Rhodococcus Equi

Excerpt

Rhodococcus equi is a bacterium primarily associated with animals, particularly horses and foals, which are the natural hosts. Since 1967, significant cases of human infections have been reported with this rare bacterium, which was first identified by a young man working on immunosuppressant agents in a stockyard. Other Rhodococcus spp, including R fascias, R rhodochrous, and R erythropoiesis, are similarly described as human pathogens. Rhodococcus belongs to the Nocardiaceae family, which also comprises Nocardia, Mycobacterium, Corynebacterium, and Gordonia, exhibiting certain similarities among the group.

R equi is most accurately characterized as a soil organism present in the gastrointestinal tract of numerous herbivores and prevalent in animal dung, manures, soils of grazing fields, and other associated farm environments. Although R equi is considered a rare organism, it poses a specific risk to individuals with immunosuppressive conditions. Immunosuppression, especially defects in cell-mediated immunity, significantly contributes to the disease and is present in most reported cases. Individuals with weakened immune systems or immunocompromised conditions in which the infection has been described, including those undergoing chemotherapy, having HIV, leukemia, lymphoma, or lung cancer, those with prolonged steroid use, or those receiving monoclonal antibodies or solid organ or stem cell transplants, are susceptible to infections. R equi is a rare contributor to subacute, necrotizing pneumonia, resulting in cavitary pneumonia and lung abscesses. The condition predominantly causes pulmonary infections, ranging from simple pneumonia to necrotizing pneumonia and lung abscesses.