Diagnosing Rickettsia: Crimps, Complications, and

by Denison et al [1] conducted a study on the detection of the 3 most common spotted fever group rickettsia (SFGR) species endemic to the United States: Ricksettsia rickettsii, Rickettsia parkeri, and Rickettsia akari. When patients present with fever and rash and SFGR is in the diagnosis, serology and skin biopsy are often done. Serology can be negative early, so skin biopsies are performed. Both immunohistochemical stain (IHC) and nested polymerase chain reaction (PCR) remain the standard tests. There are potential problems with IHC in a skin biopsy: (1) The rickettsial antigen