The Gene ail for the Attachment-Invasion Locus Protein of Yersinia enterocolitica Biotype 1A Strains Is Located on the Genome of Novel Prophages

The attachment-invasion locus protein Ail of pathogenic Yersinia strains is an important virulence factor for both invasion of eucaryotic cells as well as serum resistance. In other Yersinia strains, e.g. those belonging to biotype (BT) 1A of Yersinia enterocolitica, ail has only occasionally been described. Sequence analysis of 370 BT 1A isolates in our laboratory revealed 41 (11.1%) being ail-positive. Most of these isolates were recovered from minced meat and wild boars and belong to 17 MLST allele profiles. A closer look at DNA sequences surrounding ail disclosed that the gene of most isolates is embedded in DNA regions encoding phage proteins. The genomes of four prophages belonging to four different phylogenetic clusters were determined and analysed by in silico studies. They have sizes of 34.9 and 50.7 kb and are closely related to each other, but not to known phages. Unlike other regions of the prophages, the integrases and attachment sites of some of them diverge leading to different integration sites in the isolates. In a fifth cluster, ail is relocated at a different position on the Y. enterocolitica chromosome, but surrounded by prophage-related sequences. In addition, highly pathogenic 1B/O:8 strains contain a DNA segment including ail that is similar to the prophage sequences determined in this study.