title: Identification of four fimbria-encoding genomic islands that are highly specific for verocytotoxin-producing Escherichia coli serotype O157 strains.
abstract: Verocytotoxin-producing Escherichia coli causes zoonotic food- or waterborne infection that may be associated with massive outbreaks and with the serious complication of hemolytic uremic syndrome (HUS). Serotypes O157:H7 and O157:NM are more commonly associated with HUS and outbreaks than other serotypes, such as O26:H11. To determine whether a genetic basis exists for why serotype O157:H7/NM causes HUS and outbreaks more often than other serotypes, such as O26:H11, we conducted suppression subtractive hybridization (SSH) between the genomes of the sequenced O157:H7 strain EDL933 and CL1, a clinical serotype O26:H11 isolate. Genes from four EDL933 fimbria-encoding genomic O islands (OIs) (OI-1, -47, -141, and -154) were identified in the SSH library. OI-47 encodes several additional putative virulence factors, including secreted and signaling proteins, a hemolysin locus, a lipoprotein, an ABC transport system, and a lipid biosynthesis locus. The distribution of the OIs was investigated by PCR and Southern hybridization (when PCR was negative) with 69 VTEC strains belonging to 39 different serotypes corresponding to 5 seropathotypes that differ in their disease and epidemic potential. The four OIs described here were distributed almost exclusively in serotypes O157:H7 and O157:NM, which indicates that they may be associated with the ability of these strains to colonize human and/or animal intestinal tracts and to cause epidemic and serious disease more frequently than other serotypes. The occurrence of the four OIs in enteropathogenic E. coli O55:H7 strains is consistent with their vertical inheritance by VTEC O157:H7/NM from this clonally related ancestor.
authors.affiliation: Laboratory for Foodborne Zoonoses, Public Health Agency of Canada, 110 Stone Road West, Guelph, Ontario, Canada, N1G 3W4.
authors.forename: Songhai
authors.initials: S
authors.lastname: Shen
authors.forename: Mariola
authors.initials: M
authors.lastname: Mascarenhas
authors.forename: Robyn
authors.initials: R
authors.lastname: Morgan
authors.forename: Kris
authors.initials: K
authors.lastname: Rahn
authors.forename: Mohamed A
authors.initials: MA
authors.lastname: Karmali
mesh_terms: D019453:Escherichia coli O157 / Q000145:classification / Q000472:pathogenicity*; D010861:Fimbriae, Bacterial / Q000235:genetics*; D015723:Gene Library; D044404:Genomic Islands; D022603:Shiga Toxins / Q000096:biosynthesis*
chemical_list: D022603:Shiga Toxins