Yersinia enterocolitica is the causative agent of yersiniosis, a zoonotic disease of growing epidemiological importance with significant consequences for public health. This pathogenic species has been intensively studied for many years. Six biotypes (1A, 1B, 2, 3, 4, 5) and more than 70 serotypes of Y. enterocolitica have been identified to date. The biotypes of Y. enterocolitica are divided according to their pathogenic properties: the non-pathogenic biotype 1A, weakly pathogenic biotypes 2–5, and the highly pathogenic biotype 1B. Due to the complex pathogenesis of yersiniosis, further research is needed to expand our knowledge of the molecular mechanisms involved in the infection process and the clinical course of the disease. Many factors, both plasmid and chromosomal, significantly influence these processes. The aim of this study was to present the most important virulence markers of Y. enterocolitica and their role during infection.

Y. enterocolitica is the causative agent of yersiniosis - a foodborne zoonosis with substantial importance to public health. Y. enterocolitica is widespread in the environment and animal populations, posing a potential source of infection to humans. Presentation of yersiniosis as a zoonotic foodborne disease of relevance to public health. State of knowledge. Swine play an important role as a reservoir of Y. enterocolitica and insufficiently thermally processed pork is the main source of infection to humans. The correlation between strains isolated from pigs and from clinical cases of human yersiniosis has been sufficiently proven. Yersiniosis usually appears with gastrointestinal disturbances in children, whereas in adults it manifests in a pseudo-appendix form. The extra-enteric form of yersiniosis is rare. Classical bacteriological methods used for classifying Y. enterocolitica as pathogenic does not take into account the new aspects of the pathogenesis of yersiniosis. The examples are biotype 1A strains, commonly regarded as non-pathogenic, although they are increasingly often isolated from clinical cases of yersiniosis. Molecular methods seem much more effective and accurate in the diagnostic. New diagnostic tools such as real-time PCR, allows not only qualitative examination, but also quantitative evaluation of genes expression level, or single nucleotide polymorphism detection. Yersiniosis is an important food-borne zoonosis with wide range of clinical symptoms. Considering the fact that pork is the main source of infection for humans, public information campaigns seems to be an important element of the preventive measures against Y. enterocolitica infections.

Natural reservoirs of Yersinia (Y.) enterocolitica comprise different animal species, but little is known about the role of wild animals in the epidemiology of yersiniosis. The aim of the study was to evaluate the prevalence of Y. enterocolitica among game animals in Poland. The bio-serotypes and the pathogenicity markers of the analyzed isolates were determined. The experimental material comprised rectal swabs from 857 free-living animals hunter-harvested over a period of 2 years (2013–2014) in hunting districts across Poland. The isolates from bacteriological studies were confirmed by PCR and bio-serotyped based on the results of biochemical and agglutination tests. In the group of the 218 analyzed isolates of Y. enterocolitica, 133 were derived from wild boars, 70 from red deer, 11 from roe deer and 4 from fallow deer, and they accounted for 61.0%, 32.1%, 5.1% and 1.8% of all isolates, respectively. Bio-serotyping assays revealed that 91.7% of the examined isolates belonged to biotype 1A (200/218). The remaining 18 isolates belonged to bio-serotypes 1B/NI (3/218, 1.4%), 1B/O:8 (1/218, 0.5%), 2/NI (6/218, 2.8%), 2/O:27 (1/218, 0.5%), 2/O:3 (1/218, 0.5%), 2/O:9 (2/218, 0.9%), 3/NI (2/218, 0.9%), 4/O:3 (1/218, 0.5%) and 4/O:9 (1/218, 0.5%). The ail gene, a suggestive virulence gene for Y. enterocolitica, has been found in 30 isolates from 20 wild boars, in 6 isolates from red deer, and in 1 isolate from roe deer. Our study demonstrated that Y. enterocolitica is frequently isolated from game animals in Poland, which poses a risk of spreading these infectious agents to other animal species and humans.

SUMMARY: The objective of this study was to identify the bioserotypes and virulence markers ofYersinia enterocoliticastrains isolated from wild boars in Poland. Bacteriological examination of 302 rectal swabs from 151 wild boars resulted in the isolation of 40Y. enterocoliticastrains. The majority of the examined strains (n= 30), belonged to bioserotype 1A/NI. The presence of individualY. enterocoliticastrains belonging to bioserotypes 1B/NI (3), 1A/O:8 (2), 1A/O:27 (2), 2/NI (1), 2/O:9 (1) and 4/O:3 (1) was also demonstrated. Amplicons corresponding toailandystAgenes were observed only in oneY. enterocoliticastrain – bioserotype 4/O:3. TheailandystBgene amplicons were noted in 11Y. enterocoliticabiotype 1A strains, although single amplicons ofystBgene were found in 28 of the tested samples. In four out of eight cases when twoY. enterocoliticastrains were isolated from the same animal, the strains differed in biotype, serotype or virulence markers. The European population of wild boars continues to grow and spread to new areas, therefore, wild boars harbouring potentially pathogenicY. enterocolitica4/O:3 strains pose a challenge to public health.