Yersiniaspp. in Wild Rodents and Shrews in Finland

Abstract

Yersinia enterocolitica and Yersinia pseudotuberculosis are important zoonotic bacteria causing human enteric yersiniosis commonly reported in Europe. All Y. pseudotuberculosis strains are considered pathogenic, while Y. enterocolitica include both pathogenic and nonpathogenic strains which can be divided into six biotypes (1A, 1B, and 2-5) and about 30 serotypes. The most common types causing yersiniosis in Europe are Y. enterocolitica bioserotypes 4/O:3 and 2/O:9. Strains belonging to biotype 1A are considered as nonpathogenic because they are missing important virulence genes like the attachment-invasion-locus (ail) gene in the chromosome and the virulence plasmid. The role of wild small mammals as a reservoir of enteropathogenic Yersinia spp. is still obscure. In this study, the presence of Yersinia spp. was examined from 1840 wild small mammals, including voles, mice, and shrews, trapped in Finland during a 7-year period. We isolated seven Yersinia species. Y. enterocolitica was the most common species, isolated from 8% of the animals; while most of these isolates represented nonpathogenic biotype 1A, human pathogenic bioserotype 2/O:9 was also isolated from a field vole. Y. pseudotuberculosis of bioserotype 1/O:2 was isolated from two shrews. The ail gene, which is typically only found in the isolates of biotypes 1B and 2-5 associated with yersiniosis, was frequently (23%) detected in the nonpathogenic isolates of biotype 1A and sporadically (6%) in Yersinia kristensenii isolates. Our results suggest that wild small mammals, especially voles, may serve as carriers for ail-positive Y. enterocolitica 1A and Y. kristensenii. We also demonstrate that voles and shrews sporadically excrete pYV-positive Y. enterocolitica 2/O:9 and Y. pseudotuberculosis 1/O:2, respectively, in their feces and, thus, can serve as a contamination source for vegetables by contaminating the soil.

Identification of Yersinia at the Species and Subspecies Levels Is Challenging

“…For pathogenicity, pYV-encoded targets, such as yadA and virF, and chromosomal target genes ail and ystA are widely used (19,20,36,51,64). Species-specific regions of virulence genes have also been used for correct identification of enteropathogenic Yersinia (29). The new ISO method uses ail PCR to identify pathogenic Y. enterocolitica on selective agar plates before further confirmation (18).…”

“…The new ISO method uses ail PCR to identify pathogenic Y. enterocolitica on selective agar plates before further confirmation (18). However, ail has frequently been detected in Y. enterocolitica biotype 1A strains isolated from wildlife, but also recently in lettuce, and this gene should therefore not be used alone in PCR detection when searching for pathogenic strains (28,29,31). (Table 2).…”

Comparative genomic insights into Yersinia hibernica – a commonly misidentified Yersinia enterocolitica-like organism

“…hibernica isolates shows that all sequenced isolates share this deletion. Indeed, sucrose-negative Y. enterocolitica- like isolates have been reported from environmental sources [46] but without sequencing [8] and since the 16S rRNA gene for Y. enterocolitica and Y.…”

Yersinia pseudotuberculosis Prevalence and Diversity in Wild Boars in Northeast Germany

“…Improvement of the protocol for the cultural detection of Y. pseudotuberculosis. Although cold enrichment in conjunction with alkaline treatment (20 s in 0.25% or 0.5% potassium hydroxide [KOH] solution) has been used in several prevalence studies on Y. pseudotuberculosis (11,(25)(26)(27), some authors reported an increased susceptibility of this species to KOH (28)(29)(30). We analyzed the KOH susceptibility of seven strains belonging to five serotypes (O:1a, O:1b, O:3, O:4, and O:5), some of which are the most common serotypes in Europe (31).…”