Genomic Study ofRickettsia akariby Pulsed-Field Gel Electrophoresis

Pulsed-field gel electrophoresis ofSmaI-,EagI-, andBssHII-digested DNA was used to perform restriction fragment length polymorphism analysis ofRickettsia akaristrains isolated from humans, rodents, and mites in the United States and Ukraine. Although some differences in biological and serological characteristics were present between strains, the genomic studies demonstrated a high degree of intraspecies homogeneity of R. akari isolates. Our results confirm the value of pulsed-field gel electrophoresis‐restriction fragment length polymorphism analysis for the identification of species of rickettsiae. Rickettsia akari is an obligate gram-negative intracellular bacterium that causes rickettsialpox in humans (11, 19, 20). Domestic mice and gray rats are natural reservoirs of these bacteria, which are transmitted to humans by the bite of the mite Allodermanyssus (Liponyssoides) sanguineus (11, 19, 20). Rickettsialpox is a mild disease characterized by an eschar-like lesion at the site of the mite bite, fever, headache, lymphadenopathy with leukopenia, and a papulovesicular rash (11, 16). While outbreaks of rickettsialpox were reported in the United States (11) and Ukraine (16, 20) in the 1940s and 1950s, only sporadiccaseshavebeenreportedsincethen.R.akarihasbeen isolated from voles in Korea (12), although disease in humans has not been reported. Serological surveys have been performed to determine the prevalence of R. akari infections in humans in the Balkan countries, Italy, Costa Rica, and Africa (16) and indicated that R. akari might have a worldwide distribution. Recent reports of human rickettsialpox in Croatia (14) and 13 clinical cases from New York City (13) indicate that infections withR. akariare still prevalent.