Corynebacterium equi: a review of 12 cases of human infection.

Corynebacterium equi, an aerobic, variably acid-fast, gram-positive "diphtheroid," is an unusual cause of pulmonary infection in immunosuppressed patients. Initially, infection with C. equi may be mistaken for a mycobacterial infection. Two cases in a two-year period were observed and compared with the 10 cases previously reported in the literature. All but one patient had pulmonary involvement, and the presentation of all other patients was typically insidious, with fatigue, fever, and nonproductive cough. Chest roentgenograms showed cavitary lesions in seven of 11 patients. Four of 12 patients had associated bacteremias, and three of 12 had subcutaneous abscesses or lymphadenitis. One of our patients developed multiple brain abscesses. Overall mortality was 25%. The organism is susceptible to vancomycin, erythromycin, aminoglycosides, and chloramphenicol. Optimal duration of antibiotic therapy and the proper role of surgery in treatment is uncertain, but relapses have been common and many weeks of antibiotic therapy have generally been required for cure.