The Gene Ail for the Attachment–Invasion Locus Protein of Yersinia enterocolitica Biotype 1A Strains Is Located on the Genomes of Novel Prophages

The attachment-invasion locus protein Ail of pathogenic <i>Yersinia</i> strains is an important virulence factor, both for invasion of eucaryotic cells and for serum resistance. In other <i>Yersinia</i> strains, e.g., those belonging to biotype (BT) 1A of <i>Yersinia enterocolitica</i>, <i>ail</i> has only occasionally been described. Sequence analysis of 370 BT 1A isolates in our laboratory revealed 41 (11.1%) which were <i>ail</i>-positive. Most of these isolates were recovered from minced meat and tonsils of wild boars, and belonged to 17 MLST allele profiles. A closer look at DNA sequences surrounding <i>ail</i> disclosed that the gene in most isolates is embedded in DNA regions encoding phage proteins. The genomes of four prophages belonging to four different phylogenetic clusters were determined and analyzed by in silico studies. These 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, <i>ail</i> is relocated at a position on the <i>Y. enterocolitica</i> chromosome that is several hundred kilobases apart from those of the other clusters, but surrounded by prophage-related sequences. In addition, highly pathogenic 1B/O:8 strains contain a DNA segment which includes <i>ail</i> and is 65 to 94% identical to the prophage sequences determined in this study.