B. suis

An overview of Brucella suis, a bacterial species causing brucellosis in pigs and humans

Brucella suis is a Gram-negative, facultative intracellular bacterium that is one of the causative agents of brucellosis. It primarily affects pigs, but it can also infect humans, leading to a zoonotic disease. B. suis is of significant concern in veterinary and human medicine due to its impact on animal health and its potential to cause serious illness in humans.

Taxonomy and Classification

Brucella suis belongs to the genus Brucella, which is part of the family Brucellaceae. The genus Brucella includes several species that are pathogenic to various animals and humans. B. suis is further divided into five biovars, each with varying host preferences and geographical distributions.

Morphology and Physiology

Brucella suis is a small, non-motile, coccobacillus. It is an aerobic organism that does not form spores. The bacterium is characterized by its ability to survive and replicate within host cells, particularly macrophages, which allows it to evade the host's immune system.

Pathogenesis

Brucella suis enters the host through mucosal surfaces, often via ingestion or inhalation. Once inside the host, it is phagocytosed by macrophages and other cells of the reticuloendothelial system. The bacterium can survive and replicate within these cells by inhibiting phagosome-lysosome fusion, thus avoiding destruction.

Clinical Manifestations

In pigs, B. suis infection can lead to reproductive failure, including abortion, infertility, and orchitis. In humans, the disease manifests as undulant fever, fatigue, joint pain, and other systemic symptoms. Chronic infection can lead to more severe complications such as endocarditis and osteomyelitis.

Diagnosis

Diagnosis of Brucella suis infection involves a combination of serological tests, culture techniques, and molecular methods such as PCR. Serological tests detect antibodies against Brucella antigens, while culture and PCR can confirm the presence of the bacterium.

Treatment

Treatment of B. suis infection in humans typically involves a combination of antibiotics, such as doxycycline and rifampin, over an extended period to prevent relapse. In animals, control measures focus on biosecurity, vaccination, and culling of infected individuals.

Prevention and Control

Preventive measures include vaccination of livestock, biosecurity practices to prevent the spread of infection, and public health education to reduce the risk of zoonotic transmission. In endemic areas, control programs aim to reduce the prevalence of infection in animal populations.

Also see

• Brucellosis
• Brucella abortus
• Zoonosis
• Infectious disease