Characterization of a Yersinia enterocolitica biotype 1A strain harbouring an ail gene

Abstract

Aims: The chromosomal ail gene (attachment and invasion locus) is commonly used as target gene for the detection of pathogenic Y. enterocolitica strains in food testing. The ail PCR does not detect strains of biotype 1A (BT1A), which are regarded as non‐pathogenic because BT1A strains lack the virulence plasmid and chromosomally encoded virulence genes. In some recent reports, however, BT1A strains were discovered that harboured the ail gene. We isolated an ail‐positive strain and characterized this strain with phenotypic and genotypic methods to study its possible relation to pathogenic Y. enterocolitica strains. Methods and Results: The ail region of the BT1A strain was sequenced and compared with the corresponding region of nonpathogenic BT1A strains and pathogenic strains. Pulsed field gel electrophoresis (PFGE) analysis was applied revealing no similarity of the PFGE pattern of this strain to the patterns of pathogenic strains. Virulence‐gene‐based PCR analyses showed the strain to be positive for ystB, but negative for virulence genes ystA, virF and yadA. Whole‐cell MALDI‐TOF MS combined with a shrinkage discriminant analysis approach was applied and clearly classified the ail‐positive biotype 1A strain within the cluster of BT1A strains. Conclusions: PCR detection of ail sequences in food matrices should be followed by the isolation of the responsible strain and its characterization using phenotypic or genotypic methods. Significance and Impact of the Study: The ail gene may be present in Y. enterocolitica BT1A strains, which are commonly considered as nonpathogenic. Efficient methods such as PCR typing of other virulence genes or rapid MALDI‐TOF MS‐based bacterial profiling allow a more comprehensive assessment of the pathogenicity potential of Yersinia strains.

Microbiological survey of raw and ready-to-eat leafy green vegetables marketed in Italy

“…One of these was validated in house and used during this monitoring programme (Mäde et al, 2008). The results of this study confirmed that the use of RT-PCR is a very useful tool for detecting only pathogenic bio(sero)types of Y. enterocolitica in food (Kraushaar et al, 2011;Miller et al, 1989).…”

Low prevalence of human enteropathogenic Yersinia spp. in brown rats (Rattus norvegicus) in Flanders

“…However, the increasing isolation of this biotype from clinical cases draws more attention to BT1A [3;22]. Although rare, the presence of the ail- gene has previously been demonstrated in BT1A isolates [20;27]. The presence of the enterotoxin-gene ystB in combination with the ail- virulence gene could be an indication that these BT1A strains possess virulent characteristics [30].…”

“…The presence of the enterotoxin-gene ystB in combination with the ail- virulence gene could be an indication that these BT1A strains possess virulent characteristics [30]. However, potential loss of gene function, related to horizontal gene transfer cannot be ruled out [20]. The high genotypic diversity of BT1A makes the classification in clinical and non-clinical isolates more problematic since other, yet unknown, virulence factors could be contributing to the observed virulence in some strains [3;22;31].…”

Yersinia enterocolitica Isolates from Wild Boars Hunted in Lower Saxony, Germany

“…2). The ail gene is often used to differentiate pathogenic from nonpathogenic Yersinia strains, even though ailpositive BT 1A isolates were recently reported, leading to the conclusion that methods which are exclusively based on the detection of ail genes are insufficient to distinguish between pathogenic and nonpathogenic strains (17,44,45). In contrast to our results, 14 out of 17 enteropathogenic Yersinia isolates recovered from wild boars shot between 2007 and 2008 in Switzerland were identified to be Y. enterocolitica and carriers of the chromosomal virulence gene marker ail (19).…”