Identification of Bartonella bacilliformis genotypes and their relevance to epidemiological investigations of human bartonellosis.

Genotypic diversity among 26 isolates of Bartonella bacilliformis obtained from different areas of Peru, and at different times, was assessed by comparison of DNA sequences derived from 16S-23S ribosomal DNA intergenic spacer regions (ISR) and a citrate synthase gene (gltA) fragment and by amplified fragment length polymorphism (AFLP) analysis. gltA comparison divided the isolates into two groups, whereas ISR comparison revealed six sequences. AFLP analysis using a selective primer delineated five profiles that correlated well with those obtained by sequence comparison. Combination of all three data sets divided the isolates into six genotypes. One of these genotypes was common to isolates collected from a large area in western Peru that corresponded to the region of endemicity for bartonellosis; however, isolates belonging to two other genotypes were also found within this region. Two of these genotypes were found in isolates isolated more than 35 years apart. The remaining three genotypes were each specifically associated with three outbreaks of bartonellosis that have recently occurred in areas where the disease had not previously been recognized. Demonstration of the unique nature of these isolates indicates that the outbreaks with which they were associated did not result from the introduction of disease by individuals who acquired their infection in the recognized region of endemicity. The sources of these outbreaks remain unknown. A consensus approach to bacterial typing using comparative sequence analysis of multiple genetic loci and the pan-genomic sampling of AFLP appears to offer a well-supported assessment of B. bacilliformis diversity, and the genotypic differences identified appear to have epidemiological significance.