Septic arthritis caused by Propionibacterium acnes.

The traditional view that Propionibacterium acnes is nonpathogenic for man, except as an agent associated with acne vulgaris, has been refuted. Propionibacterium acnes has been shown to cause endocarditis, meningitis, and other serious infections. We report a case of P acnes infection causing septic arthritis and contributing to a concurrent soft-tissue infection. This case supports and extends previous observations of the clinical importance of P acnes as a pathogen. A positive culture for P acnes cannot be uncritically dismissed as a bothersome contaminant without considering the clinical circumstances.