About Bartonella Henselae

Bartonella henselae, is a Gram-negative, fastidious bacterium associated with cats. B. henselae infection in cats is usually asymptomatic, but infected cats may remain bacteremic for long periods, thus playing a major role as a reservoir for the bacterium. Transmission of B. henselae among cats is mediated by the cat flea, Ctenocephalides felis. Human infection occurs through cat scratches or bites and presents as cat scratch disease, bacillary angiomatosis, peliosis hepatis, endocarditis, or a variety of other, less frequent, manifestations.

Although criteria exist to classify Bartonella isolates as new species or not, there is a need for a method able to reliably identify B. henselae at the strain level. Such a method would allow investigating whether epidemic strains occur in cats, the geographic heterogeneity of B. henselae isolates, and the relationships between cat and human isolates. Various typing methods have been proposed for typing Bartonella isolates. Among these, DNA fingerprinting methods such as pulsed field gel electrophoresis, enterobacterial repetitive intergenic consensus (ERIC)-PCR, repetitive extragenic palindromic (REP)-PCR, or infrequent restriction site (IRS)-PCR, require large amounts of DNA, and/or are hardly reproducible and comparable among laboratories. In contrast, sequence-based methods have the advantages of being applicable to clinical or environmental specimens, and to produce reproducible and comparable results. Several target genes have been used for subtyping B. henselae. 16S rDNA classified B. henselae isolates into two main genotypes, i.e., types I and II, and was first considered as a useful delineation among isolates because the two genotypes also exhibited different serotypes and possessed consistently distinguishable protein profiles. Sequences from the ftsZ, gltA, 35-kDa protein-encoding, groEL and pap31 genes, and from the 16S-23S intergenic spacer, later permitted the identification of 3, 2, 2, 4, and 6 genotypes, respectively, that did not exactly match 16S rDNA types. However, to date, the most discriminatory typing method for B. henselae is multi-locus sequence typing (MLST) incorporating 9 genes. This method distinguished 7 genotypes among 37 human and cat isolates, and suggested that lateral gene transfer occurs among B. henselae isolates. Although these investigators and others suggested that human infection is caused by a limited number of specific B. henselae genotypes, the discriminatory power of the genotyping methods they used, and the small number of B. henselae isolates they studied, were insufficient to allow any statistically-significant conclusions to be drawn.

MST using the nine most variable spacer sequences between the B. quintana and B. henselae genomes identified 39 genotypes among 126 tested cat isolates. The MST classification matched the phylogenetic organization of cat isolates. MST is the mot discriminatory genotyping method to date for B. henselae.

Publication

• 2006-07-01Multispacer typing to study the genotypic distribution of Bartonella henselae populationsLi W, Chomel BB, Maruyama S, Guptil L, Sander A, Raoult D, Fournier PE
• 2007-08-01Genetic diversity of Bartonella henselae in human infection detected with multispacer typingLi W, Raoult D, Fournier PE