups, neighboring tissues with the development of gas gangrene.

A rare cause of clostridial myonecrosis is injections of medicinal drugs. Treatment of such patients is a difficult task. Only a few patients can be saved. The case history below shows one such case.

Anaerobic streptococcal cellulitis and myositis occur as a result of various soft tissue injuries, surgeries and manipulations. They are caused by gram-positive facultative anaerobes Streptococcus spp. and anaerobic cocci (Peptostreptococcus spp., Peptococcus spp.). The disease is characterized by the development of predominantly serous cellulitis in the early stages, and necrotic cellulitis or myositis in the later stages, and occurs with symptoms of severe intoxication, often developing into septic shock. Local symptoms of infection are erased. Tissue edema and hyperemia are not pronounced, fluctuation is not determined. Gas formation occurs rarely. In necrotic cellulitis, the tissue looks faded, bleeds poorly, is gray in color, abundantly saturated with serous and serous-purulent exudate. The skin is involved in the inflammatory process secondarily: cyanotic spots with uneven edges and blisters with serous contents appear. The affected muscles look edematous, contract poorly, and are saturated with serous and serous-purulent exudate.

Due to the scarcity of local clinical signs and the prevalence of symptoms of severe endotoxicosis, surgical intervention is often performed late. Timely surgical treatment of the inflammatory focus with intensive antibacterial and detoxification therapy quickly interrupts the course of anaerobic streptococcal cellulitis or myositis.

Synergistic necrotic cellulitis is a severe, rapidly progressing purulent-necrotic disease of the cellular tissue caused by an associative non-clostridial anaerobic infection and aerobes. The disease proceeds with uncontrollable destruction of the cellular tissue and secondary involvement of adjacent tissues (skin, fascia, muscles) in the purulent-necrotic process. The skin is most often involved in the pathological process. Crimson-cyanotic confluent spots without a clear border appear, later turning into wet necrosis with ulcerations. As the disease progresses, large areas of various tissues, primarily muscles, are involved in the infectious process, and non-clostridial gangrene develops.

Necrotic fasciitis is a synergistic anaerobic-aerobic rapidly progressing purulent-necrotic process with damage to the superficial fascia of the body. In addition to anaerobic non-clostridial infection, the causative agents of the disease are often streptococci, staphylococci, enterobacteria and pseudomonas aeruginosa, usually determined in association with each other. In most cases, the underlying areas of the cellular tissue, skin, and superficial muscle layers are secondarily involved in the inflammatory process. Necrotic fasciitis usually develops after soft tissue trauma and surgical interventions. Minimal external signs of infection usually do not correspond to the severity of the patient's condition and the massive and widespread tissue destruction that is detected intraoperatively. Delayed diagnosis and late surgical intervention often lead to a fatal outcome of the disease.

Fournier's syndrome (Fournier J., 1984) is a type of anaerobic infection. It is manifested by progressive necrosis of the skin and underlying tissues of the scrotum with rapid involvement of the skin of the perineum, pubis, and penis. Often, wet anaerobic gangrene of the perineal tissues (Fournier's gangrene) develops. The disease develops spontaneously or as a result of minor trauma, acute paraproctitis, or other purulent diseases of the perineum and occurs with severe symptoms of toxemia and septic shock. It often ends in the death of patients.

In a real clinical situation, especially in the late stages of the infectious process, it can be quite difficult to differentiate the above-described clinical and morphological forms of diseases caused by anaerobes and their associations. Often, during surgical intervention, damage to several anatomical structures is detected at once in the form of necrotic fasciocellulitis or fasciomyositis. Often, the progressive nature of the disease leads to the development of non-clostridial gangrene with the involvement of the entire thickness of soft tissues in the infectious process.

The purulent-necrotic process caused by anaerobes can spread to soft tissues from the internal organs of the abdominal and pleural cavities affected by the same infection. One of the factors predisposing to this is inadequate drainage of a deep purulent focus, for example, in empyema of the pleura and peritonitis, in the development of which anaerobes participate in almost 100% of cases.

Anaerobic infection is characterized by a rapid onset. Symptoms of severe endotoxicosis (high fever, chills, tachycardia, tachypnea, loss of appetite, lethargy, etc.) usually come to the forefront, often 1-2 days ahead of the development of local signs of the disease. At the same time, some of the classic symptoms of purulent inflammation (edema, hyperemia, soreness, etc.) are lost or remain hidden, which complicates timely prehospital, and sometimes in-hospital, diagnostics of anaerobic phlegmon and delays the start of surgical treatment. It is characteristic that patients themselves often do not associate their "malaise" with the local inflammatory process until a certain time.

In a significant number of observations, especially in anaerobic necrotic fasciocellulitis or myositis, when local symptoms are dominated by only moderate hyperemia or tissue edema in the absence of fluctuation, the disease occurs under the guise of another pathology. These patients are often hospitalized with a diagnosis of erysipelas, thrombophlebitis, lymphovenous insufficiency, ileofemoral thrombosis, deep vein thrombosis of the leg, pneumonia, etc., and sometimes in non-surgical departments of the hospital. Late diagnosis of severe soft tissue infection is fatal for many patients.

How is anaerobic infection recognized?

Anaerobic soft tissue infection is differentiated from the following diseases:

• purulent-necrotic lesions of soft tissues of other infectious etiologies;
• various forms of erysipelas (erythematous-bullous, bullous-hemorrhagic);
• hematomas of soft tissues with signs of intoxication;
• vesicular dermatoses, severe toxicoderma (polymorphic exudative erythema, Stevens-Johnson syndrome, Lyell's syndrome, etc.);
• deep vein thrombosis of the lower extremities, ileofemoral thrombosis, Paget-Schroetter syndrome (subclavian vein thrombosis);
• prolonged tissue crush syndrome in the early stages of the disease (at the stage of purulent complications, the addition of anaerobic infection is determined, as a rule);
• frostbite of II-IV degree;
• gangrenous-ischemic changes in soft tissues against the background of acute and chronic thrombo-obliterating diseases of the arteries of the extremities.

Infectious emphysema of soft tissues, developing as a result of the vital activity of anaerobes, must be differentiated from emphysema of other etiologies associated with pneumothorax, pneumoperitoneum, perforation of hollow organs of the abdominal cavity into the retroperitoneal tissue, surgical interventions, washing of wounds and cavities with a solution of hydrogen peroxide, etc. In this case, in addition to crepitation of soft tissues, local and general signs of anaerobic infection are usually absent.

The intensity of the spread of the purulent-necrotic process in anaerobic infection depends on the nature of the interaction of the macro- and microorganism, on the ability of the immune defense to resist the factors of bacterial aggression. Fulminant anaerobic infection is characterized by the fact that already during the first day a widespread pathological process develops, affecting tissues over a large area and accompanied by the development of severe sepsis, uncorrectable PON and septic shock. This malignant variant of the infection leads to the death of more than 90% of patients. In the acute form of the disease, such disorders in the body develop within a few days. Subacute anaerobic infection is characterized by the fact that the relationship between the macro- and microorganism is more balanced, and with timely initiation of complex surgical treatment, the disease has a more favorable outcome.

Microbiological diagnostics of anaerobic infection is extremely important not only due to scientific interest, but also necessary for practical needs. Until now, the clinical picture of the disease has been the main method of diagnosing anaerobic infection. However, only microbiological diagnostics with identification of the infectious agent can reliably provide an answer about the participation of anaerobes in the pathological process. Meanwhile, a negative answer from a bacteriological laboratory in no way rejects the possibility of anaerobes participating in the development of the disease, since according to some data, about 50% of anaerobes are non-culturable.

Anaerobic infection is diagnosed by modern high-precision indication methods. These primarily include gas-liquid chromatography (GLC) and mass spectrometry, based on the registration and quantitative determination of metabolites and volatile fatty acids. The data from these methods correlate with the results of bacteriological diagnostics in 72%. The sensitivity of GLC is 91-97%, specificity - 60-85%.

Other promising methods for isolating anaerobic pathogens, including from blood, include the Lachema, Bactec, Isolator systems, staining preparations for detecting bacteria or their antigens in blood with acridine yellow, immunoelectrophoresis, enzyme immunoassay, and others.

An important task of clinical bacteriology at the present stage is to expand research into the species composition of pathogens with the identification of all species involved in the development of the wound process, including anaerobic infection.

It is believed that the majority of soft tissue and bone infections are of a mixed, polymicrobial nature. According to V. P. Yakovlev (1995), in extensive purulent diseases of soft tissues, obligate anaerobes are found in 50% of cases, in combination with aerobic bacteria in 48%, in a monoculture, anaerobes are detected only in 1.3%.

However, it is difficult to determine the true ratio of species composition with the participation of facultative anaerobic, aerobic and anaerobic microorganisms in practice. To a large extent, this is due to the difficulty of identifying anaerobic bacteria due to some objective and subjective reasons. The first include the capriciousness of anaerobic bacteria, their slow growth, the need for special equipment, highly nutritious media with specific additives for their cultivation, etc. The second include significant financial and time costs, the need for strict adherence to protocols for multi-stage and repeated studies, and a shortage of qualified specialists.

However, in addition to academic interest, identification of anaerobic microflora is of great clinical importance both in determining the etiology of the primary purulent-necrotic focus and sepsis, and in developing treatment tactics, including antibiotic therapy.

Below are demonstrated standard schemes for studying the microflora of a purulent focus and blood in the presence of clinical signs of anaerobic infection, used in the bacteriological laboratory of our clinic.

Each study begins with Gram staining of a smear-print from the deep tissues of the purulent focus. This study is one of the methods of express diagnostics of wound infections and can give an approximate answer about the nature of the microflora present in the purulent focus within one hour.

It is essential to use means to protect microorganisms from the toxic effects of oxygen, for which they use:

• microanaerobic aerostat for cultivating crops;
• commercial gas generator packages (GasPak or HiMedia) for creating anaerobic conditions;
• indicator of anaerobiosis: inoculation of P. aeruginosa on Simons citrate under anaerobic conditions (P. aeruginosa does not utilize citrate, and the color of the medium does not change).

Immediately after the operation, smears and biopsies from deep sections of the wound taken from one locus are delivered to the laboratory. Special transport systems of several types are used to deliver the samples.

If bacteremia is suspected, blood is cultured in parallel in 2 vials (10 ml each) with commercial media for testing for aerobic and anaerobic microorganisms.

Sowing is carried out using disposable plastic loops on several media:

1. on freshly poured Schaedler blood agar with the addition of a vitamin K + hemin complex - for cultivation in a microanaerobic jar. During primary seeding, a disk with kanamycin is used to create elective conditions (most anaerobes are naturally resistant to aminoglycosides);
2. on 5% blood agar for aerobic cultivation;
3. on enrichment medium for cultivation in a microanaerobic jar (increases the likelihood of isolating pathogens), thioglycolic or iron sulfite if a clostridial infection is suspected.

The microanaerobic jar and the dish with 5% blood agar are placed in a thermostat and incubated at +37 C for 48-72 hours. The smears delivered on glass are stained according to Gram. It is advisable to take several smears of wound discharge during the operation.

Already with microscopy in a number of cases it is possible to make a tentative conclusion about the nature of the infection, since certain types of anaerobic microorganisms have a characteristic morphology.

Obtaining a pure culture confirms the diagnosis of clostridial infection.

After 48-72 hours of incubation, colonies grown under aerobic and anaerobic conditions are compared based on their morphology and microscopy results.

Colonies grown on Schaedler agar are tested for aerotolerance (several colonies of each type). They are sown in parallel in sectors on two plates: with Schaedler agar and 5% blood agar.

Colonies grown in the corresponding sectors under aerobic and anaerobic conditions are considered indifferent to oxygen and are examined according to existing methods for facultative anaerobic bacteria.

Colonies that grow only under anaerobic conditions are considered obligate anaerobes and are identified taking into account:

• morphology and size of colonies;
• presence or absence of hemolysis;
• presence of pigment;
• ingrowth into agar;
• catalase activity;
• generic sensitivity to antibiotics;
• cell morphology;
• biochemical characteristics of the strain.

The use of commercial test systems containing more than 20 biochemical tests, which allow determining not only the genus but also the type of microorganism, significantly facilitates the identification of microorganisms.

Microscopic preparations of some types of anaerobes, isolated in pure culture, are presented below.

Detection and identification of an anaerobic pathogen from blood is possible in rare cases, such as a culture of P. niger isolated from the blood of a patient with severe wound anaerobic sepsis against the background of phlegmon of the thigh.

Sometimes, contaminants that do not play an independent etiological role in the infectious and inflammatory process may be present in the composition of microorganism associations. The isolation of such bacteria in monoculture or in associations with pathogenic microorganisms, especially when analyzing biopsy specimens from deep sections of the wound, may indicate low nonspecific resistance of the organism and, as a rule, is associated with a poor prognosis for the disease. Such results of bacteriological examination are not uncommon in severely weakened patients, in patients with diabetes mellitus, with immunodeficiency states against the background of various acute and chronic diseases.

In the presence of a purulent focus in soft tissues, bones or joints and a clinical picture of anaerobic infection (clostridial or non-clostridial), the overall frequency of isolation of anaerobes, according to our data, is 32%. The frequency of detection of obligate anaerobes in the blood in these diseases is 3.5%.

How is anaerobic infection treated?

Anaerobic infection is mainly treated by surgical intervention and complex intensive therapy. The basis of surgical treatment is radical CHO with subsequent repeated treatment of the extensive wound and its closure by available plastic methods.

The time factor in organizing surgical care plays an important, sometimes decisive, role. Delaying the operation leads to the spread of infection to larger areas, deterioration of the patient's condition and an increase in the risk of the intervention itself. The steadily progressive nature of the course of anaerobic infection is an indication for emergency or urgent surgical treatment, which should be performed after short-term preliminary preoperative preparation, consisting of the elimination of hypovolemia and gross violations of homeostasis. In patients with septic shock, surgical intervention is possible only after stabilization of arterial pressure and resolution of oliguria.

Clinical practice has shown that it is necessary to abandon the so-called "lampas" incisions without necrectomy, which were widely accepted several decades ago and are still not forgotten by some surgeons. Such tactics lead to the death of patients in almost 100% of cases.

During surgical treatment, it is necessary to perform a wide dissection of tissues affected by infection, with incisions extending to the level of visually unchanged areas. The spread of anaerobic infection is characterized by pronounced aggressiveness, overcoming various barriers in the form of fascia, aponeuroses and other structures, which is not typical for infections that occur without the dominant participation of anaerobes. Pathomorphological changes in the infection focus can be extremely heterogeneous: areas of serous inflammation alternate with foci of superficial or deep tissue necrosis. The latter can be located at significant distances from each other. In some cases, maximum pathological changes in tissues are detected far from the entry gate of infection.

In connection with the noted features of spread in anaerobic infections, a thorough revision of the inflammation focus should be carried out with wide mobilization of skin-fat and skin-fascial flaps, dissection of fascia and aponeuroses with revision of intermuscular, paravasal, paraneural tissue, muscle groups and each muscle separately. Insufficient wound revision leads to underestimation of the spread of phlegmon, volume and depth of tissue damage, which leads to insufficiently complete COGO and inevitable progression of the disease with the development of sepsis.

In CHO, it is necessary to remove all non-viable tissue regardless of the extent of the lesion. Pale cyanotic or purple skin lesions are already deprived of blood supply due to vascular thrombosis. They must be removed as a single block with the underlying fatty tissue. All affected areas of fascia, aponeuroses, muscles and intermuscular tissue must also be excised. In areas adjacent to serous cavities, large vascular and nerve trunks, joints, it is necessary to exercise a certain restraint during necrectomy.

After radical CHOGO, the edges and bottom of the wound should be visually unchanged tissue. The wound area after surgery can occupy from 5 to 40% of the body surface. There is no need to be afraid of the formation of very large wound surfaces, since only complete necrectomy is the only way to save the patient's life. Palliative surgical treatment inevitably leads to the progression of phlegmon, systemic inflammatory response syndrome and worsening of the disease prognosis.

In anaerobic streptococcal cellulitis and myositis in the serous inflammation stage, surgical intervention should be more restrained. Wide separation of skin-fat flaps, circular exposure of the group of affected muscles with separation of intermuscular tissue is sufficient to stop the process with adequate intensive detoxification and targeted antibacterial therapy. In necrotic cellulitis and myositis, surgical tactics are similar to those described above.

In clostridial myositis, depending on the extent of the lesion, a muscle, group or several muscle groups, non-viable areas of skin, subcutaneous fat and fascia are removed.

If, during revision of the surgical wound, a significant volume of tissue damage (gangrene or the possibility of the latter) is revealed with little prospect of preserving the functional capacity of the limb, then in this situation, amputation or exarticulation of the limb is indicated. Radical intervention in the form of limb truncation should also be resorted to in patients with extensive tissue damage of one or more segments of the limb in cases of severe sepsis and uncorrectable multiple myelopathy, when the prospect of preserving the limb is fraught with the loss of the patient's life, as well as in the case of a fulminant course of anaerobic infection.

Amputation of a limb in case of anaerobic infection has its own peculiarities. It is performed in a circular manner, without forming skin-muscle flaps, within healthy tissues. In order to obtain a longer limb stump, A. P. Kolesov et al. (1989) suggest performing amputation at the border of the pathological process with dissection and separation of the soft tissues of the stump. In all cases, the stump wound is not sutured, it is performed openly with loose tamponade with water-soluble ointments or iodophor solutions. The group of patients who have undergone limb amputation is the most severe. Postoperative mortality, despite the complex intensive therapy, remains high - 52%.

Anaerobic infection is characterized by prolonged inflammation with a slow change of wound process phases. The phase of wound cleansing from necrosis is sharply delayed. Development of granulation is delayed due to the polymorphism of processes occurring in soft tissues, which is associated with gross microcirculatory disorders, secondary infection of the wound. This also necessitates repeated surgical treatments of the purulent-necrotic focus (Fig. 3.66.1), which involve removal of secondary necrosis, opening of new purulent leaks and pockets, thorough wound sanitation using additional methods of exposure (ultrasonic cavitation, treatment with a pulsating stream of antiseptic, ozonation, etc.). Progression of the process with the spread of anaerobic infection to new areas serves as an indication for emergency repeated CGO. Refusal of staged necrectomy is possible only after persistent relief of the local purulent-inflammatory process and SIRS phenomena.

The immediate postoperative period in patients with severe anaerobic infection takes place in the intensive care unit, where intensive detoxification therapy, antibiotic therapy, treatment of multiple organ dysfunction, adequate pain relief, parenteral and enteral tube feeding, etc. are performed. Indications for transferring the patient to the surgical department of the hospital are positive dynamics in the course of the wound process, completion of the stage of repeated surgical treatment of the purulent focus, and sometimes plastic interventions, persistent clinical and laboratory elimination of the phenomena of PON.

Antibiotic therapy is an important link in the treatment of patients with such a disease as anaerobic infection. Given the mixed microbial etiology of the primary purulent-necrotic process, first of all, broad-spectrum drugs are prescribed, including anti-anaerobic drugs. The following combinations of drugs are most often used: cephalosporins of the II-IV generation or fluoroquinolones in combination with metronidazole, dioxidine or clindamycin, carbapenems in monotherapy.

Monitoring the dynamics of the wound process and sepsis, microbiological monitoring of discharge from wounds and other biological environments allow timely adjustments to the composition, dosage and methods of administration of antibiotics. Thus, during the treatment of severe sepsis against the background of anaerobic infection, antibacterial therapy regimens can change from 2 to 8 or more times. Indications for its cancellation are persistent relief of inflammatory phenomena in the primary and secondary purulent foci, wound healing after plastic surgery, negative blood culture results and the absence of fever for several days.

An important component of complex surgical treatment of patients with anaerobic infection is local wound treatment.

The use of a particular dressing is planned depending on the stage of the wound process, pathomorphological changes in the wound, the type of microflora, as well as its sensitivity to antibiotics and antiseptics.

In the first phase of the wound healing process, in case of anaerobic or mixed infection, the drugs of choice are hydrophilic-based ointments with anti-anaerobic action - dioxycol, streptonitol, nitacid, iodopyrone, 5% dioxidine ointments, etc. If there is gram-negative flora in the wound, both hydrophilic-based ointments and antiseptics are used - 1% iodophor solutions, 1% dioxidine solution, miramistin solutions, sodium hypochlorite, etc.

In recent years, we have widely used modern application-sorption therapy of wounds with biologically active swelling sorbents of multicomponent action on the wound process, such as lysosorb, colladiasorb, diotevin, anilodiotevin, etc. The above agents cause a pronounced anti-inflammatory, hemostatic, anti-edematous, antimicrobial effect on almost all types of bacterial flora, allow necrolysis, convert wound discharge into gel, absorb and remove toxins, decay products and microbial bodies beyond the wound. The use of biologically active draining sorbents allows early arrest of the purulent-necrotic process, inflammatory phenomena in the wound area and prepare it for plastic closure.

The formation of extensive wound surfaces resulting from surgical treatment of a widespread purulent focus creates the problem of their rapid closure by various types of plastic surgery. Plastic surgery should be performed as early as possible, as far as the condition of the wound and the patient allows. In practice, plastic surgery can be performed no earlier than the end of the second - beginning of the third week, which is due to the above-described features of the course of the wound process in anaerobic infection.

Early plastic surgery of a purulent wound is considered one of the most important elements of complex surgical treatment of anaerobic infection. The fastest possible elimination of extensive wound defects, through which massive loss of proteins and electrolytes occurs, contamination of the wound with hospital polyantibiotic-resistant flora with tissue involvement in the secondary purulent-necrotic process occurs, is a pathogenetically justified and necessary surgical measure aimed at treating sepsis and preventing its progression.

In the early stages of plastic surgery, it is necessary to use simple and least traumatic methods, which include plastic surgery with local tissues, dosed tissue stretching, ADP, and a combination of these methods. Complete (one-stage) skin plastic surgery can be performed in 77.6% of patients. In the remaining 22.4% of patients, the wound defect can only be closed in stages due to the peculiarities of the course of the wound process and its extensiveness.

The mortality rate in the group of patients who underwent a complex of plastic surgeries is almost 3.5 times lower than in the group of patients who did not undergo plastic surgery or underwent it at a later stage, 12.7% and 42.8%, respectively.

The overall postoperative mortality rate for severe anaerobic soft tissue infection, with a purulent-necrotic focus spreading over an area of more than 500 cm2 ^, is 26.7%.

Knowledge of the clinical features of the course allows a practical surgeon to identify such a life-threatening disease as anaerobic infection at early stages and plan a set of response diagnostic and therapeutic measures. Timely radical surgical treatment of an extensive purulent-necrotic focus, repeated staged necrectomy, early skin plastic surgery in combination with multicomponent intensive therapy and adequate antibacterial treatment can significantly reduce mortality and improve treatment results.