Persistence of rickettsiae in the partially viable gangrenous margins of amputated extremities 5 to 7 weeks after onset of rocky mountain spotted fever

A case of Rocky Mountain spotted fever complicated by gangrene of the extremities required amputation and showed persistent rickettsial infection in the margins of the gangrene at 5 and 7 weeks after onset of illness. Rickettsial organisms were demonstrated by immunoperoxidase staining in the viable endothelial cells in the ischemic margins of the gangrenous tissue. We conclude that the cellular, humoral, and pharmacologic components that lead to eradication of the rickettsiae were not delivered to the ischemic margins at effective antirickettsial concentrations.