Characterization of the Natural Population of Bartonella henselae by Multilocus Sequence Typing

Abstract

Investigations of the population genetics of Bartonella henselae have demonstrated a high level of diversity among strains, and the delineation of isolates into one of two subtypes, type I (Houston) and type II (Marseille), represented by specific 16S ribosomal DNA (rDNA) sequences, has long been considered the most significant genotypic division within the species. This belief is challenged by recent work suggesting a role for horizontal gene exchange in generating intraspecies diversity. We attempted to resolve this issue and extend exploration of the population structure of B. henselae by using multilocus sequence typing (MLST) to examine the distribution of polymorphisms within nine different genes in a sample of 37 human and feline isolates. MLST distinguished seven sequence types (STs) that resolved into three distinct lineages, suggesting a clonal population structure for the species, and support for these divisions was obtained by macrorestriction analysis using pulsed-field gel electrophoresis. The distribution of STs among isolates recovered from human infections was not random, and such isolates were significantly more often associated with one particular ST, lending further support to the suggestion that specific genotypes contribute disproportionately to the disease burden in humans. All but one isolate lay on lineages that bore the representative strain of either the Houston or Marseille subtype. However, the distribution of the two 16S rDNA alleles among the isolates was not entirely congruent with their lineage allocations, indicating that this is not a sensitive marker of the clonal divisions within the species. The inheritances of several of the genes studied could not be reconciled with one another, providing further evidence of horizontal gene transfer among B. henselae strains and suggesting that recombination has a role in shaping the genetic character of bartonellae.Bartonella henselae is now well established as a significant human pathogen and is possibly the agent of the world's most common bacterial zoonosis acquired from a companion animal. The bacterium is naturally maintained through persistent, subclinical infections in felids and is transmitted between reservoir hosts via arthropods (Ctenocephalides felis). The prevalence of B. henselae bacteremia in domestic cats ranges from about 10 to 40% (7, 17), and infections have been encountered virtually worldwide. Cat scratch disease (CSD) is the most commonly encountered B. henselae-induced syndrome in humans, with an estimated 25,000 cases and several thousand hospitalizations occurring each year in the United States alone (16,19,21,34). B. henselae is also unique in its invasion mechanism (9) and capacity to drive angiogenesis in vitro and in vivo (20). Although the prevalence of reported CSD and other B. henselae infections is relatively high (10 cases per 100,000 population per annum in the United States), the frequency of human inoculation by B. henselae is likely to be considerably greater, given the high carriage rates in domestic...

Bartonella henselae exists as a mosaic of different genetic variants in the infected host

“…MLST was performed as previously described (Arvand et al, 2006;Iredell et al, 2003). In brief, the partial sequences of eight genetic loci, including 16S rRNA-DNA, batR, ftsZ, gltA, groEL, nlpD, ribC and rpoB, were analysed.…”

“…To test these hypotheses, 34 primary B. henselae isolates from different geographical regions were evaluated by PFGE analysis of multiple single-colonyderived cultures. The relationship among the genetic variants within a distinct isolate was further evaluated by multi-locus sequence typing (MLST), which has been shown to be an accurate method for the evaluation of genetic relatedness among B. henselae isolates (Arvand & Viezens, 2007;Iredell et al, 2003). In addition, 20 in vitrogenerated clones of B. henselae were subjected as singlecolony-derived cultures to PFGE analysis in order to determine whether genetic variants might also be detected within the progeny of in vitro-generated clones.…”

“…The DNA sequences were analysed by using the DNASTAR Lasergene. Alleles and sequence types (STs) were assigned in accordance with the published data (Arvand & Viezens, 2007;Iredell et al, 2003).…”

Simultaneous presence of two different copies of the 16S rRNA gene in Bartonella henselae

“…Subsequently, isolates belonging to the 16S RNA types I or II were detected by different investigators in other countries (Birtles et al, 2002;Chang et al, 2002; Drancourt et al, 1996; Guptill et al, 2004;Melter et al, 2003;Sander et al, 1997). The 16S RNA types were designated 16S RNA alleles 1 and 2 and included in the MLST scheme for B. henselae (Iredell et al, 2003).…”

“…Subsequently, isolates belonging to the 16S RNA types I or II were detected by different investigators in other countries (Birtles et al, 2002;Chang et al, 2002; Drancourt et al, 1996; Guptill et al, 2004;Melter et al, 2003;Sander et al, 1997). The 16S RNA types were designated 16S RNA alleles 1 and 2 and included in the MLST scheme for B. henselae (Iredell et al, 2003).We have recently studied the molecular epidemiology of B. henselae isolates from different hosts and various geographical regions by MLST (Arvand et al, 2007). During that study and in subsequent investigations, a total of 191 B. henselae isolates were subjected to direct 16S rRNA gene sequencing.…”