Rhodococcus equi is a Gram-positive bacterium. The organism is commonly found in dry and dusty soil and can be important for diseases of domesticated animals (horses and goats). The frequency of infection can reach near 60%. R. equi is an important pathogen causing pneumonia in foals. Since 2008, R. equi has been known to infect wild boar and domestic pigs.
R. equi can infect humans. At-risk groups are immunocompromised people, such as HIV-AIDS patients or transplant recipients. Rhodococcus infection in these patients resemble clinical and pathological signs of pulmonary tuberculosis.