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The sap pathogen
Last reviewed: 06.07.2025
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Glanders is an acute infectious disease of zoonotic origin, occurring as septicopyemia in acute or chronic form with the formation of pustules, ulcers, multiple abscesses in various tissues and organs. The causative agent of glanders - 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 the causative agent of sap
The genus Burkholderia belongs to the class Betaproteobacteria. B. mallei is a thin, straight or slightly curved rod with rounded ends, 2-3 µm long and 0.5-1.0 µm wide. It has no flagella, does not form spores or capsules, and is gram-negative. When grown on nutrient media, it is prone to polymorphism: flask-shaped and filiform forms may be present in the preparation, and the cell contours may be uneven. It stains well with all aniline dyes, and bipolarity or unevenness of color is often revealed due to the presence of polyhydroxybutyric acid inclusions. The G + C content in DNA is 69 mol %. It is a strict aerobe, the optimal temperature for growth is 35-37 °C, pH 6.8. It grows well on regular media with the addition of 4-5% glycerol. In MPB with glycerin, uniform turbidity is formed at the beginning of growth, on the second day - parietal growth, turning into a film, from which threads descend downwards. On agar with glycerin at 37 °C, flat translucent colonies appear after a day, which then merge and form thick deposits of a mucous viscous mass of amber color. On potatoes, after a day, delicate translucent colonies are formed, which after a week merge and form a yellow-brown coating, similar to honey.
Biochemical properties are weakly expressed and unstable. Usually ferments glucose, mannitol, xylose with the formation of acid, does not liquefy gelatin. Does not form indole and does not reduce nitrates to nitrites. In liquid media forms hydrogen sulfide and ammonia. Has catalase activity. Curdles, but does not peptonize milk. The beta-galactosidase test is positive; has the enzyme arginine dihydrolase.
In antigenic terms, it is related to the causative agent of melioidosis and some other pseudomonads; at the same time, it has been established that various strains of the glanders causative agent are not uniform in antigenic structure and contain specific polysaccharide and non-specific nucleoprotein antigenic fractions.
The glanders pathogen does not form an exotoxin. When the pathogen is heated for 1-2 hours at 60 °C, an endotoxin is released that actively affects the smooth muscle cells of isolated organs and has a general toxic effect.
In the external environment, the glanders pathogen is unstable. At a temperature of 100 °C, it dies within a few minutes, at 70 °C - within 1 hour. Under the influence of sunlight, in a pure culture, it dies within 24 hours, and in animal excrements it remains for several weeks.
Epidemiology
The source of infection is sick horses, sometimes mules, donkeys, camels, which are infected by direct contact. Animals with acute glanders are especially contagious. The glanders pathogen is contained in secretions from skin lesions and the respiratory system. Humans become infected when caring for sick animals, when in contact with animal carcasses or secondarily infected objects (straw, fodder, harness, etc.). Intralaboratory airborne infection is possible. Transmission of infection from person to person is unlikely. In Russia, glanders have not been registered for a long time. The disease is very rare and is limited to parts of Africa and the Middle East.
Symptoms
The glanders pathogen enters the human body through damaged skin, nasal mucosa, eyes, and also orally and airborne. The penetrated glanders bacilli first multiply in the lymph nodes, then enter the blood and spread throughout the body. The process takes on a septicopyemic character with the formation of multiple scattered foci of purulent melting, ulcers and abscesses are formed. Less often, a chronic course is observed in the form of chroniosepsis with polyarthritis and multiple abscesses in various organs, in the skin, subcutaneous tissue, muscles, on the mucous membranes, with scarring and encapsulation. The incubation period for glanders is from 1 to 5 days, less often 2-3 weeks.
Diagnostics
Diagnostics of glanders includes microscopic examination (RIF, Gram or Romanovsky-Giemsa staining) of the discharge from ulcers, nasal cavity, lymph node or abscess punctate, as well as bacteriological, serological, biological and allergic methods. To isolate a pure culture, pathological material is sown on nutrient media containing potatoes and agar, and in broth with 3% glycerol. Using RPGA and RSC in paired sera of the patient, an increase in the antibody titer is detected, or using RPGA, the pathogen antigen is detected in the material being examined.
Guinea pigs or hamsters are used for infection; they are infected subcutaneously if the material is contaminated with accompanying microflora; or intraperitoneally, if it is a pure culture of the glanders pathogen. Infected males are characterized by the development of testicular lesions, as well as skin abscesses and ulcers. Allergic diagnostics of glanders is carried out by intradermal administration of mallein, obtained from the glanders pathogen during its destruction. The test is based on a delayed-type hypersensitivity reaction, the result is taken into account after 24-48 hours; positive from the 10th-15th day of the disease.