Nocardia farcinica arthritis of the knee. A case report.

Nocardia is a gram positive, aerobic branched actinomycete; it is an ubiquitous soil saprophyte. As an infecting agent it has been increasingly identified in humans, especially in immuno-suppressed hosts. Nocardia as a cause of septic arthritis is very unusual. The described genus was Nocardia asteroides in nearly all previously reported cases. We report an unusual case of spontaneous Nocardia farcinica septic arthritis of the left knee in a 68-year-old man, who was under systemic corticosteroids for chronic obstructive pulmonary disease. The diagnosis was rapidly made by Gram and acid-fast stains and later confirmed by culture. PCR was used to identify the subtype. The patient was treated successfully with sulphametaxazole-trimethoprim for six months. Our case re-emphasises, especially in the immuno-compromised patient, the importance of performing fungal and acid-fast bacilli cultures, besides the most common bacterial cultures for aerobic and anaerobic organisms, in order to identify less common organisms and to initiate early and adequate treatment.