A genomic island, termed high-pathogenicity island, is present in certain non-O157 Shiga toxin-producing Escherichia coli clonal lineages - PubMed (original) (raw)

A genomic island, termed high-pathogenicity island, is present in certain non-O157 Shiga toxin-producing Escherichia coli clonal lineages

H Karch et al. Infect Immun. 1999 Nov.

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 enterohemorrhagic E. 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 Yersinia species 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 gene int. We conclude from this study that the Yersinia 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.

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Figures

FIG. 1

FIG. 1

Physical map of the HPI element of pathogenic yersiniae. Important genes are indicated by large black arrows and include the following: asnT and int boundary genes; ybtS, ybtQ, ybtA, irp2, irp1, ybtU, ybtT, and ybtE, constituting the siderophore yersiniabactin biosynthetic gene cluster; fyuA, encoding the receptor for yersiniabactin and pesticin; and IS_100_ insertion element (7, 13, 34, 38). PCR primers used to target single HPI genes (panel A, regions III to VIII, X, and XI) or to link consecutive genes (panel A, regions I, II, and IX, and panel B) are indicated by small arrows, and nucleotide sequences of the primers are given in Table 2.

FIG. 2

FIG. 2

Alignment of the deduced amino acid sequences of the integrases of Y. pestis (first line), Y. pseudotuberculosis (second line), STEC strain 3172/97 (third line), and STEC strain 5720/96 (fourth line). Translation of the latter sequence was performed without consideration of the frameshift resulting from the deletion of 347 bp. Bold letters represent differences in the amino acid sequence from the sequence of Y. pestis in the first line. Dashes in the last line indicate amino acid residues that are not present in this sequence (deletions). The deduced amino acid sequences of the Y. pestis and Y. pseudotuberculosis integrases are based on references and .

FIG. 3

FIG. 3

Immunoblot of outer membrane proteins probed with anti-FyuA rabbit serum. The arrow indicates the FyuA protein band. Lane 1, Y. pseudotuberculosis O1 (HPI+); lane 2, E. coli K-12 MG1655 (HPI−); lane 3, EAEC strain 17-2 (HPI+); lane 4, STEC strain O157:H7 3268/90 (HPI−); lane 5, STEC strain O62:H− 4595/97 (HPI−); lane 6, STEC strain O40:H− 4828/97 (HPI−); lane 7, STEC strain O103:H− 4797/97 (HPI−); lane 8, STEC strain O128:H2 3115/97 (HPI+); lane 9, STEC strain O128:H2 3172/97 (HPI+); lane 10, STEC strain ONT:H− 4941/97 (HPI+); lane 11, STEC strain O3:H10 5726/96 (HPI+); lane 12, STEC strain O60:H− 3357/98 (HPI+); lane 13, STEC strain Orough:H− 0512E015 (HPI+); lane 14, STEC strain O26:H11 6061/96 (HPI+). Molecular mass is shown on the right.

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