Genotypic Characteristics of Two Serotypes ofBartonella henselae

Abstract
The study of 16S rRNA gene sequences of all isolates ofBartonella henselaeobtained in our laboratory and others from human patients or cats has revealed two genotypes according to the sequence of the 16S rRNA gene. Two isolates of these genotypes have previously been related to two different serotypes, and lack of cross-protection of the two serotypes has been demonstrated in cats. We investigated the grouping of eight strains ofB. henselaeon the basis of 16S ribosomal DNA, 35-kDa protein, Pap 31 protein, and internal transcribed spacer (ITS) gene sequencing; sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) profiles; and monoclonal antibody reactivity studies. Houston-1, 90-615, and SA2 strains showed the same patterns in SDS-PAGE, but they differed from the patterns ofB. henselaeisolates URBHLLY8, URBHLIE9, Cat6, Fizz, and CAL-1. Nine monoclonal antibodies derived from BALB/c mice immunized withB. henselaeHouston-1 strain reacted only with strains Houston-1, 90-615, and SA2, and not with any otherBartonellastrains. The two serogroups corresponded with two genotypes based on differences in the sequences of the genes encoding 16S rRNA, 35-kDa protein, and Pap 31 protein. Sequences of ITS genes were highly divergent among strains, as each had a unique sequence and the subdivision was not supported by DNA-DNA relatedness study. Study of 22 additional strains ofB. henselaeisolated from French bacteremic cats demonstrated that they all belong to one or the other of the proposed serotype or genotype.