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Causative agent of glanders
Last reviewed: 23.04.2024
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Sap is an acute infectious disease of the zoonotic nature, proceeding as a septicopyemia in acute or chronic form with the formation of pustules, ulcers, multiple abscesses in various tissues and organs. The causative agent sapa - Burkholderia mallei (according to the old classification - Pseudomonas mallet) was first isolated in pure culture by F. Leffler and H. Schutz in 1882.
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Structure of the causative agent of glanders
The genus Burkholderia is classed as Betaproteobacteria. B. Mallei - a thin straight or slightly curved stick with rounded ends, measuring 2-3 μm in length and 0.5-1.0 μm in width. It has no flagellum, it does not form spores and capsules, it is gram-negative. When grown on nutrient media is prone to polymorphism - in the preparation there may be a flask-shaped, filamentary shape, the contours of the cells may be uneven. It is well stained with all aniline dyes, and bipolarity or color irregularity is frequently detected due to the presence of polyhydroxybutyric acid inclusions. The content of G + C in DNA is 69 mol%. Strict aerobic, optimal temperature for growth 35-37 ° C, pH 6.8. It grows well on conventional media with the addition of 4-5% glycerol. In the BCH with glycerin at the beginning of growth, a uniform clouding is formed, on the second day - near-wall growth, turning into a film from which the threads descend. On agar with glycerol at 37 ° C, flat semi-transparent colonies appear in a day, which then merge and form dense plaque of amber-colored mucus. On potatoes a day later, delicate translucent colonies are formed, which in a week merge and form a yellow-brown plaque, similar to honey.
Biochemical properties are weak and unstable. Usually ferments glucose, mannitol, xylose to form an acid, gelatin does not dilute. Does not form indole and does not restore nitrates to nitrites. On liquid media it forms hydrogen sulphide and ammonia. Has catalase activity. Collapses, but does not peptonize milk. The beta-galactosidase test is positive; has an enzyme arginine-dihydrolase.
Antigenically related to the causative agent of melioidosis and some other pseudomonas; At the same time, it has been established that various strains of the pathogen are not homogeneous over the antigenic structure, they contain specific polysaccharide and nonspecific nucleoprotein antigen fractions.
Exogenous pathogen does not form an exotoxin. When the pathogen is heated for 1-2 hours at 60 ° C, endotoxin is released, which actively acts on the cells of smooth muscles of isolated organs and has a general toxic effect.
In the external environment, the agent of the gland is less stable. At a temperature of 100 ° C perished for several minutes, at 70 ° C - for 1 hour. Under the influence of sunlight, pure culture dies within 24 hours, the excretions of animals persist for several weeks.
Epidemiology
The source of infection is sick horses, sometimes mules, donkeys, camels, which are infected by direct contact. Especially infectious animals with acute form of sapa. The causative agent of sapa is contained in secretions from skin lesions and the respiratory system. Infection of a person occurs when caring for sick animals, in contact with the corpses of animals or secondarily infected objects (straw, forage, harness, etc.). Intralaboratory aerogenic contamination is possible. Transmission of infection from person to person is unlikely. In Russia, sap has long been not registered. The disease is very rare and limited to parts of Africa and the Middle East.
Symptoms
The causative agent of sap penetrates into the human body through damaged skin, nasal mucosa, eyes, and also orally and aerogenically. Penetrating sap stick is first multiplied in the lymph nodes, then penetrates into the blood and spreads throughout the body. The process takes a septiccopemic character with the formation of multiple disseminated foci of purulent fusion, ulcers and abscesses are formed. Less often there is a chronic course in the form of chroniosepsis with polyarthritis and multiple abscesses in various organs, in the skin, subcutaneous tissue, muscles, on mucous membranes, with scarring and encapsulation. Incubation period with sapa from 1 to 5 days, rarely 2-3 weeks.
Diagnostics
Diagnosis of the gland includes a microscopic examination (RIF, Gram stain or Romanovsky-Giemsa) of the separated material from ulcers, nasal cavity, punctate from the lymph node or abscess, as well as bacteriological, serological, biological and allergic methods. To isolate a pure culture, pathological material is sown to nutrient media containing potatoes and agar, and to broth with 3% glycerol. With the help of RPGA and RSK in the paired sera of the patient, an increase in the antibody titer is detected, or with the help of RPHA, an antigen of the pathogen in the test material is detected.
For infection, use guinea pigs or hamsters; infected subcutaneously if the material is contaminated with a concomitant microflora; or intraperitoneally, if it is a pure culture of the causative agent of glanders. Characteristic are the development of infected testicular males, as well as skin abscesses and ulcers. Allergic diagnosis of sap is carried out by intradermal injection of mallein, obtained from the causative agent of sapa during its destruction. The sample is based on the reaction of delayed type hypersensitivity, the result is taken into account after 24-48 hours; positive from the 10th to 15th day of the disease.