Шошқа бруцеллезін қоздыратын бактерия

Bacterium that causes swine brucellosis

Brucella suis is a bacterium that causes swine brucellosis, a zoonosis that affects pigs. The disease typically causes chronic inflammatory lesions in the reproductive organs of susceptible animals or orchitis, and may even affect joints and other organs. Other manifestations are temporary or permanent sterility, lameness, posterior paralysis, spondylitis, and abscess formation. It is transmitted mainly by ingestion of infected tissues or fluids, semen during breeding, and suckling infected animals. Since brucellosis threatens the food supply and causes undulant fever, Brucella suis and other Brucella species (B. melitensis, B. abortus, B. ovis, B. canis) are recognized as potential agricultural, civilian, and military bioterrorism agents.

The most frequent clinical sign following B. suis infection is abortion in pregnant females, reduced milk production, and infertility. Cattle can also be transiently infected when they share pasture or facilities with infected pigs, and B. suis can be transmitted by cow's milk. Swine also develop orchitis (swelling of the testicles), lameness (movement disability), hind limb paralysis, or spondylitis (inflammation in joints). They are also not spore forming, capsulated, or motile. In mouse models, the flagellum is essential for a normal infectious cycle, where the inability to assemble a complete flagellum leads to severe attenuation of the bacteria. Brucella suis is differentiated into five biovars (strains), where biovars 1–3 infect wild boar and domestic pigs, and biovars 1 and 3 may cause severe diseases in humans. In contrast, biovar 2 found in wild boars in Europe shows mild or no clinical signs and cannot infect healthy humans, but does infect pigs and hares.

Phagocytes are an essential component of the host's innate immune system with various antimicrobial defense mechanisms to clear pathogens by oxidative burst, acidification of phagosomes, and fusion of the phagosome and lysosome. B. suis, in return, has developed ways to counteract the host cell defense to survive in the macrophage and to deter host immune responses. B. suis possesses smooth lipopolysaccharide (LPS), which has a full length O chain, as opposed to rough LPS, which has a truncated or no O chain. This structural characteristic allows for B. suis to interact with lipid rafts on the surface of macrophages to be internalized, and the formed lipid rich phagosome is able to avoid fusion with lysosomes through this endocytic pathway. In addition, this furtive entry into macrophages does not affect the cell's normal trafficking. The smooth LPS also inhibits host cell apoptosis by O polysaccharides through a TNF alpha independent mechanism, which allows for B. suis to avoid the activation of the host immune system. by expressing metabolism genes mainly for amino acid synthesis. and the synthesis of DnaK chaperones. Nickel is essential for many enzymatic reactions, including ureolysis to produce ammonia which in turn may neutralize acidic pH. The Brucella abortus (rough LPS Brucella) vaccine, developed for bovine brucellosis and licensed by the USDA Animal Plant Health Inspection Service, has shown protection for some swine and is also effective against B. suis infection, but there is currently no approved vaccine for swine brucellosis.

In the United States, B. suis was the first biological agent weaponized in 1952, and was field tested with B. suis filled bombs called M33 cluster bombs. It is, however, considered to be one of the agents of lesser threat because many infections are asymptomatic and the mortality is low, but it is used more as an incapacitating agent.