Infection and Immunity, November 2001, p. 6863-6873, Vol. 69, No. 11
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.69.11.6863-6873.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Institut für Hygiene und Mikrobiologie der Universität Würzburg1 and Institut für Molekulare Infektionsbiologie der Universität Würzburg,3 Würzburg, Germany, and Division of Gastroenterology, Children's Hospital and Regional Medical Center and the Departments of Pediatrics and Microbiology, University of Washington School of Medicine, Seattle, Washington2
Received 16 May 2001/Returned for modification 19 July 2001/Accepted 15 August 2001
The selC tRNA gene is a common site for the
insertion of pathogenicity islands in a variety of bacterial enteric
pathogens. We demonstrate here that Escherichia coli
that produces Shiga toxin 2d and does not harbor the locus of
enterocyte effacement (LEE) contains, instead, a novel genomic island.
In one representative strain (E. coli
O91:H
strain 4797/97), this island is 33,014 bp long and,
like LEE in E. coli O157:H7, is
integrated 15 bp downstream of selC. This E. coli O91:H
island
contains genes encoding a novel serine protease, termed EspI; an
adherence-associated locus, similar to iha of
E. coli O157:H7; an E.
coli vitamin B12 receptor (BtuB); an
AraC-type regulatory module; and four homologues of E.
coli phosphotransferase proteins. The remaining sequence
consists largely of complete and incomplete insertion sequences,
prophage sequences, and an intact phage integrase gene that is located
directly downstream of the chromosomal selC. Recombinant
EspI demonstrates serine protease activity using pepsin A and human
apolipoprotein A-I as substrates. We also detected Iha-reactive protein
in outer membranes of a recombinant clone and 10 LEE-negative, Shiga
toxin-producing E. coli (STEC) strains by
immunoblot analysis. Using PCR analysis of various STEC,
enteropathogenic E. coli, enterotoxigenic
E. coli, enteroaggregative
E. coli, uropathogenic E.
coli, and enteroinvasive E.
coli strains, we detected the iha
homologue in 59 (62%) of 95 strains tested. In contrast,
espI and btuB were present in only two
(2%) and none of these strains, respectively. We conclude that the
newly described island occurs exclusively in a subgroup of STEC strains
that are eae negative and contain the variant stx2d gene.
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