Abstract
BackgroundPigs are regarded as the main reservoir for human pathogenic Yersinia enterocolitica, which is dominated by bioserotype 4/O:3. Other animals, including sheep, have occasionally been reported as carriers of pathogenic strains of Y. enterocolitica. To our knowledge, this is the first study performed in the Nordic countries in which the presence of Y. enterocolitica in sheep is investigated.MethodsTonsils and faecal samples collected from sheep slaughtered on the island Gotland (Sweden) from September 2010 through January 2011 were analysed for presence of Y. enterocolitica. In an attempt to maximize recovery, several cultural strategies were applied. Various non-selective media were used and different temperatures and durations of the enrichment were applied before subculturing on Cefsulodin Irgasan Novobiocin (CIN) agar. Presumptive Y. enterocolitica colonies were subjected to urease, API 20E and agglutination test. Yersinia enterocolitica isolates were biotyped, serotyped, and tested for pathogenicity using a TaqMan PCR directed towards the ail-gene that is associated with human pathogenic strains of Y. enterocolitica.ResultsThe samples collected from 99 sheep yielded 567 presumptive Y. enterocolitica colonies. Eighty urease positive isolates, from 35 sheep, were identified as Y. enterocolitica by API 20E. Thirty-four of 35 further subtyped Y. enterocolitica isolates, all from faecal samples, belonged to biotype 1A serotype O:5, O:6. O:13,7 and O:10. One strain was Yersinia mollaretii serotype O:62. No human pathogenic strains of Y. enterocolitica were found in the investigated sheep. Other species identified were Y. kristensenii (n = 4), Y. frederiksenii/intermedia (n = 3), Providencia rettgeri (n = 2), Serratia marcescens (n = 1) and Raoultella ornithinolytica (n = 1).ConclusionsThis study does not support the hypothesis that sheep play an important role in transmission of the known human pathogenic Y. enterocolitica in the studied geographical region. However, because there are studies indicating that some strains of Y. enterocolitica biotype 1A may cause disease in humans, the relative importance of sheep as carriers of human pathogenic strains of Y. enterocolitica remains unclear. Tonsils do not appear to be favourable sites for Y. enterocolitica biotype 1A in sheep.
Highlights
Pigs are regarded as the main reservoir for human pathogenic Yersinia enterocolitica, which is dominated by bioserotype 4/O:3
Culture and identification of Y. enterocolitica tonsil and faecal samples were collected from 105 sheep after slaughter, only samples from 99 sheep were used
API 20E identified the majority (80/95) of the urease isolates as belonging to the species Y. enterocolitica, in varying degree according to the API species definition: four with ‘Very good identification’, 66 with ‘Good identification’; five with ‘Very good identification to the genus’ and five with ‘Doubtful profile’ Y. enterocolitica was mentioned as one significant taxa
Summary
Pigs are regarded as the main reservoir for human pathogenic Yersinia enterocolitica, which is dominated by bioserotype 4/O:3. Other animals, including sheep, have occasionally been reported as carriers of pathogenic strains of Y. enterocolitica. To our knowledge, this is the first study performed in the Nordic countries in which the presence of Y. enterocolitica in sheep is investigated. Human pathogenic strains of Yersinia enterocolitica cause yersiniosis, a food-borne zoonosis. It is a gastrointestinal pathogen causing symptoms which vary depending on the age of the host and the bioserotype of the infecting strain. Most of the reported yersiniosis cases in Europe are caused by Y. enterocolitica biotype 4, serotype O:3 [4]. There are, studies indicating that some of the 1A strains have the ability to cause disease in humans, they lack the classical virulence markers [7,8]
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