Arthritis caused by Corynebacterium striatum: spontaneous infection?

I read with interest the case report by David Scholle of arthritis caused by Corynebacterium striatum (1). The author concluded that the knee joint was most likely infected hematogenously and was, thus, a case of “a spontaneous infection of a natural joint.” However, the patient initially presented with a painful knee following trauma for which he underwent a diagnostic aspiration. This aspirate was culture negative; however, 20 days later, the knee joint was again aspirated because of persistent pain and swelling, and the aspirate now showed many neutrophils and a pure culture of Corynebacterium striatum. Although infection is a rare complication of intra-articular injection and may be even more rare after diagnostic needle aspiration of a joint, I would certainly consider this infection with C. striatum to be iatrogenic, with the introduction of this skin commensal organism into the joint during the first aspiration (2).