Propionibacterium acnes cerebral botryomycosis. The role of plastic embedding in the diagnosis of grain-producing infections.

Botryomycosis is a chronic infection in which bacterial colonies, or "grains," occur in purulent exudate associated with draining sinus tracts or abscess formation. This condition usually is caused by Staphylococcus and Streptococcus, but other organisms occasionally have been implicated. This report describes the first case of botryomycosis caused by Propionibacterium acnes, a diphtheroid that has been rarely associated with opportunistic disease. In this case, plastic embedding allowed the observation of the structural details of the organisms composing the grains and permitted their presumptive identification as diphtheroids. The differential diagnosis of infectious agents that produce grains in tissue sections also will be discussed.