Yersinia enterocolitica, an important food- and water-borne enteric pathogen, is represented by six biovars viz. 1A, 1B and 2-5. Some biovar 1A strains, despite lacking virulence plasmid (pYV) and chromosomal virulence genes, have been reported to cause symptoms similar to that produced by isolates belonging to known pathogenic biovars. Virulence-associated genes viz. ail, virF, inv, myfA, ystA, ystB, ystC, tccC, hreP, fepA, fepD, fes, ymoA and sat were studied in 81 clinical and nonclinical strains of Y. enterocolitica biovar 1A by PCR amplification. All strains lacked ail, virF, ystA and ystC genes. The distribution of other genes with respect to clonal groups revealed that four genes viz. ystB, hreP, myfA and sat were associated exclusively with strains belonging to clonal group A. The clonal groups A and B were differentiated previously based on rep (REP-/ERIC) - PCR genomic fingerprinting. The distribution of virulence-associated genes, however, did not differ significantly between clinical and nonclinical strains. In strains of Y. enterocolitica biovar 1A, clonal groups seem to reflect virulence potential better than the source (clinical vs. nonclinical) of isolation.

Yersinia enterocolitica is a gastrointestinal pathogen which causes yersiniosis, an illness characterized by diarrhea, ileitis, and mesenteric lymphadenitis. Y. enterocolitica is transmitted via the feco-oral route by the consumption of contaminated food or water. Several phenotypic and genotypic methods have been developed to reliably detect Y. enterocolitica in food. However, the source of infection of many recently reported foodborne outbreaks remains obscure. The detection of this pathogen in food is a challenging task, since it shares similarities with other enteric bacteria. The presence of other microorganisms in the food samples makes it even more difficult to identify this slow-growing pathogen. Therefore, the present-day emphasis is on the development of sensitive, easily automated methods suitable for in-situ detection, allowing quick and cost-effective characterization of food samples. This review summarizes and compares the currently available cultural, immunological, and molecular methods, particularly in relation to their specific merits or demerits when implemented for the detection of Y. enterocolitica in food.

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Yersinia enterocolitica, an important food- and water-borne enteropathogen causes acute diarrhea, terminal ileitis, and mesenteric lymphadenitis. It is represented by six biovars (1A, 1B, 2-5). The biovar 1A strains are generally regarded as avirulent as they lack pYV plasmid and major chromosomal virulence genes. Despite this, some biovar 1A strains produce disease symptoms indistinguishable from that produced by known pathogenic biovars (1B, 2-5). Suggested prospective studies to understand pathogenic potential of biovar 1A should focus on role of insecticidal toxins, urease, protease, superoxide dismutase, and host responses. These studies should also take into account the clonal groups of biovar 1A.

BackgroundYersinia enterocolitica, an important food- and water-borne enteric pathogen is represented by six biovars viz. 1A, 1B, 2, 3, 4 and 5. Despite the lack of recognized virulence determinants, some biovar 1A strains have been reported to produce disease symptoms resembling that produced by known pathogenic biovars (1B, 2-5). It is therefore imperative to identify determinants that might contribute to the pathogenicity of Y. enterocolitica biovar 1A strains. Y. enterocolitica invariably produces urease and the role of this enzyme in the virulence of biovar 1B and biovar 4 strains has been reported recently. The objective of this work was to study genetic organization of the urease (ure) gene complex of Y. enterocolitica biovar 1A, biochemical characterization of the urease, and the survival of these strains under acidic conditions in vitro.ResultsThe ure gene complex (ureABCEFGD) of Y. enterocolitica biovar 1A included three structural and four accessory genes, which were contiguous and was flanked by a urea transport (yut) gene on the 3' side. Differences were identified in ure gene complex of biovar 1A strain compared to biovar 1B and 4 strains. This included a smaller ureB gene and larger intergenic regions between the structural genes. The crude urease preparation exhibited optimal pH and temperature of 5.5 and 65°C respectively, and Michaelis-Menten kinetics with a Km of 1.7 ± 0.4 mM urea and Vmax of 7.29 ± 0.42 μmol of ammonia released/min/mg protein. The urease activity was dependent on growth temperature and growth phase of Y. enterocolitica biovar 1A, and the presence of nickel in the medium. The molecular mass of the enzyme was > 545 kDa and an isoelectric point of 5.2. The number of viable Y. enterocolitica biovar 1A decreased significantly when incubated at pH 2.5 for 2 h. However, no such decrease was observed at this pH in the presence of urea.ConclusionsThe ure gene cluster of biovar 1A strains though similar to biovar 1B and 4 strains, exhibited important differences. The study also showed the ability of biovar 1A strains of Y. enterocolitica to survive at highly acidic pH in vitro in the presence of urea.