Rhodococcus equi infection: a cause of cavitary pulmonary disease in immuno-compromised patients.

Rhodococcus equi is a facultatively-aerobic, gram-positive and intracellular bacteria that causes pulmonary and disseminated infections in immuno-compromised patients. It is a common agent that causes pneumonia in farm animals and only rarely is transmitted to man. I report a case of pneumonia caused by this agent in a patient with AIDS who had been misdiagnosed as tuberculosis and treated as such for five months before the correct diagnosis was made. The diagnosis should be suspected on clinical and radiologic grounds as treatment is considerably different from other opportunistic pathogens in AIDS.