BIOLOGICAL AND GENETIC-CHARACTERIZATION OF RICKETTSIA-SIBIRICA STRAINS ISOLATED IN THE ENDEMIC AREA OF THE NORTH ASIAN TICK TYPHUS

Restriction fragment length polymorphism (RFLP) analysis of polymerase chain reaction-amplified gene fragments was used to characterize 24 i solates of spotted fever group rickettsiae previously identified as Ri ckettsia sibirica from their serologic properties. These strains were obtained in Russia between 1946 and 1991 from humans and different spe cies of Ixodid ticks. The RFLP analysis was performed using amplified DNA products obtained with a genus-specific primer pair derived from t he R. prowazekii citrate synthase gene and two group-specific primer p airs from the R. rickettsii 190-kD and 120-kD surface protein antigen genes followed by Alu I, Pst I, and Rsa I restriction endonuclease dig estions. Although some differences were detected in biological charact eristics among the examined strains, only a single R. sibirica genotyp e was found with these molecular tools of identification.