Isolation of Entamoeba histolytica from arthritic knee joint.

Amoebae were isolated from an arthritic knee of a male patient. The organisms grew in Egg Yolk Infusion medium, and in Diamond's Biosate Iron-Serum-33 medium, which contained Trypanosoma cruzi, and were identified microscopically as Entamoeba histolytica. Furthermore, amoebae-like organisms in aspirate and cultures were immunocytochemically identified using monoclonal antibodies against E. histolytica. On the basis of the morphologic and immunologic observations, it was concluded that the knee lesion was caused by infection with E. hystolytica. The knee lesion resolved following treatment with metronidazole. This case is the first report of an amoebic infection of the knee joint.