1 Two copies of the ail gene found in Yersinia enterocolitica and Yersinia 2 kristensenii 3 4 Suvi Joutsena,b, Per Johanssona, Riikka Laukkanen-Niniosa,c, Johanna Björkrotha and Maria 5 Fredriksson-Ahomaaa 6 7 aDepartment of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, 8 P.O.Box 66 (Agnes Sjöbergin katu 2), 00014 University of Helsinki, Finland 9 bRisk Assessment Unit, Finnish Food Authority, Helsinki, Finland 10 cFood Safety Unit, Finnish Food Authority, Helsinki, Finland 11 12 Corresponding author: 13 E-mail address:
[email protected] 1 14 Abstract 15 16 Yersinia enterocolitica is the most common Yersinia species causing foodborne infections in 17 humans. Pathogenic strains carry the chromosomal ail gene, which is essential for bacterial 18 attachment to and invasion into host cells and for serum resistance. This gene is commonly 19 amplified in several PCR assays detecting pathogenic Y. enterocolitica in food samples and 20 discriminating pathogenic isolates from non-pathogenic ones. We have isolated several non- 21 pathogenic ail-positive Yersinia strains from various sources in Finland. For this study, we 22 selected 16 ail-positive Yersinia strains, which were phenotypically and genotypically 23 characterised. Eleven strains were confirmed to belong to Y. enterocolitica and five strains to 24 Yersinia kristensenii using whole-genome alignment, Parsnp and the SNP phylogenetic tree. 25 All Y. enterocolitica strains belonged to non-pathogenic biotype 1A. We found two copies of 26 the ail gene (ail1 and ail2) in all five Y. kristensenii strains and in one Y. enterocolitica 27 biotype 1A strain. All 16 Yersinia strains carried the ail1 gene consisting of three different 28 sequence patterns (A6-A8), which were highly similar with the ail gene found in high- 29 pathogenic Y.