title: Identification of the anti-terminator qO111:H)- gene in Norwegian sorbitol-fermenting Escherichia coli O157:NM.
abstract: Sorbitol-fermenting Escherichia coli O157:NM (SF O157) is an emerging pathogen suggested to be more virulent than nonsorbitol-fermenting Escherichia coli O157:H7 (NSF O157). Important virulence factors are the Shiga toxins (stx), encoded by stx1 and/or stx2 located within prophages integrated in the bacterial genome. The stx genes are expressed from p(R)             (')  as a late protein, and anti-terminator activity from the Q protein is necessary for read through of the late terminator t(R)             (')  and activation of p(R)             (') . We investigated the regulation of stx2(EDL933)  expression at the genomic level in 17 Norwegian SF O157. Sequencing of three selected SF O157 strains revealed that the anti-terminator q gene and genes upstream of stx2(EDL933)  were identical or similar to the ones observed in the E. coli O111:H- strain AP010960, but different from the ones observed in the NSF O157 strain EDL933 (AE005174). This suggested divergent stx2(EDL933) -encoding bacteriophages between NSF O157 and the SF O157 strains (FR874039-41). Furthermore, different DNA structures were detected in the SF O157 strains, suggesting diversity among bacteriophages also within the SF O157 group. Further investigations are needed to elucidate whether the q(O111:H)             (-)  gene observed in all our SF O157 contributes to the increased virulence seen in SF O157 compared to NSF O157. An assay for detecting q(O111:H)             (-)  was developed.
authors.affiliation: Department of Foodborne Infections, The Norwegian Institute of Public Health, Oslo, Norway.
authors.forename: Kjersti
authors.initials: K
authors.lastname: Haugum
authors.forename: Bjørn-Arne
authors.initials: BA
authors.lastname: Lindstedt
authors.forename: Inger
authors.initials: I
authors.lastname: Løbersli
authors.forename: Georg
authors.initials: G
authors.lastname: Kapperud
authors.forename: Lin Thorstensen
authors.initials: LT
authors.lastname: Brandal
mesh_terms: D001483:Base Sequence; D004927:Escherichia coli Infections / Q000382:microbiology; D019453:Escherichia coli O157 / Q000145:classification / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D005285:Fermentation; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics*; D039002:Prophages / Q000235:genetics; D022641:Shiga Toxin 2 / Q000235:genetics* / Q000378:metabolism; D013012:Sorbitol / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; D022641:Shiga Toxin 2; D013012:Sorbitol