Septic arthritis due to Arcanobacterium haemolyticum.

Diphtheroids or "coryneform" bacilli are usually considered to be nonpathogenic "normal flora" of human skin and mucous membranes. Because bacterial cultures are frequently contaminated with these organisms the correct diagnosis and treatment may be delayed by the failure to recognize serious infections caused by them. Few confirmed cases of orthopaedic infections due to Arcanobacterium haemolyticum infection have been reported, partly because of inadequate identification of this bacterium. We report a case of septic arthritis due to A. haemolyticum.