Evidence of Extensive Circulation of Yersinia enterocolitica in Rodents and Shrews in Natural Habitats from Retrospective and Perspective Studies in South Caucasus.

Yersinia enterocolitica culture-positive rodents and shrews were reported in different territories across Georgia during 14 of 17 years of investigations conducted for the period of 1981-1997. In total, Y. enterocolitica was isolated from 2052 rodents (15 species) and 33 shrews. Most isolates were obtained from Microtus arvalis, Rattus norvegicus, Mus musculus, and Apodemus spp. During the prospective study (2017-2019), isolates of Yersinia-like bacteria were cultured from 53 rodents collected in four parts of Georgia. All the Yersinia-like isolates were confirmed as Y. enterocolitica based on the API 20E and the BD Phenix50 tests. Whole-genome (WG) sequencing of five rodents and one shrew strain of Y. enterocolitica revealed that they possessed a set of virulence genes characteristic of the potentially pathogenic strains of biogroup 1A. All isolates lacked distinguished virulence determinants for YstA, Ail, TccC, VirF, and virulence plasmid pYV but carried the genes for YstB, YmoA, HemPR-HmuVSTU, YaxAB, PhlA, PldA, ArsCBR, and a flagellar apparatus. One strain contained a gene highly homologous to heat-labile enterotoxin, a chain of E. coli, a function not previously described for Y. enterocolitica. The WG single-nucleotide polymorphism-based typing placed the isolates in four distinct phylogenetic clusters.

Identification of a Novel Yersinia enterocolitica Strain from Bats in Association with a Bat Die-Off That Occurred in Georgia (Caucasus).

Yersinia entercolitica is a bacterial species within the genus Yersinia, mostly known as a human enteric pathogen, but also recognized as a zoonotic agent widespread in domestic pigs. Findings of this bacterium in wild animals are very limited. The current report presents results of the identification of cultures of Y. entercolitica from dead bats after a massive bat die-off in a cave in western Georgia. The growth of bacterial colonies morphologically suspected as Yersinia was observed from three intestine tissues of 11 bats belonging to the Miniopterus schreibersii species. These three isolates were identified as Y. enterocolitica based on the API29 assay. No growth of Brucella or Francisella bacteria was observed from tissues of dead bats. Full genomes (a size between 4.6-4.7 Mbp) of the Yersinia strains isolated from bats were analyzed. The phylogenetic sequence analyses of the genomes demonstrated that all strains were nearly identical and formed a distinct cluster with the closest similarity to the environmental isolate O:36/1A. The bat isolates represent low-pathogenicity Biotype 1A strains lacking the genes for the Ail, Yst-a, Ysa, and virulence plasmid pYV, while containing the genes for Inv, YstB, and MyfA. Further characterization of the novel strains cultured from bats can provide a clue for the determination of the pathogenic properties of those strains.