Genetic classification of "Rickettsia heilongjiangii" and "Rickettsia hulinii," two Chinese spotted fever group rickettsiae

To determine the phylogenetic position of two new rickettsial strains isola ted from ticks in China, 168 ribosomal DNA, gltA, and ompA (apart from the tandem repeat units) genes were amplified by PCR and sequenced. The phyloge netic relationships between these strains and other rickettsiae were inferr ed from the comparison of sequences of the three genes by the parsimony, ne ighbor-joining, and maximum-likelihood methods. The results demonstrated th at the 054 strain, a rickettsia pathogenic in humans, and the HL-93 strain were related and clustered together with Rickettsia japonica. Significant s tatistical bootstrap values (100 and 92%) supported the nodes in this clust er. Based on previous genotypic and antigenic data and the phylogenetic ana lysis presented here, the 054 and HL-93 strains should be considered as new species, and we formally propose that they be named "Rickettsia heilongjia ngii" and "Rickettsia hulinii," respectively.