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Updated: Jun 13, 2026

An Electroporation Method to Transform Rickettsia spp. with a Fluorescent Protein-Expressing Shuttle Vector in Tick Cell Lines
Published on: October 11, 2022
The expanding spectrum of eschar-associated rickettsioses in the United States
W Chad Cragun1, Brenda L Bartlett, Michael W Ellis
1Dermatology Service, San Antonio Military Medical Center, 2200 Bergquist Dr, Ste 1, Lackland AFB, TX 78236-9908, USA. chad.cragun@us.army.mil
Background:
Until recently, Rickettsia rickettsii was the only substantiated cause of tick-borne spotted fever group (SFG) rickettsiosis in humans in the United States. Rickettsia parkeri, originally thought to be nonpathogenic in humans, was recently proved to be another cause of tick-borne SFG rickettsiosis.
Observations:
We report 3 cases of SFG rickettsiosis and discuss the epidemiology, clinical presentation, histopathologic features, and laboratory findings that support confirmed or probable diagnoses of R parkeri infection and describe the expanding list of eschar-associated SFG rickettsioses recognized in US patients.
Conclusions:
The SFG rickettsioses share many clinical manifestations and extensive antigenic cross-reactivity that may hamper specific confirmation of the causative agent.
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