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Anthrax bacilli
First described by Polender in 1849 and later investigated by R. Koch and L. Pasteur.Morphology and physiology
Pathogen anthrax- B. anthracis - Gram-positive large rods with "chopped off" ends, located in long chains. In the external environment, they form spores that persist in the soil for many decades. In humans and animals, they form a protein capsule. R-shaped colonies are formed on solid media. It has saccharolytic and proteolytic properties, liquefies gelatin with a herringbone pattern, which is used to identify these bacteria.Antigens
B.anthracis contains two types of antigens: group-specific somatic polysaccharide and species-specific capsular antigens. The first is thermally stable, does not break down when boiled, and is stored for a long time in the external environment. This property is based on the Ascoli reaction, which has an important practical value. The capsular antigen, unlike the capsular antigens of other bacteria, is a polypeptide, not a polysaccharide. The third antigen associated with the protein toxin is called protective, since antibodies with protective properties are formed against it.Pathogenicity and pathogenesis
The virulence factors of B. anthracis primarily include a capsular polypeptide that is involved in bacterial adhesion to sensitive host cells, such as intestinal enterocytes or respiratory tract epitheliocytes. However, it has a pronounced antiphagocytic effect. Broad spectrum proteases ensure invasion. A significant role in the pathogenesis of all forms of anthrax is played by a protein toxin, which is characterized as a protective antigen, a lethal factor and an edematous factor. The production of antibodies (antitoxins) testifies to the protective activity. Lethal and edematous factors according to the mechanism of action can be attributed to cytotoxins and functional blockers. Depending on the entrance gate of infection, there are skin, pulmonary and intestinal forms of anthrax. In the cutaneous form, the pathogen penetrates into the deep layers of the dermis at the border of the subcutaneous tissue, causing the formation of a specific carbuncle - a focus of hemorrhagic-necrotic inflammation. The causative agent from the site of introduction is brought by macrophages to the regional lymph nodes, in which inflammation develops. In the cutaneous form, septicemia develops in 1-2% of cases and much more often in other forms due to the generalization of the process.Immunity
After the transfer of anthrax, intense humoral antitoxic immunity is formed, in which antibodies play a significant role - antitoxins to the protective antigen - protein toxin. Of particular importance in immunity is T-dependent allergy, manifested in HRT.Ecology and epidemiology
Anthrax is an acute, especially dangerous infection mainly of farm animals and people. According to some scientists, the natural habitat for anthrax bacilli is the soil, in which the pathogen multiplies and persists for a long time in the form of spores. Soil infection occurs through the excretion of sick animals and the burial of their corpses. Others believe that the soil is only a repository for spores. The pathogen is transmitted to people through products prepared from infected material, especially meat when caring for sick animals, processing animal raw materials. In some cases, infection occurs through blood-sucking insects - gadflies, flies, zhigalok, by aerosol (disease of junk workers), as well as through contact with skins and skin from sick animals. Laboratory diagnostics. The most reliable is a bacteriological study, ending with the isolation of a pure culture of the pathogen and its identification using the "pearl necklace" test, which appears on nutrient agar with penicillin due to the transformation of bacteria into protoplasts. To identify the contamination of raw materials (fur skins, leather, etc.), the Ascoli thermoprecipitation reaction is used. To identify infected animals, a skin-allergic test is used.Anthrax (malignant carbuncle)
Anthrax is an acute, especially dangerous infectious disease of domestic and wild animals, from which humans are also infected through direct contact with sick animals and various raw materials. There are skin, pulmonary and intestinal forms of the disease. The causative agent of anthrax - Bacillus anthracis - belongs to the genus Bacillus of the Bacillaceae family. The genus Bacillus combines several more species of bacilli, with which it is necessary to differentiate isolated cultures of anthrax. The main ones are B.cereus, B. anthracoides, B. subtilis, B. megaterium.Taking material and sending samples
When conducting laboratory diagnosis of anthrax in humans, various materials are examined depending on the clinical form of the disease: in the skin form - the contents of vesicles, carbuncles, in the intestinal - stool; pulmonary - sputum. Blood is examined in all clinical forms. Blood is taken from the corpse, pieces of parenchymal organs. If it is impossible to immediately inoculate material from a corpse, blood, bone marrow and spleen punctates are prepared on glass slides and dried. All samples are placed in glass jars, vials, test tubes. Dried smears are placed in Petri dishes, wrapped with waxed or parchment paper, the package is labeled "Caution, smears are not fixed!" All selected material is carefully placed in a metal or wooden box, sealed or sealed with sealing wax, on the lid they write "Top, carefully!" An accompanying document is drawn up, which indicates what material, place and time of sampling, from whom it was taken, and immediately sent by courier to a special (security) laboratory. An autopsy of animals that died from anthrax is not carried out, since this contributes to sporulation and dispersion of the pathogen. If necessary, it is allowed to take only the ear, it is placed in a jar, and the incision site is cauterized with a blowtorch or concentrated solution carbolic acid. They also take samples of skins, wool, wool, bristles. In some cases, food products (meat), water, soil are examined. Laboratory diagnosis of anthrax consists of several stages: bacterioscopy of smears, isolation and identification of a pure culture of the pathogen, bioassay, Ascoli's thermokilse precipitation reaction, and allergic test.Bacterioscopic method
From the blood, the contents of the vesicles, sputum, 4 smears are made from each sample, they are stained according to Gram, Romanovsky-Giemsa, anthrax luminescent serum, Rebiger's solution, which simultaneously fixes and stains the preparation. From different ways Rebiger's method for detecting capsules is simple and demonstrative. Take 15-20 g of violet gentian and dissolve in 100 ml of 40% formalin. The solution is kept at room temperature for several hours, then filtered. An unfixed smear is stained for 15-20 seconds, washed, dried. The body of the bacilli turns dark purple, and the capsules turn red-violet, according to Romanovsky-Giemsa, the cell body becomes bluish, and the capsule becomes light pink. When a smear is processed with fluorescent serum, anthrax bacilli under a fluorescent microscope look like large sticks surrounded by a bright greenish rim. The presence in smears of typical bacilli, which are arranged in chains surrounded by capsules, give a specific fluorescence, makes it possible to make a preliminary diagnosis of anthrax.Bacteriological and biological research
The final diagnosis of anthrax can only be made after the isolation of a pure culture and a positive bioassay on animals. The test material is sown in the BCH, plates with MPA and blood agar. Crops are incubated at a temperature of 37 ° C for 18-20 hours. Simultaneously with the inoculation of emulsified research material, laboratory animals are subcutaneously infected. It is administered to white mice at the root of the tail - 0.1 ml, to guinea pigs under the skin of the abdomen - 0.2 ml, to rabbits - 0.5-3.0 ml. microbes in the form of long chains (streptobacilli). Large rough matte R-shaped colonies with an uneven, fibrous, curly edge ("jellyfish head", "lion's mane") grow on the surface of the MPA. Such colonies must be studied under a low magnification microscope in transmitted light. On blood agar, the colonies have an S- or SM-shape without hemolysis, while a large zone of medium enlightenment appears around the colonies of anthracoids. On MPA and MPB, B. anthracis grows without the formation of capsules under normal aerobic conditions, which does not allow one to determine one of the most important its signs. To detect capsule formation, the best ways are to infect white mice, followed by staining smears-imprints from organs and inoculation on a special elective agar of Buza (Hungary) and Tom (Bulgaria) or on a medium containing Hanks' solution and 40% sterile bovine serum. Crops are grown in an atmosphere of 20-40% CO2. The next day, after microscopy, 2-3 suspicious colonies are sifted out on a slanted MPA to isolate a pure culture. Animals die after 24-36 hours from acute septicemia, they are autopsied, blood and spleen cultures are made and swabs are examined as described above. On On the 3rd day of the study, white mice are infected, but already with a pure culture, additional crops are carried out and tests are performed for its final identification and differentiation from anthracoids and some soil bacilli. In this case, the main and additional features are taken into account. The main criteria include specific pathogenicity, capsule formation, the "pearl necklace" test on a medium with penicillin, lysis with a specific phage, and a luminescent serological test. Additional features are lecithinase activity, lack of mobility and hemolysis. Specific pathogenicity is determined by introducing 0.2 ml of a culture suspension to white mice. The detection of large sticks surrounded by a capsule in smears-imprints from the organs of dead animals indicates the presence of specific pathogenicity in microbes. When mice are infected with too high doses of cultures of soil bacilli, the animals sometimes get sick, but the phenomenon of capsule formation is absent. The "pearl necklace" test is carried out as follows. Penicillin is added to Hottinger's broth with horse serum (30%) in the amount of 0.5 IU / ml and 2 drops of a young isolated culture are sown. After 3 hours of growth in a thermostat, smears are made, stained with methylene blue and microscoped. Siberian bacilli are arranged in chains of spherical shapes, resembling pearl beads. Saprophytic pound bacilli, insensitive to penicillin, grow as usual, and rod-shaped chains are found in smears. watch culture. The cup is dried again for 30 minutes and then a small drop of a specific anthrax bacteriophage is applied to the center of each culture plaque with a loop with a diameter of 2 mm. The results are recorded after 5-6 hours of incubation at 37 ° C. If the culture belongs to B. athracis, lysis in the form of a sterile spot is visible at the site of application of the phage. No species of saprophytic bacilli is insensitive to the action of a specific phage. An isolated culture can be quickly identified using diagnostic anthrax serum labeled with fluorescein (rhodamine). A smear from the capsule culture is fixed with methanol, then treated with luminescent serum for 20 minutes, washed buffer solution , dried and microscopically under a fluorescent microscope. In smears around cells with a capsule, a specific glow is observed in the form of bright green rims. Now, the indirect variant of RIF is more often used. The absence of mobility is detected by the method of pressured (hanging) drops or by inoculation injection into a test tube with semi-liquid agar, and the absence of hemolysis is determined after inoculation on blood agar. Tests for lecithinase and phosphatase are carried out using conventional methods. Thus, large gram-positive immobile rods with capsules, growing in the form of characteristic R-forms of colonies, highly pathogenic for experimental animals, give the "pearl necklace" test, glow brightly when anthrax is treated with luminescent serum, identify as B. anthracis. In cases where it is very difficult or even impossible to isolate the pathogen from the test material (animal corpses, skin, fur, wool, wool), as well as in the control of animal raw materials in some industries, a very sensitive and specific reaction is widely used thermokiltseprecipitation Ascoli. It makes it possible to detect even a small amount of anthrax bacillus antigen in the material. First, the material is crushed, then poured with a 10-fold volume of 0.85% sodium chloride solution, boiled for 10-15 minutes, filtered through asbestos wool. In some cases, the material is poured with a triple volume of 0.5% acetic acid solution. In this case, a more complete extraction of the antigen occurs. The "cold" method is more often used for mass examination of leather and other raw materials. Samples of the material are sterilized in an autoclave, crushed, filled with a 10-fold volume of isotonic solution and left at a temperature of 6-16 ° C for 20-24 hours, filtered in the same way. In all cases, the antigen should be as transparent as possible. The second component of the reaction - precipitating serum - is obtained by hyperimmunization of horses with the STI vaccine or a killed culture of B. anthracis. 3 ml thermoextract. At the border of two liquids, a thin ring of whitish precipitate is formed in 2-5 minutes (turbidity of the liquid). The appearance of a precipitate after 10 minutes is considered a non-specific reaction. In parallel put several controls: precipitating serum + positive extract; precipitating serum + extract from non-Siberian material; precipitating serum + isotonic solution; normal serum + thermoetract, etc. . The first control should always be positive, all others negative.Serological diagnosis
Serological diagnosis of anthrax is rarely carried out, mainly in cases where the causative agent of the disease cannot be isolated. To detect antibodies in the blood serum of patients, highly sensitive methods such as RNHA, ELISA, coagglutination reaction with protective anthrax antigen are used.Allergic method
The body of patients and those who have been ill with anthrax in humans, as well as after vaccination, reacts with a local allergic reaction to the intradermal administration of the allergen. The state of sensitization occurs already on the 4-5th day of illness and persists for a very long time. Anthraxin, a protein-polysaccharide complex obtained by hydrolysis of vegetative forms of anthrax bacilli, serves as an allergen for setting the sample. The drug is administered intradermally on the palmar surface of the forearm in a volume of 0.1 ml. The result is taken into account after 24 and 48 hours. The sample is considered positive if hyperemia and infiltration with a diameter of more than 15 mm occur.Prevention and treatment
For the specific prevention of anthrax, a live vaccine obtained by domestic scientists is used. Specific anti-anthrax immunoglobulin is used for late prevention and treatment of this disease. Of the antibiotics, beta-lactams, aminoglycosides, tetracyclines and other drugs are used.anthrax (malignant carbuncle) - acute infectious disease zoonotic origin, occurring mainly in the form of a skin form, rarely observed pulmonary and intestinal forms, introduced into the group of especially dangerous infections.
anthrax in a susceptible organism, the vegetative form forms a capsule; in the environment, with access to free air oxygen and a temperature of 15-42 ° C, a spore located in the center of the rod is formed from vegetative cells. The pathogenicity of the microbe is determined by the capsule (which has antiphagocytic activity and promotes fixation of the microbe on the host cells) and a thermolabile exotoxin, consisting of three components - edematous (edematous), protective antigen (immunogen) and a lethal factor.
Anthrax. Etiology.
The causative agent is a gram-positive immobile large bacillus Bacillus anihracis 6-10 µm long and 1-2 µm wide, Gram-stained, forms spores and a capsule, is an aerobe and an facultative anaerobe. Grows well on various nutrient media. In a susceptible organism, the vegetative form of the pathogen forms a capsule; in the environment, with access to free air oxygen and a temperature of 15-42 ° C, a spore located in the center of the rod is formed from vegetative cells. Vegetative forms quickly die without air access, when heated, under the influence of various disinfectants. The virulence of the pathogen is due to the presence of a capsule and exotoxin. In addition to penicillin, the causative agent of anthrax is also sensitive to antibiotics of the tetracycline group, chloramphenicol, streptomycin, neomycin.
anthrax has various pathogenicity factors. Pathogenicity is determined by the capsule (which has antiphagocytic activity and promotes fixation of the microbe on host cells) and a thermolabile exotoxin, consisting of three components - edematous (edematous), protective antigen (immunogen) and a lethal factor.
Anthrax. resistance.
anthrax in the vegetative form, it is relatively little stable: at a temperature of 55 ° C they die after 40 minutes, at 60 ° C - after 15 minutes, when boiled - instantly. Vegetative forms are inactivated with standard disinfectant solutions after a few minutes. In unopened corpses, they persist for up to 7 days.
anthrax has spores that are very stable in the external environment, they can persist in the soil for up to 10 years or more, are formed outside the body with the access of free oxygen. The spores are extremely resistant: after 5-10 minutes of boiling, they all retain the ability to grow. Under the action of dry heat at 120-140°C, they die after 1-3 hours, in an autoclave at 110°C - after 40 minutes. 1% formalin solution and 10% sodium hydroxide solution kill spores in 2 hours. The duration of spore survival is affected by the ambient temperature at which sporulation occurred. Spores formed at a temperature of 18-20°C are more stable.
Anthrax. Epidemiology.
anthrax has various sources of infection, for example, domestic animals (cattle, sheep, goats, camels, pigs). Infection can occur when caring for sick animals, slaughtering livestock, processing meat, as well as in contact with animal products (skins, skins, furs, wool, bristles) contaminated with anthrax spores. The infection is predominantly professional in nature. Infection can occur through soil in which anthrax spores persist for many years. Spores enter the skin through microtrauma; with alimentary infection (consumption of contaminated products), an intestinal form occurs.
Among animals, the alimentary route of infection is of great epizootological importance - through food, water contaminated with anthrax spores, aerosol, transmissible infection routes, through milk and dairy products, are of less importance. Carriers of the pathogen can be horseflies and flies, in the mouth apparatus of which the pathogen can persist for up to 5 days.
anthrax can be transmitted by air (inhalation of infected dust, bone meal). In these cases anthrax initiates pulmonary and generalized forms of infection. In African countries, the possibility of transmission of infection through the bites of blood-sucking insects is allowed. Human-to-human transmission is usually not observed. anthrax widespread in many countries of Asia, Africa and South America. In the USA and European countries anthrax is extremely rare and isolated cases of diseases are observed.
Anthrax. Pathogenesis.
The absence of infection of a person from a person is explained by the peculiarities of the transmission mechanism implemented among animals or from an animal to a person and impossible among people by the peculiarities of the first phase of the isolation of the pathogen from an infected organism. In a sick animal, before death, the pathogen is excreted with various excretions, the blood from the corpse is saturated with anthrax bacilli, which leads to a high intensity of infection of animal products. Spontaneous release of anthrax rods from the skin lesion in humans is not observed. Since no rods are found in the serous-hemorrhagic exudate of the carbuncle at the onset of the disease, instrumental intervention is required to isolate them from the blood. Anthrax rods are also absent in the discharge of a patient with a septic form of the disease.
anthrax mostly penetrates through the skin. Usually, the pathogen is introduced into the skin of the upper limbs (about half of all cases) and the head (20-30%), less often the trunk (3-8%) and legs (1-2%). Mostly exposed areas of the skin are affected. Within a few hours after infection, the pathogen begins to multiply at the site of the infection gate (in the skin). In this case, pathogens form capsules and secrete exotoxin, which causes dense swelling and necrosis.
Capsule, which is a polypeptide, has antiphagocytic activity, prevents opsonization and phagocytosis of bacilli and at the same time promotes their fixation on host cells. anthrax due to this, it becomes invasive and can take root in the macroorganism, then it multiplies and develops bacteremia. anthrax has strains that have a capsule, but it distinguishes virulent strains of anthrax from vaccine.
exotoxin inhibits nonspecific bactericidal activity of humoral and cellular factors, phagocytosis, has anticomplementary activity, increases the virulence of anthrax bacilli, causes death in the terminal stage of the disease, inhibiting the function of the respiratory center and hypothalamus. Endogenous products of anthrax microbes do not have a pronounced toxic effect.
From the places of primary reproduction, pathogens reach the regional lymph nodes through the lymphatic vessels, and further hematogenous spread of microbes to various organs is possible. In the skin form at the site of the primary inflammatory-necrotic focus, secondary bacterial infection does not play a special role.
During aerogenic infection, spores are phagocytosed by alveolar macrophages, then they enter the mediastinal lymph nodes, where the pathogen multiplies and accumulates, the mediastinal lymph nodes are also necrotized, which leads to hemorrhagic mediastinitis and bacteremia. As a result of bacteremia, secondary hemorrhagic anthrax pneumonia occurs.
When eating infected (and insufficiently heated) meat, spores penetrate the submucosa and regional lymph nodes. The intestinal form of anthrax develops, in which pathogens also penetrate into the blood and the disease passes into a septic form. Thus, anthrax may have a septic course with any form of infection. In the pathogenesis of anthrax, exposure to toxins produced by the pathogen is of great importance.
Anthrax. Immunity.
The transferred disease leaves behind stable immunity, although there are descriptions of repeated diseases 10-20 years after the first disease.
Anthrax. Symptoms and course.
anthrax It has an incubation period that ranges from a few hours to 8 days (usually 2-3 days). anthrax It has various forms, distinguish skin, pulmonary (inhalation) and intestinal. The last two forms are characterized by hematogenous dissemination of microorganisms and are sometimes combined under the name of a generalized (septic) form, although these two forms differ in changes in the infection gate area. The skin form is most often observed (in 95%), rarely pulmonary and very rarely (less than 1%) intestinal.
Skin form subdivided into the following clinical varieties: carbuncle, edematous, bullous and erysipeloid [Nikiforov VN, 1973]. The most common is the carbuncle variety. The cutaneous form is characterized by local changes in the area of the infection gate. At the beginning, a red spot appears at the site of the lesion, which rises above the level of the skin, forming a papule, then a vesicle develops at the site of the papule, after a while the vesicle turns into a pustule, and then into an ulcer. The process proceeds quickly, from the moment the spot appears to the formation of a pustule, several hours pass.
Locally, patients report itching and burning. The contents of the pustule often have a dark color due to the admixture of blood. If the integrity of the pustule is violated (more often with scratching), an ulcer is formed, which is covered with a dark crust. Around the central scab, secondary pustules are located in the form of a necklace, with the destruction of which the size of the ulcer increases. Around the ulcer, there is swelling and hyperemia of the skin, especially pronounced when the process is localized on the face. Characterized by a decrease or complete absence of sensitivity in the area of the ulcer.
Most often, the ulcer is localized on the upper extremities: fingers, hand, forearm, shoulder (498 cases out of 1329), followed by the forehead, temples, crown, cheekbone, cheek, eyelid, lower jaw, chin (486 patients), neck and occiput (193 ), chest, collarbone, mammary glands, back, abdomen (67), on the lower extremities the ulcer was localized only in 29 people. Other localizations were rare.
Signs of general intoxication (fever up to 40 ° C, general weakness, fatigue, headache, weakness, tachycardia) appear by the end of the first day or on the 2nd day of illness. The fever lasts for 5-7 days, the body temperature drops critically. Local changes in the area of the ulcer gradually heal, and by the end of the 2-3rd week the scab is torn off. Usually there is a single ulcer, although sometimes there may be multiple (2-5 and even 36). An increase in the number of ulcers does not have a noticeable effect on the severity of the course of the disease. The age of the patient has a greater influence on the severity of the course of the disease. Before the introduction of antibiotics, mortality among patients older than 50 years was 5 times higher (54%) than among younger patients (8-11%). In those vaccinated against anthrax, skin changes may be very slight, resembling a common boil, and general signs of intoxication may be absent.
The edematous variety of the cutaneous form of anthrax is rare and is characterized by the development of edema without a visible carbuncle at the onset of the disease. The disease is more severe with severe manifestations of general intoxication. Later, in place of dense painless edema, skin necrosis appears, which is covered with a scab.
anthrax has a bullous variety of the skin form, which is rarely observed. It is characterized by the fact that in place of a typical carbuncle in the area of the gate of infection, blisters filled with hemorrhagic fluid form. They appear on the inflamed infiltrated base. Bubbles reach large sizes and open only on the 5-10th day of illness. In their place, an extensive necrotic (ulcerative) surface is formed. This type of anthrax occurs with high fever and severe symptoms of general intoxication.
anthrax has an erysipeloid variety of the skin form, which is most rarely observed. Its specialty is education. a large number whitish blisters filled with a clear liquid, located on swollen, reddened, but painless skin. After opening the blisters, multiple ulcers remain, which quickly dry out. This variety is characterized by a milder course and a favorable outcome.
Pulmonary form anthrax begins acutely, proceeds severely, and even with modern methods treatment can be fatal. Among full health, a stunning chill occurs, body temperature quickly reaches high numbers (40 ° C and above), conjunctivitis is noted (lacrimation, photophobia, conjunctival hyperemia), catarrhal phenomena from the upper respiratory tract (sneezing, runny nose, hoarse voice, cough). The condition of patients from the first hours of the disease becomes severe, there are severe stabbing pains in the chest, shortness of breath, cyanosis, tachycardia (up to 120-140 beats / min), blood pressure decreases. There is an admixture of blood in the sputum. Above the lungs, areas of dullness of percussion sound, dry and wet rales, and sometimes pleural friction noise are determined. Death occurs in 2-3 days.
intestinal form Anthrax is characterized by general intoxication, fever, epigastric pain, diarrhea and vomiting. In the vomit and in the feces there may be an admixture of blood. The abdomen is swollen, sharply painful on palpation, signs of peritoneal irritation are revealed. The patient's condition progressively worsens and with the phenomena of infectious-toxic shock, patients die.
With any of the described forms, anthrax sepsis with bacteremia, the occurrence of secondary foci (meningitis, damage to the liver, kidneys, spleen, and others) can develop.
Anthrax. Diagnosis and differential diagnosis.
anthrax is recognized on the basis of epidemiological history data (the profession of the patient, the nature of the processed material, where the raw materials were delivered from, contact with sick animals, etc.). Characteristic changes in the skin in the area of the infection gate are also taken into account (location in open areas of the skin, the presence of a dark scab surrounded by secondary pustules, edema and hyperemia, anesthesia of the ulcer). It should be borne in mind that in vaccinated all skin changes can be mild and resemble staphylococcal diseases (furuncle and others).
anthrax is confirmed by laboratory methods and is produced through the isolation of an anthrax culture and its identification. For research, the contents of the pustule, vesicles, tissue effusion from under the scab are taken. If a pulmonary form is suspected, blood, sputum, and feces are taken. In cutaneous forms, blood culture is rarely isolated. Taking and sending the material is carried out in compliance with all the rules for working with especially dangerous infections.
To study the material (skins, wool), a thermoprecipitation reaction is used (Accol reaction). An immunofluorescent method is also used to detect the pathogen. As helper method you can use a skin-allergic test with a specific allergen - anthraxin. The drug is administered intradermally (0.1 ml). The result is taken into account after 24 and 48 hours. A reaction is considered positive if there is hyperemia and an infiltrate over 10 mm in diameter, provided that the reaction has not disappeared after 48 hours.
It is necessary to differentiate from the furuncle, carbuncle, erysipelas, in particular from the bullous form. The pulmonary (inhalation) form of anthrax is differentiated from the pulmonary form of plague, tularemia, melioidosis, legionellosis and severe pneumonia of another etiology.
Anthrax. Treatment.
anthrax it is rather difficult to treat, antibiotics are used for etiotropic treatment, as well as specific immunoglobulin. Most often, penicillin is prescribed for the cutaneous form of 2 million-4 million IU / day parenterally. After the disappearance of edema in the ulcer area, penicillin preparations can be administered orally (ampicillin, oxacillin for another 7-10 days).
In pulmonary and septic forms, penicillin is administered intravenously at a dose of 16-20 million units / day, with anthrax meningitis, such doses of penicillin are combined with 300-400 mg of hydrocortisone. In case of intolerance to penicillin in the skin form of anthrax, tetracycline is prescribed at a dose of 0.5 g 4 times a day for 7-10 days. You can also use erythromycin (0.5 g 4 times a day for 7-10 days). Recently, ciprofloxacin 400 mg every 8-12 hours has been recommended, as well as doxycycline 200 mg 4 times a day, and then 100 mg 4 times a day.
Specific anti-anthrax immunoglobulin is administered intramuscularly at a dose of 20-80 ml/day (depending on the clinical form and severity of the disease) after preliminary desensitization. First, to test the sensitivity to horse protein, 0.1 ml of immunoglobulin, diluted 100 times, is injected intradermally. In case of a negative test, 0.1 ml of diluted (1:10) immunoglobulin is injected subcutaneously after 20 minutes and the entire dose intramuscularly after 1 hour. With a positive intradermal reaction, it is better to refrain from administering immunoglobulin.
Anthrax. Forecast.
Before the introduction of antibiotics, mortality in the cutaneous form reached 20%, with modern early antibiotic treatment, it does not exceed 1%. With pulmonary, intestinal and septic forms, the prognosis is unfavorable.
Anthrax. Prevention, control measures and measures in the outbreak.
Veterinary activities are:
1. Identification, registration, certification of points unfavorable for anthrax.
2. Scheduled immunization of farm animals in disadvantaged areas.
3. Control over the implementation of reclamation and agrotechnical measures aimed at improving the unfavorable territories and water bodies.
4. Control over the proper condition of cattle burial grounds, cattle driving routes, pastures, livestock facilities.
5. Monitoring compliance with veterinary and sanitary rules during the procurement, storage and transportation and processing of raw materials.
6. Timely diagnosis of anthrax in animals, their isolation and treatment.
7. Epizootological examination of the epizootic focus, neutralization of the corpses of dead animals, current and final disinfection in the focus.
8. Veterinary and sanitary educational work among the population.
9. Preventive measures against anthrax include public health and veterinary measures.
Health measures are:
1. Control over the implementation of general sanitary preventive measures in areas unfavorable for anthrax, during the procurement, storage, transportation and processing of raw materials of animal origin.
2. Vaccination of persons at increased risk of anthrax infection (according to indications).
3. Timely diagnosis of anthrax disease in people, hospitalization and treatment of patients, epidemiological examination of the focus and final disinfection in the room where the sick person was.
4. Emergency prophylaxis among persons in contact with the source of the infectious agent or with infected products.
5. Sanitary and educational work among the population.
Anthrax. Vaccination.
Persons who work with live cultures of the pathogen, infected laboratory animals, examine material infected with the anthrax pathogen, veterinarians and other persons professionally engaged in pre-slaughter keeping of livestock, slaughter, butchering carcasses and skinning, as well as those engaged in the collection, storage, transportation and primary processing of raw materials of animal origin. Vaccination is carried out with live STI anthrax vaccine twice with an interval of 21 days. Revaccination is carried out annually with an interval of no more than a year in order to be in time before the seasonal rise in the incidence.
Anthrax. Laboratory diagnostics.
Laboratory diagnosis is based on a bacteriological examination of the contents of skin lesions, and if a generalized form is suspected, on a study of blood, sputum, and feces (early use of antibiotics sharply reduces the pathogen's seeding). They put a skin-allergic test with anthraxin, which in the first week of the disease is positive in 90% of cases. A positive test result is not taken into account in persons previously vaccinated against anthrax, if the period from the moment of vaccination does not exceed 12 months. Laboratory studies are carried out in compliance with the regime that is mandatory when working with pathogens of especially dangerous infections.
Bacillus anthracis immobile, gram-positive (gram-negative cells are also found in young and old cultures), forming a capsule (in the body or when cultivated on artificial nutrient media with a high content of native protein and CO2) and a spore rod, 1-1.3 x 3.0- 10.0 µm. At temperatures below 12 and above 42 ° C, as well as in a living organism or an unopened corpse, spores are not formed in the blood and serum of animals. In stained preparations from the blood and tissues of animals sick or dead from anthrax, bacteria are located singly, in pairs and in the form of short chains of 3-4 cells; the ends of the sticks facing each other are straight, sharply chopped off, free - slightly rounded. Sometimes the chains are shaped like a bamboo cane. In smears from cultures on solid and liquid nutrient media, the sticks are arranged in long chains.
Cultivation.
Bacillus anthracis according to the method of respiration, they are classified as facultative anaerobes; they grow well on universal media (MPB, MPA, MPZH, potatoes, milk). The optimal growth temperature on MPA is 35-37 o C, in broth 32-33 o C. 45 o C does not grow. The optimum pH of the media is 7.2-7.6. On the surface of MPA under aerobic conditions at a temperature of 37 o C 17-24-hour cultures consist of grayish-whitish fine-grained with a silvery tint, similar to snowflakes, colonies with a rough relief and characteristic of typical virulent strains (R-form). The diameter of the colonies does not exceed 3-5 mm. On serum agar and clotted horse serum in the presence of 10-50% carbon dioxide, the colonies are smooth, translucent (S-form), and also mucous (mucoid), stretching for a loop (M-form), consisting of capsule sticks. In MPB Bacillus anthracis after 16-24 hours at the bottom of the tube forms a loose white precipitate, 
the supernatant remains transparent, the broth does not become cloudy when shaken, the precipitate breaks into small flakes (R-form). When sown in a column of gelatin, a yellowish-white rod appears on the 2-5th day. The culture resembles a Christmas tree turned upside down. Gradually, the top layer of gelatin begins to liquefy, first taking the form of a funnel, then a bag. Bacillus anthracis when growing in milk, it produces acid and, after 2-4 days, coagulates it and peptonizes the clot. The pathogen multiplies well in 8-12-day-old chicken embryos, causing their death for 2-4 days from the moment of infection.
biochemical properties.
Enzymes Bacillus anthracis: lipase, diastase, protease, gelatinase, dehydrase, cytochrome oxidase, peroxidase, catalase, lecithinase, etc. It ferments glucose, maltose, sucrose, trehalose, fructose and dextrin with the formation of acid without gas. On media with glycerol and salicin, weak acid formation is possible. Arabinose, rhamnose, galactose, mannose, raffinose, inulin, mannitol, dulcitol, sorbitol, inositol does not ferment. Utilizes citrates, forms acetylmethylcarbinol (Voges-Proskauer reaction is positive). Releases ammonia. Reduces methylene blue and restores nitrate to nitrite. Some strains produce hydrogen sulfide.
Toxin formation.
Bacillus anthracis forms a complex exotoxin consisting of three components: edematogenous factor (EF), protective antigen (RA) and lethal factor (LF) or factors I, II, III. The edematogenous factor causes a local inflammatory reaction - swelling and tissue destruction. Protective antigen - carrier of protective properties, has a pronounced immunogenic effect. A lethal factor mixed with a protective one causes the death of rats, white mice and guinea pigs. Each of the three factors has a pronounced antigenic function and is serologically active. The invasive properties of the microbe are due to the capsular polypeptide of d-glutamic acid and exoenzymes.
Antigenic structure.
The composition of antigens Bacillus anthracis includes a non-immunogenic somatic polysaccharide complex and a capsular glutamine polypeptide. The polysaccharide antigen does not create immunity in animals and does not determine the aggressive functions of the microorganism.
Sustainability.
In an unopened corpse, the vegetative cell of the microbe is destroyed within 2-3 days, in buried corpses it will remain for up to 4 days. In frozen meat at minus 15 o C it is viable for 15 days, in salted meat - up to 1.5 months. In slurry mixed with anthrax blood, it dies after 2-3 hours, while spores remain virulent in it for months. In sealed ampoules with broth cultures, they can remain viable and virulent up to 63 years, in the soil - more than 50 years. Alcohol, ether, 2% formalin, 5% phenol, 5-10% chloramine, fresh 5% - bleach solution, hydrogen peroxide destroy vegetative cells within 5 minutes. Ethanol 25-100% kills spores for 50 days or more, 5% phenol, 5-10% chloramine solution - from several hours to several days, 2% formalin solution - after 10-15 minutes, 3% hydrogen peroxide solution - after 1 hour, 4% potassium permanganate solution - after 15 minutes, 10% sodium hydroxide solution - after 2 hours. Vegetative cells die within 1 hour when heated to 50-55 o C, at 60 o C - after 15 minutes, at 75 o C - after 1 minute, when boiling - instantly. With slow drying, sporulation occurs and the microbe does not die. At minus 10 o C, bacteria persist for 24 days, at minus 24 o C - 12 days. Exposure to direct sunlight neutralizes bacteria after a few hours. Dry heat at a temperature of 120-140 o C kills spores after 2-3 hours, at 150 o C - after 1 hour, flowing steam at 100 o C - after 12-15 minutes, autoclaving at 110 o C - for 5-10 minutes, boiling - after 1 hour. Anthrax is highly sensitive to penicillin, chlortetracycline and chloramphenicol, and also to lysozyme. Freshly milked cows' milk has a bacteriostatic effect for 24 hours.
Pathogenicity.
All species of mammals are susceptible to the anthrax pathogen. Sheep, cattle, horses, goats, buffaloes, camels, and reindeer are more commonly affected; donkeys and mules may be infected. Pigs are less sensitive. Among wild animals, all herbivores are susceptible. There are known cases of disease in dogs, wolves, foxes, arctic foxes, among birds - ducks and ostriches.
Pathogenesis.
Infection of animals occurs mainly alimentary. Through the damaged mucosa of the digestive tract, the microbe penetrates into the lymphatic system, and then into the blood, where it phagocytizes and spreads throughout the body, fixing in the elements of the lymphoid-macrophage system, after which it migrates back into the blood, causing septicemia. The capsule substance inhibits opsonization, while how exotoxin destroys phagocytes, affects the central nervous system, causes edema, hyperglycemia occurs and alkaline phosphatase activity increases. In the terminal phase of the process, the oxygen content in the blood decreases to a level incompatible with life.
Laboratory diagnostics.
For laboratory research, the ear of a fallen animal is sent to anthrax.
Bacterioscopy. Smears are prepared from the pathological material for microscopy, some are stained according to Gram and always on capsules according to Mikhin and Olt. The detection of capsular rods typical in morphology is an important diagnostic sign. Sowing on nutrient media. The starting material is inoculated in the BCH and on the MPA (pH 7.2-7.6), the inoculations are incubated at a temperature of 37 o C for 18-24 hours, in the absence of growth they are kept in a thermostat for another 2 days. Biological sample. It is carried out on white mice, guinea pigs, rabbits, simultaneously with the inoculation of the material on nutrient media. White mice are infected subcutaneously in the back of the back (0.1-0.2 ml each), guinea pigs and rabbits - under the skin in the abdomen (0.5-1.0 ml each). Mice die in 1-2 days, guinea pigs and rabbits - in 2-4 days. Dead animals are opened, smears and cultures are made from the blood of the heart, spleen, liver and infiltrate at the injection site of the test material. Identification. The causative agent of anthrax should be differentiated from saprophytic bacilli: B. cereus, B. megaterium, B. mycoides And B. subtilis based on the main and additional features. The main features include pathogenicity, capsule formation, pearl necklace test, phage lisability, immunofluorescence test. Additional are mobility, lack of hemolysis, lecithinase activity, phosphatase formation.
| Test | B. anthracis | B. cereus, B. megaterium, B. mycoides, B. subtilis |
|---|---|---|
| pathogenicity | Pathogenic for laboratory animals | Not pathogenic for laboratory animals, with the exception of B.cereus (with intraperitoneal infection of white mice). |
| Capsulation | Forms a massive with clear |
The capsule does not form.  |
| "Pearl necklace" | On penicillin agar, the pathogen grows in chains, consisting of spherical shapes resembling a pearl necklace. |
The “pearl necklace” phenomenon is absent. |
| Lysability by phage | Lysed by anthrax phage. |
Lysis by anthrax phage is absent. |
| Immunofluorescent test 1 |
contours of the capsule.1
- an indicative method and requires additional study of virulence, capsule formation, phage sensitivity.
2
- the trait is variable in different strains.
Serological study.
To detect anthrax antigens in the study of leather and fur raw materials, rotten pathological material, as well as fresh pathological material and serological identification of isolated cultures, the Ascoli precipitation reaction is used. As a serological test, mainly for studying the antigenic spectrum of Bacillus anthracis, the diffusion precipitation reaction is used ( RDP). To identify fresh cases and retrospective diagnosis of anthrax in humans, the allergen anthraxin was proposed (EN Shlyakhov, 1961). They also reveal specific post-vaccination sensitization in farm animals.
Immunity.
The formation of immunity to infection by the type of antitoxic causes a protective antigen. Currently, protective antibodies have been detected using RSK, RDP and an indirect variant of the method of fluorescent antibodies. live spore anthrax vaccines are used: STI vaccine (immunity occurs after 10 days and lasts at least 12 months), vaccine from strain No. 55 (immunity occurs after 10 days and lasts at least 1 year). For treatment and passive prophylaxis, anti-anthrax serum and globulin. Immunity occurs within a few hours and lasts up to 14 days.
These pathogens cause infections that belong to the group of especially dangerous ones (of bacterial infections, they include plague, cholera, anthrax, tularemia, glanders and brucellosis).
Anthrax.
The causative agent of anthrax - Bacillus anthracis belongs to the genus Bacillus of the family Bacillaceae (bacilli).
Morphology. Large Gram-positive rod, often with rounded ends. Unlike other bacilli, it is immobile, stains well with aniline dyes. In clinical materials, they are located in pairs or in the form of short chains surrounded by a common capsule (it is formed only in the human body and animals or on special media with blood, blood serum). On media, the pathogen forms long chains in the form of “ bamboo cane” (with refinements at the ends and articulations of cells). On agar containing penicillin, cell walls are destroyed, spherical protoplasts are formed in the form of chains (“ Pearl necklace”). The causative agent of anthrax forms endospores, which are located centrally, their diameter does not exceed the diameter of the bacterial cell. Spores are formed only outside the body, in the presence (access) of oxygen and a certain temperature (from +12 to +43 o C, optimum at 30-35 o C). Spores exhibit very high stability in the external environment (decades). Anthrax is primarily a soil infection.
cultural properties. The pathogen grows in aerobic and facultative - anaerobic conditions. Temperature optimum +37 o C, pH -7.2-7.6. Grows on simple nutrient media, incl. on potatoes, straw infusion, extracts of cereals and legumes. Gives characteristic growth when sown by injection into gelatin (“ upside down herringbone”). Virulent R-forms on dense media form rough grayish-white colonies of a fibrous structure (“ jellyfish head" or " lion's mane”). On liquid media, a precipitate is formed in the form of a lump of cotton wool. Anthrax can also form smooth (S), slimy (M), or mixed (SM) colonies, especially under microaerophilic conditions. In the S-form, the pathogen loses its virulence.
biochemical properties. B.anthracis is biochemically highly active. It ferments glucose, sucrose, maltose, trehalose with the formation of acid without gas, forms hydrogen sulfide, coagulates and peptonizes milk.
Antigenic structure. There are three main groups of antigens - capsular antigen, toxin (encoded by plasmids, in their absence strains are avirulent), somatic antigens.
Capsular antigens differ in chemical structure from K-antigens of other bacteria, polypeptide nature, are formed mainly in the host organism.
Somatic antigens- polysaccharides of the cell wall, thermostable, long-lasting in the external environment, corpses. They are detected in the Ascoli thermoprecipitation reaction.
Toxin includes a protective antigen (induces the synthesis of protective antibodies), a lethal factor, an edematous factor.
pathogenicity factors- capsule and toxin.
Brief epidemiological characteristics. Anthrax is a zoonotic infection. The main source for humans is herbivores. Their infection occurs mainly by the alimentary route, spores remain in the soil for a long time and are swallowed by animals mainly with feed, grass). Of particular danger are anthrax cattle burial grounds (spores remain in them for a long time, when they are torn, washed out and other processes fall on the surface of the soil and plants). A person becomes infected by contact with infected material (caring for sick animals, cutting and eating infected meat products, contact with the skins of anthrax animals, etc.).
The main forms of clinical manifestation depend on the entrance gate of infection - skin (carbuncle), intestinal, pulmonary, septic. Characterized by high mortality (less in the skin form).
Laboratory diagnostics. Material for research from patients depends on the clinical form. In the skin form, the contents of the vesicles, the discharge of the carbuncle or ulcers are examined, in the intestinal form - feces and urine, in the pulmonary form - sputum, in the septic form - blood. Objects of the external environment, material from animals, food products are subject to research.
Bacterioscopic method used to detect gram-positive rods surrounded by a capsule in materials from humans and animals, spores - from environmental objects. The most commonly used method is fluorescent antibodies (MFA), which allows the detection of capsular antigens and spores.
Main method - bacteriological it is used in laboratories of especially dangerous infections according to the standard scheme with inoculation on simple nutrient media (MPA, yeast medium, GKI medium), determination of mobility, Gram staining and study of biochemical characteristics. In differentiation from other representatives of the genus Bacillus, a biological test is essential. White mice die within two days, guinea pigs and rabbits within four days. They also define lysability by bacteriophages, sensitivity to penicillin (pearl necklace). For retrospective diagnosis, serological tests are used, an allergic test with anthraxin, to detect a somatic antigen - the Ascoli reaction, which can be effective with negative results of bacteriological studies.
Treatment. Anti-anthrax immunoglobulin, antibiotics (penicillins, tetracyclines, etc.) are used.
Prevention. A live spore-free STI vaccine, a protective antigen, is used.
Ministry of Science and Education of the Russian Federation
Moscow State University applied biotechnology
Department of Microbiology and Immunology
"The causative agent of anthrax"
Completed: student vet.-san. f-ta
II course, 9 groups
Budantsev M.V.
Checked:
Prof. Skorodumov D.I.
Moscow 2005
Introduction
1. Characteristics of the exciter
1.1 Morphological properties
1.2 Enzymatic activity
1.3 Antigenic structure
1.4 Pathogen resistance
2. Evolution
Conclusion
Bibliography
Introduction
The causative agent of anthrax - Bacillus anthracis - belongs to the order Eubacteriales, the family Bacillacae, the genus and subgenus Bacillus. Bacillus was first discovered under a microscope by F. Pollender in Germany in 1849. In 1850
K. Daven and Hans in France identified filamentous immobile little bodies (cylindrical rods) in the blood of sheep that died from anthrax. In Russia, F. Brauel in 1857 found rods (vibrios) in the blood of a person who died of anthrax, and experimentally reproduced the disease in animals, infecting them with blood containing these microbes. But the meaning of the sticks remained unclear. Only in 1863, K. Davep finally established that they are the causative agent of anthrax. This year is considered the official date of the discovery of the anthrax bacillus.
The culture of pathogens was obtained only in 1876. First, R. Koch, and then L. Pastor. Independently of each other, they infected animals with this culture, reproduced the disease, and discovered that anthrax bacilli are capable of forming spores. In 1888, Serafini found a capsule in anthrax bacilli. In Russia, the culture of the anthrax microbe was first obtained by V.K. Vysokovich (1882).
The genus Bacillus unites 48 species of aerobic or facultative anaerobic bacilli, which are divided into two groups: the first includes 22 species, the second - 20 species. Better studied are the bacilli of the first group. The species closest to the anthrax bacillus are: You. cereus is a waxy bacillus of Bac. cereus var.mycoides sive - root-shaped bacillus; You. megaterium - cabbage bacillus; You. subtilis sive - hay bacillus; You. pumilus sive is the potato bacillus. All of them are saprophytes, except for you. sereus, which synthesizes the active pathogenicity enzyme lecithinase and is capable of causing food toxicosis.
1. Characteristics of the exciter
1.1 Morphological properties
In unstained preparations prepared from the blood and tissues of animals sick or dead from anthrax, bacilli have the form of homogeneous transparent rods with slightly rounded ends. They lie singly or are connected in short chains. The number of cells in a chain in highly virulent strains, as a rule, does not exceed three, while in low virulent strains there may be more.
Bacilli grown on solid or liquid nutrient media form chains of different lengths. In smears of cultures of strains that gave typical growth in the form of a flocculent sediment in liquid nutrient media, the rods are more often arranged in long chains, and in those made from cultures with atypical diffuse growth, they form short chains. Cells in chains are of unequal size and resemble cylinders. The cell surface is uneven.
In the painted chains, the ends of the sticks facing each other are straight, as if chopped off, while the free ends are slightly rounded. Bacilli synthesizing a capsule during growth on media containing proteins and reproduction in the body of animals form chains in the form of a bamboo cane, the truncated ends of the cells are somewhat depressed and symmetrically thickened at the joints.
Bacilli have a nucleus. F.Ya. Kitaev (1922) established that it takes part in the division of vegetative cells and is often found in germinating spores. Later, the presence of a nucleus in the bacillus was confirmed by Flewett (1948). In 1959 M.P. Meisel and L.V. Mirolyubov determined that the nucleus consists of spiral threads occupying the central part of the cell and located along its axis. The nucleoid is represented mainly by a network of fibrils lying randomly, evenly over its entire area. Chatterjee and Williams (1962) indicate that cells from young cultures have long chromatin bodies. continuous formations located centrally. In mature cells, they are both continuous and; and divided into halves. In the cells of 24-hour cultures, long chromatin bodies are arranged in large complexes consisting of spherical formations. The authors concluded that the anthrax bacillus has a differentiated discrete nucleoid.
The differentiation of the nucleoid was confirmed by G. V. Dunaev (1967, 1972) when he studied vegetative cells of Tsenkovsky vaccine strains II and STI-1, fixed and stained by the Pekarsky-Robinow method. A clearly contoured nucleoid was found in bacilli at all phases of their development. The structure of the nucleus is especially well revealed with combined fluorescent and head-contrast microscopy. DNA and RNA are found in bacilli, the first is contained in the nucleoid, the second is in the cytoplasm.
The DNA chromosome molecule is double-stranded, closed in a ring and peculiarly packed in the form of a fibrous strand resembling a twisted straw bundle. The compact form of DNA is maintained by single-stranded ribonucleic acid, which in turn is associated with RNA polymerase and cationic proteins. The length of the elongated DNA nucleoid molecule is almost 2 times the length of the bacillus itself.
The submicroscopic structure of anthrax bacilli was first reported by Roth and Williams (1963, 1964); they found elements of a discrete nucleoid in the vegetative cells of the microbe. Then a number of Soviet and foreign investigators (Pavlova and Kats, 1966; Moberly, Shafa and Gerchardi, 1966; Belokozov, 1970; Trzhetsetskaya and Kulikovskii, 1972; and others) studied in some detail the structure of virulent (nos. 66 and 2222) and vaccine Tsenkovsky, STI-1, Stern) strains of bacilli.
Obviously, the bacillus, which is capable of vegetation in the external environment and in the animal organism, has highly developed regulatory mechanisms that ensure metabolism and vital activity during changes in the environment. The perfect adaptation system depends on the morphological structure of the cell. The wall of the bacillus consists of three layers: two osmiophilic and one osmiophobic. But such a structure is not always revealed. More often, the wall consists of inner osmiophilic, more dense, and outer, moderately dense layers. The outer layer often passes into fibrillar structures located over the entire surface of the cell. It is believed that these osmiophilic fibrillar formations are the remnants of the capsule.
In the cell wall, tubules are visible that connect to the cytoplasmic membrane and open into the external environment.
The cytoplasmic membrane is smooth or somewhat tortuous. Only in some parts of the cell are its three layers visible; they are better seen in lysed bacilli. More often, the membrane is tightly adjacent to the cell wall, and it is revealed as a single layer. The membrane has protrusions into the cytoplasm, differing in shape, size, structure and localization; they are described as intracytoplasmic membrane structures. The protrusions are in the form of curls, ovals and uneven lines, in many bacilli they penetrate into the nucleoid zone.
In the cytoplasm of bacilli, clearly contoured vacuoles are found. Usually they are large, limited by a membrane that serves as their frame. On the outside of it are ribosomes. They are arranged in chains, forming polyribosomes. The latter are better seen in lysed cells. Quite often, vacuoles are concentrated near the nucleoid. Gerhardi (1967) believes that vacuoles arise as a result of the dissolution during fixation and dehydration of inclusions of a lipid nature and, above all, poly-ß-hydroxybutyric acid granules.
In bacilli are lipoprotein granules located mainly subterminally and terminally. Mesosomes (mitochondrial equivalents) have also been identified. They have the form of clearly contoured, brightly glowing yellow-green granules in contact with the cytoplasmic membrane. Mesosomes are polyfunctional. The membrane-mesosomal system of bacilli is responsible for oxidative phosphorylation, electron transfer, the implementation of the cycle of di- and tricarboxylic acids, it is also involved in protein synthesis (Burd, 1967; 1968). In the cytoplasm, after staining with an aged solution of methylene blue according to Loeffler, in the polar regions of the bacillus, and sometimes in the central part, currencyine granules are found, stained metachromatically.
When stained with Sudan black, lipid granules are noticeable, which are especially numerous during the period of sporulation. They are found in spore-forming aerobic bacilli of all kinds, including saprophytes. The cytochemical reaction of Hotchkiss pas polysaccharides reveal small granules of glycogen. They are contained in both ordinary and spore-forming bacilli.
Bacilli reproduce by division. A transverse partition is formed in the cell, which divides it into two equal-half individuals. The formation of a septum begins with the invagination of the cytoplasmic membrane and the involvement of the cell wall in this process. Gradually, the cell seems to be laced up. However, often a new cell division begins before the completion of the first division, which leads to the formation of streptobacillus. The resulting chain consists of cells of different lengths.
Bacilli secrete exotoxin, which plays a leading pathogenetic role in the development of the disease. In the process of biosynthesis and secretion of exotoxin during the cultivation of bacilli on special media, intensive development of the ribosomal and membrane-mesosomal apparatuses is noted, a close relationship is established between them, and intracytoplasmic membrane structures penetrate into the nucleoid zone. In the exponential phase of growth, the culture consists mainly of nondividing cells (Dunaev, 1972).
A large accumulation of osmophilic masses is observed in the nucleoid zone. In some parts of the cells, intracytoplasmic channels are found that differ in morphology from the usual type of membrane structures in microbes of this species. They are straight and short. The channels pass through the cell wall and communicate with the environment. Single cells are found with a lysed protoplast, but well-preserved membrane structures. These cells often have areas of destroyed cell walls.
In this phase, the bacilli secrete the toxin. It can be transported from the bacillary cell in three ways: the toxin exits through special channels, through the undamaged but altered cell wall, and through sections of the lysed cell wall. In the plasma of bacilli there are inclusions of compact osmiophilic particles. Outside the microbe, they are located in a less optically dense substance, also secreted by bacilli. As they move away from the bacilli, the particles become larger and the distance between them increases. The described structure of bacilli is typical for vaccine and virulent strains of anthrax.
Capsule formation. Bacilli in the body of an animal and when cultivated on nutrient media with a high content of native protein form a capsule. It does not form in the presence of atmospheric oxygen. The capsule is the outer mucous layer of the bacillus, it is considered as a layer of ectoplasm. On ultrasections, it is visible as a compact thick layer closely adjacent to the wall of the vegetative cell.
The capsule has several layers. The inner part of it is formed by acid mucopolysaccharides, the middle part - by protein-polysaccharide complexes, the outer part - by mucopeptides and polypeptides. In the outer layers of the capsule and in the cell membrane, mucopeptides differ in their properties. The capsule, consisting of 98% water, has a protective osmotic effect against the influx of large amounts of water into the bacillus and protects it from dehydration, as well as from various environmental influences, including the body's immune mechanisms. The capsule prevents phagocytosis
You. anthracis and contributes, according to N.N. Ginsburg et al. (1960), fixing them to the cells of the macroorganism. It is believed that it determines the degree of virulence of bacilli. Capsular anthrax bacilli lack these properties. The capsule is formed in both liquid and solid whey nutrient media. When grown on Gladstone and Fields medium, the capsule begins to be detected in some bacilli after 3 hours of incubation (Mashkov and Bodisko, 1958), and by 14-10 hours almost all of them have it. Then there is diffusion of the capsular substance from the surface of the cells into environment. Capsules are also well formed during the growth of bacilli in horse blood serum according to Schaefer, on serum agar, especially with an excess of CO2, and also when grown in protein media used to obtain a protective antigen. In this case, the formation of a capsule begins after 2 "/2 hours of growth, and this process is well expressed in a six-hour culture; capsules are also found in cells after 24 hours of growth. The GKI protein medium is an elective substrate for capsule biosynthesis. Capsule formation, in addition to native protein, is alkaline environment and the presence of CO. Eastin and Thorne (1963) established the effect of CO2 on the activity of some mitochondrial enzymes in bacilli Virulent bacilli require a higher concentration of CO2 during the formation of the capsular polypeptide.
For the synthesis of the most important virulence factor - capsules - the amino acids leucine, valine and methionine are necessary. Virulent strains of bacilli require hypoxanthine, methionine, alanine, and tryptophan for optimal reproduction. The degree of virulence is largely determined by the growing conditions of bacilli and the composition of the medium.
In the exponential growth phase of the culture of virulent vaccine strains, along with capsular ones, non-capsular bacilli are also detected. This indicates that mutants with other genetic properties, without the capsular glutamic acid polypeptide, appear in the strain population.
In the body of an animal, bacilli with capsules are found 2-3 hours after infection, but during this period they are found only at the injection sites and regional lymph nodes. They are surrounded by tissue detritus and are located in areas (light), delighted with the action of the microbe toxin. When bacilli enter the immune organism, capsules seem to form very slowly and quite rarely. Morphologically, the capsules of bacilli that multiply in the body and grown on nutrient media, but have differences, only in the latter the capsule is more massive. The capsule is more resistant to decay processes than the bacillus itself, therefore, in the rotting corpse of an animal that has fallen from anthrax, only “shadows of microbes”, empty capsules, are found.
Dispute formation. Biological role the dispute is that they are a form of preservation of the species of bacilli under adverse conditions of existence. Spores can stay in nature for a long time, and therefore, retain the substrate of the genetic information of the original cells (genome) for a long time and thereby ensure the transfer of the main properties to the offspring of subsequent generations.
Sporulation occurs in media with a neutral or slightly alkaline reaction with a deficiency of protein substances. Spores are formed in saline, distilled water, in non-fixed smears. It has been established that this process occurs faster in an environment containing pure oxygen than when the culture is aerated. atmospheric air. An educated dispute begins from the moment when the ratio of the forms of protein and mineral nitrogen in the medium shifts towards the predominance of the latter (Egorov and Siitsin, 1961). The addition of neutral sodium oxalate to the medium activates sporulation, and a 1% solution of calcium chloride suppresses it. Spores are not formed in environments rich in protein substances, such as blood and blood serum, in a living organism and an unopened corpse. If the integrity of the corpse is violated, sporulation is possible.
Vegetative cells that form spores (sporangia) contain one spore located centrally or subterminally. The spore diameter does not exceed the width of the bacillus. Spore formation begins at the moment of transition of the vegetative cell to the stationary phase of growth, while a number of successive stages are observed:
1. Two nucleoids are formed in the cell, which soon combine into a rod-shaped formation.
2. Protrusions appear in one area of the cell cell membrane with mesosome. They form a transverse partition that separates the part of the cytoplasm and DNA free from lipoprotein grains from the rest of the cell contents. As a result, the site of the future spore, surrounded by a membrane, is isolated.
3. An isolated area is surrounded by a cell membrane; a prospore with a double membrane is formed.
4. The space between the spore and cell (second) membranes expands, its contents become homogeneous, the so-called cortex arises, due to which the spore is more visible under microscopic examination.
5. A shell is formed around the outer membrane covering the cortex. Of all the spore structures, it is distinguished by the greatest ability to scatter electrons. Then the spore membrane is covered with a looser and thinner layer - the exosporium. The formed spore exits the bacillus through a gap in the cell wall. Spores do not germinate inside the bacillus.
Thus, the formed spore consists of the following main layers:
Sporoplasma (its central part). It consists of a homogeneous material with fine-grained osmiophilic granules; the nucleoid is found in the form of a fuzzy contoured zone of osmiophobic material;
Cytoplasmic inner membrane surrounding the sarcoplasm;
Cortex located on the surface of the cytoplasmic membrane. It is represented by a massive light optical layer, consists of peptidoglycan. From its inner layer, a shell is formed during spore germination:
The outer bilayer membrane of the spore is thick and overlying the cortex;
The layer of cytoplasm between the outer membrane and the membrane
Spore shells, according to I.I. Belokonova (1970), T.A. Tresetskaya, L.V. Kulikovsky (1972), it has up to 6 layers; the inner side of the shell is adjacent to the outer membrane of the spore, on the outer side it has multiple protrusions;
Exosporium.
Spores are oval, sometimes rounded formations that strongly refract light. The length of rotten spores is 1.2-1.5 microns, the width is 0.8-1 microns, immature ones (prospores) are somewhat less. Mature spores, shaded with chromium or contrasted with phosphotungstic acid, are detected in an electron microscope as optically impenetrable formations with uneven contours; younger spores and prospores are homogeneous, dark. The method of carbon replicas according to Bredli and Williams (1957) makes it possible to detect ribs on the surface of spores. They are located longitudinally or in the form of cells and are more clearly expressed in spores from old cultures (15 days) (Belokonov, 1970). Shafa and Sato (1966), who studied the Stern strain, found villi on the surface of the exosporium. Their presence was confirmed
I.I. Belokonov (1970), who taught vaccine strains STI-1 and II of the Tsenkovsky vaccine.
The spores of the STI-1 vaccine strain were found to have paro-spore bodies, similar topics, which have previously been described in some saprophytic spore-forming microbes. They have a regular spherical shape, are located on the surface of the spores or lie separately. Their diameter is different: small 1200. A, medium 1564 A and large 2000 A. The significance of these bodies has not been clarified (Dunaev and Belokonov, 1968).
The beginning of spore formation depends on the characteristics of the strain and the temperature of the medium. At 30-37°C, it usually ends after 1-2 hours, at 24°C - after 16 hours, at 18°C it lasts up to 70 hours. Below 15°C and above 42C, sporulation does not occur. In some strains, this process begins intensively 18-20 hours after the inoculation of the medium and cultivation at 37°C (Belokonov, 1970; Avakyan, Kats, Pavlova, 1972). In dense media, spores are formed faster than in liquid ones. The process of their formation in well-sporulating strains usually ends on MPA in 48-72 hours.
Spore germination requires amino acids (nitrogen source), carbohydrates (especially glucose), and nucleic acid precursors, 1-alanine and 1-tyrosine (Zemskov et al., .1972).
Morphological changes indicating the beginning of spore germination are detected 5-10 minutes after inoculation on a nutrient medium (temperature 37°C). They are characterized by swelling of spores and the appearance of small light areas along their periphery. The germinating spore loses its luster, takes on a spherical shape, then stretches again and a bacillus emerges from one end of it in the direction of the longitudinal axis, shedding the spore membrane; the released bacillus is similar to the maternal anthrax bacillus, only it has more rounded ends.
Chemical composition. The dry residue of vegetative cells contains 6.8% nitrogen and 12-13.5% mineral ash; the dry residue of spores contains 12.14 and 41.15%, respectively. The amount of DNA varies depending on the strain. Most high level RNA is observed in bacteria that are in the exponential growth phase. Anthrax bacilli have enzymes: lipase, diastase, protease, gelatinase. dehydrase, cytochrome oxidase, peroxidase, catalase, arginase, etc.
A somatic antigen was isolated from the body of the microbe, which includes a polysaccharide containing N-acetylglucosamine and galactose in equimolecular proportions, as well as a small amount of 0-acetyl and amino acid residues.
In the composition of the shell and capsule of the anthrax microbe, 3 antigenic complexes were found:
surface antigens of the capsule, which are apparently peptides, sensitive to the action of pepsin and partially trypsin;
the actual capsular antigens, located in the main layer of the capsule, contain substances of a protein-polysaccharide nature that are sensitive to the action of trypsin, chemotrypsin, hyalurondase and lysozyme;
cell envelope antigens containing substances of both a polysaccharide and protein nature, sensitive to the action of lysozyme and trypsin (Levina and Katz, 1964; Lvakyan et al., 1907).
According to E.P. Levina and L.P. Katz, antigens detected using fluorescent anthrax serum are localized in the shell. The spores contain alanine racelease, nucleoside ribosidase, and adenosine deaminase. In resting spores, these enzymes provide a weak level of energy metabolism (respiration).
1.2 Enzymatic activity
Of the large group of aerobic bacilli living in the soil, only Bacillus anthracis has acquired the most pronounced virulent properties and the ability to cause fatal disease in animals and humans. It has a number of similar morphological and cultural properties with these non-pathogenic spore-forming microbes. Especially many identical signs are soaked in Bacillus anthracis and you. segeus. There is a lot of factual material regarding the toxicogenicity of you. segeus and its biochemical activity.
Electron microscopic examination of both bacilli (Shakhbanov, 1975) revealed both common characteristic and atypical features. Thus, the cell wall in Bac. anthracis is thicker and has fibrillar material inside, and you have. cereus mushroom-shaped outgrowths are located on the wall. I.B. Pavlova and L.P. Katz (1966) found in Bac. anthracis have more developed membrane structures, which, in their opinion, is caused by a greater activity of redox enzymes. You. cereus in contrast to Bac. anthracis rapidly coagulates egg yolk solutions; has an extremely active lecithinase. It slowly reduces methylene blue, weakly reduces nitrates and nitrites, produces gelatinase, as well as protease, and rather quickly hydrolyzes gelatin and curdled whey.
1.3 Antigenic structure
You. anthracis has not yet been studied enough.
N.F. Gamaleya (1928) established that the subcutaneous edema formed at the injection site of the pathogen contained poisonous substances that, when injected into the blood, caused rapid death of the rabbit. Watson, Bloom (1947) obtained extracts from the edema of rabbits with anthrax. After intradermal administration of extracts to animals, the same histological changes were recorded as after infection with cast bacilli. In rabbits, these extracts caused the formation of immunity, it manifested itself to a weak degree in guinea pigs and white mice.
Watson and Co11 (1947) isolated two substances from the bacillus, they differed in physical, chemical and biological properties. The first of them caused tissue inflammation, aspired to the anode, reacted with Ca phosphate, the second was of a protein nature, was non-toxic, and had immunizing properties.
In 1953, Smith and Co11 isolated anthrax exotoxin from the blood plasma of guinea pigs that died from this disease, and then from the culture fluid during the cultivation of Bac. anthracis on a liquid nutrient medium. It has been established that the toxin is not related, as previously believed, to the capsular substance consisting of polyglutamic acid, but it is closely related to the protective antigen.
Smith (1958) found that the toxin is contained not only in the edematous fluid, but also in a fairly high concentration in the blood plasma and in a smaller amount in the pleural and peritoneal exudates. The toxin caused not only a local inflammatory reaction (edema) with tissue destruction phenomena, but also the death of guinea pigs and white mice from secondary shock. This toxic substance was designated as a lethal factor, and in 1955 it was named anthrax toxin.
Anthrax antisera obtained from horses hyperimmunized with both capsular and non-capsular strains of bacilli suppressed the action of the toxin. This indicated that the origin of the toxin was not related to the capsule. The toxin was also neutralized by the serum of rabbits immunized with the projective antigen.
Evans (1954) isolated anthrax exotoxin in vitro. Smith (1958) found that virulent and non-encapsulated vaccine strains synthesize toxins of the same potency. The toxin had the maximum strength by I "/2 hours from the start of incubation. Its amount was directly dependent on the number of bacteria in the culture. In terms of its properties, the toxin obtained in the culture did not differ from that synthesized by bacilli in vitro; it caused the formation of antibodies in animals and neutralized with horse anthrax serum.
In 1958, Smith determined that native anthrax toxin clearly distinguished between edematous and lethal factors. Molner and Strange (1960) divided the toxin into two factors. One of them passed through a glass filter and had the properties of a protective antigen, the second was retained on the filter, but was easily eluted by treatment with 0.1 M carbonate buffer at pH 9.7. Both factors in themselves were not toxic, but their mixture showed a pronounced toxic effect - it caused inflammatory reactions in the skin of guinea pigs and the death of mice. It was found that the second factor consists of two antigens.
Stanley and Smith (1961) showed that, in addition to these two factors (components), there is one more that is serologically different from them; it was present in the toxin produced both in the body and in culture. These factors were labeled I, II and III. Veal, Tylor, (1962) proposed other designations: EF (edematogenous or inflammatory factor); RA (immunogenic protective antigen) and LF (lethal factor), which corresponded to I, II and III factors.
Therefore, a mixture of I and II components has toxic properties (capillary permeability increases, which causes edema). But component II has projective properties, causing nmmunogenic processes in the body. The addition of component I to it significantly increases its immunogenicity, but when mixed with component III, the protective properties decrease. Component III is not toxic but when added to component II imparts lethal properties to the mixture. All three components of the toxin constitute a synergistic mixture that has both edematogenous and lethal effects. This shows that the anthrax toxin is a three-component system. The full complex of anthrax toxin synthesized in vitro is neutralized by therapeutic anti-anthrax globulin (Fedotova, Ulanova, 1970).
All three components of anthrax extracellular toxin have antigenic properties and are serologically active. A toxin synthesized in vivo differs from a toxin produced in vitro in that it has a faster lethal effect and is difficult to detect.
It was found that the causative agent of anthrax has a number of antigens: a polysaccharide complex; capsular polypeptide; exotoxin, which includes three components - inflammatory, immunogenic (protective antigen) and lethal. Each of the microbial agents (toxins, surfactants, nucleic acids etc.) interacts only with strictly defined molecular targets in the attacked cells. They act only on those molecules with which they have a chemical affinity, supplemented by the correspondence of structures and functions, i.e., chemical complementarity. If there are no suitable targets, then the microbial attack is ineffective. This is the secret of hereditary immunity. Changing the arrangement of complementary amino acids (single out of many) creates immunity (Rumyantsev, 1984).
The virulence of anthrax bacilli is determined by two aggression factors: a capsule representing a d-glutamic acid polypeptide; exotoxin, consisting of three individually non-toxic protein components; a mixture of them, as indicated above, causes swelling and lethality.
The first antigen isolated from Bac.anthracis was a polysaccharide (somatic) complex. It is serologically and chemically related to Bac polysaccharides. cereus and type IV pneumococci. According to
Yu.V. Ezepchuk (1968), the lack of apparent specificity in polysaccharides suggests that they perform in you. anthracis only a structural function and not (are related to pathogenicity factors.
Another antigen is a capsular polypeptide, serologically truncated; it is also found in saprophytic spore-forming bacilli.
The capsular polypeptide is considered as one of the important factors of anthrax bacilli aggression, since it suppresses the protective phagocytic reaction of the body, increases the activity of the lethal factor of extracellular anthrax toxin and simultaneously suppresses opsonization. However, the somatic polysaccharide and capsular polypeitide of glutamic acid of bacilli are not capable of causing the synthesis of antibodies that determine the background of the specific humoral defense of the animal organism against the anthrax pathogen. This role in bacilli is performed by a protective antigen (component II) - an extracellular substance of a protein nature synthesized during the metabolic activity of a microbe in an animal organism or on special nutrient media and released bacterial cell into the environment.
Being one of the pathogenicity factors, the immunogenic component of the anthrax microbe determines the formation of immunity to this infection by the type of antitoxic (Stanley and Smith, 1963). It serves as a carrier of specific protective properties.
The available data indicate a significant role of bacillus exotoxin in the manifestation of many typical features of the infectious process and the formation of specific body defenses. This gives reason to consider it as a factor that determines the pathogenesis and immunity in anthrax.
1.4 Sustainability
The stability and duration of survival of bacilli and their spores are different. The former are relatively labile, the latter are quite resistant. Bacilli in the soft tissues of an unopened corpse can persist for 2-4 days. (Ipatenko, 1982), as they are destroyed under the influence of proteolytic enzymes. In the bone marrow of intact bones, this process occurs somewhat later - bacilli remain viable here for up to 7 days (Franke, 1964; Ipatenko, 1964-1982).
Bacilli do not withstand positive temperatures for long. Direct sunlight kills them in a few hours. When heated to 50-55 ° C, they die within an hour, at 60 ° C - after 15 minutes, at 75 ° C - after a minute, when boiled - instantly. Fast drying kills the bacillus, while slow drying leads to spore formation. Bacilli can die after 2 weeks at 2-4°C. In the gastric juice of animals, bacilli die within 30 minutes; in salted meat they persist for up to 15 days.
Sub-zero temperatures conserve bacilli. So, at -10 ° C they survive 24 days, at -24 ° C - 12 days, in frozen meat at -15 ° C - up to 15 days. They can be preserved even at temperatures liquid nitrogen(-196°C).
Bacilli are not resistant to various chemicals. Alcohol, ether, 2% formalin solution, 5% phenol solution, sublimate solution 1: 1000.5-10% chloramine solutions, fresh 5% bleach solution, hydrogen peroxide destroy them in 4-5 min. Methyl bromide reliably kills bacilli. OKEBM (suspension of one weight part of ethylene oxide and 2.5 methyl bromide).
Fresh milk also has bacteriostatic properties (it delays the development of bacilli), but this effect lasts only 24 hours, later the bacilli begin to multiply, form spores, retaining their inherent pathogenicity. The antimicrobial properties of milk are due to lysozyme and lactins, products of enzymatic oxidation (Abdullin and Kaparovich, 1971; Ipatenko, 1982). The growth of bacilli can be delayed by the fresh blood of animals (Ipatenko, 1964-1982).
Bacilli are sensitive to the action of certain antibiotics - penicillin, streptomycin, oxytetracycline, tetracycline, and biomycin. Bacteriostatic properties appear both in vitro and in vivo. The minimum concentrations of streptomycin that inhibit the growth of bacilli range from 1.15-2.34 µg/ml; oxytetracycline - 0.22-1.87 μg / ml (Ipatenko, 1983).
When growing on MPA, bacilli take the form of balls under the influence of low doses of penicillin. Their chains take the form of a "pearl necklace". This reaction is specific and can be used for accelerated differential diagnosis.
The antimicrobial effect of streptomycin and oxytetracycline on virulent and vaccine strains, taken separately and in combination, is not the same. A mixture of streptomycin with oxytetracycline has a more pronounced effect than either of them separately. Their identical total concentrations in micrograms per 1 ml of medium exceed the effect of oxytetracycline by 2 times and by streptomycin by 4 times (Novikov, 1960). It should be borne in mind that in nature there are individuals of bacilli that are resistant to antibiotics.
dispute persistence. Spores are much more stable than the vegetative forms of bacilli and last longer in the external environment. The high resistance of spores to various influences is associated with the presence of a dense multilayered shell, low water content in it, and the absence of enzymatic activity. One of the most important factors contributing to the high resistance of spores is the presence of the calcium salt of dipicolinic acid; the calcium content in spores is much higher than in vegetative bodies.
The resistance of spores largely depends on how quickly they formed. Spores formed at 18-20°C are more resistant than spores formed at temperatures of 35-38°C (Revo, 1931). Spores can, under certain conditions, remain viable and virulent in the external environment (soil) for decades (Ipatenko, 1982).
Drying has no effect on spores. In dried agar and gelatin cultures, spores remain viable and virulent up to 55 years. Direct sunlight destroys spores only after 4 days (Franke, 1964; Ipatenko. 1982), but ultraviolet rays and X-rays have a detrimental effect on them - spores die after - 20 hours. Dry heat (120-140 ° C) kills spores only after 2-3 hours, at 150°C they die after 1 hour, fluid steam at 100°C destroys them after 12-15 minutes, autoclaved at 110°C - after 5-10 minutes, boiling - for an hour. At 400 C, the spores die in 20–30 s.
The spores are also resistant to chemicals. Ethyl alcohol in concentrations of 25% and above kills spores only after 50 days, sublimate at a dilution of 1000.5% phenol solution, 5-10% chloramine solutions destroy them after several days (possibly hours), 1% - formalin solution - after 2 hours, 2% formalin solution - after 10 - 15 minutes, 4% potassium permanganate solution - after 15 minutes, 3% hydrogen peroxide solution - after 1 hour, 10% solution caustic soda - after 2 hours. According to M.A. Sefershaeva (1964), spores are resistant to resinous phenols, which are waste products of the oil shale industry.
Active disinfectants with bactericidal sporicidal and fungicidal action were three preparations from the group of interhalogen compounds - hydrochloric acid solution of iodine monochloride (preparations No. 74 and 74-B), pyram and niran, and one preparation from the group of chlorine-active compounds - hypochlor (Boshian, Dmitrieva, 1968 ).
Soil application chemical substances the number of microorganisms does not noticeably change, but inevitably changes their species composition, while disrupting the normal course of microbiological processes in the soil (Konobeyeva, 1964). However, chemical preparations, exposed to the action of soil microbes, can themselves turn into other compounds, even more toxic than the original ones. In this regard, it is necessary to choose especially carefully the means and methods of soil disinfection (Krasilnikov, 1965).
2. Evolution
The question of the origin and evolutionary connections of Bac. anthracis with other soil spore-forming bacilli, including you. cereus remains debatable. Attempts under experimental conditions to turn one type of microbe into another ended in failure. No varieties of Bac. anthracis was not found in nature (Ginsburg, 1960),
Most researchers (Colonies et al., 1970) attribute the occurrence of anthrax as a disease to the Quaternary period, that is, to the time of the widespread settlement of artiodactyls on Earth. The virulent properties of the pathogen at that time were formed under conditions of general susceptibility of animals, the absence of immune livestock among them.
Herbivores (especially ruminants), eating plants, could damage the mucous membrane of the alimentary canal. In these places, soil microbes were able to penetrate into the host organism (Abdullin, 1976). As a result of many such contacts, a mutant capable of capsule formation in the body could have arisen in the microbe. Further, selection for the acquisition of pathogenicity by the capsular microbe in the body, apparently, went towards the release of toxic metabolites.
In the course of evolution, viable offspring of microbes gave rise to mutants that had the main property of the species - to cause disease and death of susceptible animals. With subsequent infections and change of hosts, new properties (primarily virulence) were fixed in the genotype, which are necessary for further reproduction and preservation of the microbe.
Conclusion
The solution to the problem of eliminating anthrax largely depends on the knowledge of the ecology of the pathogen, taking into account the influence of various environmental factors on it, the patterns of the spread of the disease, and the features of its epizootic manifestation. It should be taken into account that the area of distribution of anthrax is associated with soil-geographical zones. Therefore, effective methods for identifying and sanitizing soil foci of the pathogen play an important role.
The fight against anthrax must be based on a well-thought-out plan, which provides for the clarification and elimination of each stationary unfavorable point. Every year there are new data on the epizootology of the disease, the vital activity of the pathogen in the body and in the external environment. Data on its variability are accumulating. Methods of diagnostics, disease prevention and treatment of animals are being improved, new methods of soil disinfection are being developed.
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