A Genomic Island, Termed High-Pathogenicity Island, Is Present in Certain Non-O157 Shiga Toxin-Producing Escherichia coli Clonal Lineages

Abstract

Shiga toxin-producing Escherichia coli (STEC) strains cause a wide spectrum of diseases in humans. In this study, we tested 206 STEC strains isolated from patients for potential virulence genes including stx, eae, and enterohemorrhagicE. coli hly. In addition, all strains were examined for the presence of another genetic element, the high-pathogenicity island (HPI). The HPI was first described in pathogenic Yersiniaspecies and encodes the pesticin receptor FyuA and the siderophore yersiniabactin. The HPI was found in the genome of distinct clonal lineages of STEC, including all 31 eae-positive O26:H11/H− strains and 7 of 12 eae-negative O128:H2/H− strains. In total, the HPI was found in 56 (27.2%) of 206 STEC strains. However, it was absent from the genome of all 37 O157:H7/H−, 14 O111:H−, 13 O103:H2, and 13 O145:H− STEC isolates, all of which were positive for eae. Polypeptides encoded by the fyuA gene located on the HPI could be detected by using immunoblot analysis in most of the HPI-positive STEC strains, suggesting the presence of a functional yersiniabactin system. The HPI in STEC was located next to the tRNA gene asnT. In contrast to the HPI of other pathogenic enterobacteria, the HPI of O26 STEC strains shows a deletion at its left junction, leading to a truncated integrase geneint. We conclude from this study that theYersinia HPI is disseminated among certain clonal subgroups of STEC strains. The hypothesis that the HPI in STEC contributes to the fitness of the strains in certain ecological niches rather than to their pathogenic potential is discussed.

The Yersinia HPI is present in Serratia liquefaciens isolated from meat

“…High-pathogenicity island carrying strains have been found in various genera of Enterobacteriaceae mostly in strains of human origin (Karch et al 1999;Schubert et al 2000). In the present study Yersinia HPI is present in S. liquefaciens isolated from meat.…”

“…A larger deletion of a fragment spanning from ybtP to asn tRNA has been found in an isolate of K. oxytoca (Bach et al 2000) and a partial deletion of the int gene in an E. coli strain (Karch et al 1999). To investigate whether the HPI was inserted at the asn tRNA gene and whether the int gene was located adjacent to this locus in our strain, a PCR reaction was performed with a primer pair annealing to these two genes.…”

Yersinia HPI in septicemic Escherichia coli strains isolated from diverse hosts

“…1. The PCR fragment was sequenced and the deletion was found to be identical to a deletion in int previously identi¢ed in Shiga toxin E. coli serotype O26 strain 5720/96 [6].…”

“…Most known E. coli strains produce the catecholate siderophore enterobactin [9], and many clinical isolates also possess the hydroxamate siderophore aerobactin [13]. Recently, a third siderophore, yersiniabactin, coded by the Yersinia high pathogenicity island (HPI), was found in E. coli strains pathogenic to humans [6,12]. E¤cient iron uptake is most essential for bacteria which enter the bloodstream.…”

Yersiniabactin and other siderophores produced by clinical isolates ofEnterobacterspp. andCitrobacterspp.

“…The presence of the HPI was initially determined by PCR analysis with primers for yersiniabactin biosynthetic and receptor genes irp1, irp2 and fyuA [16]. Recombinant Taq polymerase and other PCR reagents were purchased from MBI Fermentas (Vilnius, Lithuania).…”