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What causes brucellosis?
Last reviewed: 23.04.2024
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Causes of brucellosis
The cause of brucellosis - representatives of the genus Brucella family Brucellaceae. Human brucellosis can be caused by four species of brucella: B. Melitensis, B. Abortus, B. Suis and B. Canis. The most common cause of the disease is Brucella melitensis, which is subdivided into three biotypes. The main owners are sheep and goats. Fewer occur Brucella abortus, represented by nine biotypes; the main owner is cattle. In the third species of brucella, Brucella suis, 4 biotypes are isolated. The main hosts are pigs (types 1-3), rabbits (type 2) and reindeer (biotype 4). Relatively rare is the disease caused by Brucella canis. The main owner of this microorganism is the dog.
Brucellae are distinguished by pronounced polymorphism, they can be spherical, oval and rod-shaped. Their size is 0.3-0.6 microns for coccal and 0.6-2.5 microns for rod-shaped forms. They are immobile, they do not form a spore, they do not have flagella, they are gram-negative. Grow slowly on complex nutrient media. Brucella - intracellular parasites, they are antigenically homogeneous, contain endotoxin. They differ in significant variability and pass from the S-form to the K- and L-forms. Brucellae are stable in the environment. In water there are more than 2 months, in milk - 40 days, in cheese - 2 months, in raw meat - 3 months, in salted meat - up to 30 days, in wool - up to 4 months. At boiling die instantly, are sensitive to disinfectants, to antibiotics of tetracycline group, aminoglycosides, rifampicin, erythromycin.
[Pathogenesis of brucellosis
The entrance gate of the infection is micro-traumas of the skin, the mucous membranes of the digestive organs and the respiratory tract. At the site of the pathogen introduction, no changes are observed. On the lymphatic pathways brucella reach the regional lymph nodes, but there are no pronounced changes. Reproduction and accumulation of brucella occurs mainly in the lymph nodes, from which they periodically enter the blood, and death is accompanied by the release of endotoxin, causing fever, damage to the autonomic nervous system. With the bloodstream, the pathogen is spread throughout the body, concentrating in organs and tissues rich in macrophages (liver, spleen, muscles, fascia, articular bags, tendons), where, due to incomplete phagocytosis, persists for a long time, causes an inflammatory reaction with the formation of specific granules.
Brucellosis is characterized by a pronounced allergic reconstitution of the body, pronounced HRT, persisting for a long time even after the release of the organism from the pathogen. Allergy plays a big role in the formation of secondary foci of infection. Brucellosis differs propensity to chronic flow, which is associated with a long persistence of brucella in the body. Prior to the introduction of antibiotics in the practice of antibiotics, brucellae persisted in the body for up to two years, a longer course of the disease is associated with the effect of antibiotics: some brucella can go into L-forms and remain intracellularly for a long time.