Prompt confirmation of Rocky Mountain spotted fever: identification of rickettsiae in skin tissues.

Rickettsia rickettsii were identifiable by the immunofluorescence technique in skin specimens obtained by biopsy on days 4 and 8 of illness from patients with Rocky Mountain spotted fever. The immunofluorescence technique is regarded as a practical means of confirming the diagnosis during the early stages of illness before positive serologic reactions can be obtained.