Genetic Analysis of Isolates of the Spotted Fever Group of Rickettsiae Belonging to the R. Conorii Complex

The cytoplasmic 120 kDa antigen genes of 9 isolates of Rickettsia conorii (RC), 12 isolates of R. africae (RA), and 3 isolates of Israeli tick typhus rickettsiae (ISTT) were compared for restriction fragment length polymorphisms (RFLP) present in portions of the open reading frame amplified by polymerase chain reaction (PCR). Initially, DNAs from 13 species or serotypes of spotted fever group rickettsiae were used to select restriction enzymes (RE) that detected RFLP in gene fragments amplified with primer pairs 483WF/1514R and 764F/3409R. Among the R. conorii complex isolates, Dpn II gave RFLP differentiating all three serotypes. Unique RE patterns were obtained for RC with Bsr I and Hinf I, for RA with Mwo I, Pst I and Ssp I, and for ISTT with Hpa II. While RFLP typing of the 120 kDa gene permitted rapid separation of R. conorii complex isolates into three groups corresponding to the RC, RA, and ISTT rOmp serotypes, additional intragroup genetic variation was also detected in all three serotypes.