Insights into the individual evolutionary origins of Yersinia virulence factor effector proteins.

Pathogenic Yersinia bacteria, including Y. pseudotubuclosis Y. enterocolitica, and Y. pestis, contain the mosaic plasmid pYV that encodes for, among other things, a number of proteinaceous virulence factors. While the evolutionary histories of many of the biovars and strains of pathogenic Yersinia species are well documented, the origins of many of the individual virulence factors have not been comprehensively examined. Here, the evolutionary origins of the genes coding for a set of Yersinia outer protein (Yop) virulence factors were investigated through phylogenetic reconstruction and subsequence analysis. It was found that many of these genes had only a few sequenced homologs and none of the resolved phylogenies recovered the same relationships as was resolved from chromosomal analyses. Many of the evolutionary relationships differ greatly among genes on the plasmid, and variation is also found across different domains of the same gene, which provides evidence of the mosaic nature of the plasmid as well as multiple genes on the plasmid. This mosaic aspect also relates to patterns of selection, which vary among the studied domains.

Antimicrobial resistance of Yersinia enterocolitica and presence of plasmid pYV virulence genes in human and animal isolates.

Interactions between bacterial virulence and antimicrobial resistance are of increasing interest in clinical microbiology. On this account, antimicrobial resistance of Yersinia enterocolitica O:3 strains isolated from humans (n = 55), food-chain animals (n = 58) and companion animals (n = 13) was determined in relation to the absence or presence of the pYV plasmid-encoded virulence genes yadA and virF. There were no statistically significant associations between the rate of antimicrobial resistance and the presence or absence of the plasmid, in either human-derived or animal-derived strains. Therefore, it can be concluded that response to conventionally used antimicrobials in Y. enterocolitica O:3 strains is not dependent on pYV-encoded virulence determinants.