16S rRNA sequences of Bartonella bacilliformis and cat scratch disease bacillus reveal phylogenetic relationships with the alpha-2 subgroup of the class Proteobacteria.

The primary structures of 16S rRNAs of Bartonella bacilliformis, an isolate of the cat scratch disease (CSD) bacillus, and a strain phenotypically similar to the CSD bacillus were determined by reverse transcriptase sequencing. These microorganisms were found to be members of the alpha-2 subgroup of the class Proteobacteria. The sequence from B. bacilliformis was most closely related to the rRNA of Rochalimaea quintana (91.7% homology), the etiologic agent of trench fever. The sequence from the isolate of the CSD bacillus showed the greatest homology with Brucella abortus (89.7%) and, when compared with oligonucleotide catalog data, formed a cluster with Rhodopseudomonas palustris, Pseudomonas carboxidovorans, Nitrobacter species, and Bradyrhizobium species. The 16S rRNA sequence was also determined for the Cleveland Clinic isolate, which was previously shown to be phenotypically similar to and approximately 30% related, by DNA hybridization, to the CSD bacillus. The Cleveland Clinic isolate was isolated from a patient not diagnosed with CSD. The rRNAs from these bacteria exhibited 98.2% homology, confirming that this isolate is a second species in the same genus as the CSD bacillus. Our data suggest that neither B. bacilliformis nor the CSD bacillus is the etiologic agent of bacillary epithelioid angiomatosis.