Rhodococcus equi cavitary pneumonia in HIV-infected patients: an unsuspected opportunistic pathogen.

Two patients seropositive for human immunodeficiency virus (HIV) and with no previous acquired immunodeficiency syndrome-defining conditions developed cavitary pneumonia and pleural disease caused by Rhodococcus equi. R. equi was isolated from these patients' sputum and lung biopsy specimens, respectively, but the microorganism was initially considered to be a contaminant (patient 1) or misidentified as a nontuberculous mycobacterium (patient 2). The R. equi infection was fatal in one patient, who died after 4 months without specific antimicrobial therapy; the second patient was unresponsive to combination therapy with various antimicrobial agents. R. equi may cause life-threatening infections in HIV-infected patients. Microbiology laboratories should be cognizant of the need to exclude R. equi as a cause of infection in highly immunosuppressed patients.