title: Prevalence of subtilase cytotoxin-encoding subAB variants among Shiga toxin-producing Escherichia coli strains isolated from wild ruminants and sheep differs from that of cattle and pigs and is predominated by the new allelic variant subAB2-2.
abstract: Subtilase cytotoxin (SubAB) is an AB5 toxin produced by Shiga toxin (Stx)-producing Escherichia coli (STEC) strains usually lacking the eae gene product intimin. Three allelic variants of SubAB encoding genes have been described: subAB1, located on a plasmid, subAB2-1, located on the pathogenicity island SE-PAI and subAB2-2 located in an outer membrane efflux protein (OEP) region. SubAB is becoming increasingly recognized as a toxin potentially involved in human pathogenesis. Ruminants and cattle have been identified as reservoirs of subAB-positive STEC. The presence of the three subAB allelic variants was investigated by PCR for 152 STEC strains originating from chamois, ibex, red deer, roe deer, cattle, sheep and pigs. Overall, subAB genes were detected in 45.5% of the strains. Prevalence was highest for STEC originating from ibex (100%), chamois (92%) and sheep (65%). None of the STEC of bovine or of porcine origin tested positive for subAB. None of the strains tested positive for subAB1. The allelic variant subAB2-2 was detected the most commonly, with 51.4% possessing subAb2-1 together with subAB2-2. STEC of ovine origin, serotypes O91:H- and O128:H2, the saa gene, which encodes for the autoagglutinating adhesin and stx2b were significantly associated with subAB-positive STEC. Our results suggest that subAB2-1 and subAB2-2 is widespread among STEC from wild ruminants and sheep and may be important as virulence markers in STEC pathogenic to humans.
authors.affiliation: Institute for Food Safety and Hygiene, Vetsuisse Faculty University of Zurich, Zurich, Switzerland.
authors.forename: Magdalena T
authors.initials: MT
authors.lastname: Nüesch-Inderbinen
authors.affiliation: Department of Food Microbiology, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstraße 28, D-70599 Stuttgart, Germany.
authors.forename: Joschua
authors.initials: J
authors.lastname: Funk
authors.affiliation: Institute for Food Safety and Hygiene, Vetsuisse Faculty University of Zurich, Zurich, Switzerland.
authors.forename: Nicole
authors.initials: N
authors.lastname: Cernela
authors.affiliation: Institute for Food Safety and Hygiene, Vetsuisse Faculty University of Zurich, Zurich, Switzerland.
authors.forename: Taurai
authors.initials: T
authors.lastname: Tasara
authors.affiliation: Institute of Food, Nutrition and Health, ETH Zürich, Schmelzbergstrasse 7, 8092 Zürich, Switzerland.
authors.forename: Jochen
authors.initials: J
authors.lastname: Klumpp
authors.affiliation: Department of Food Microbiology, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstraße 28, D-70599 Stuttgart, Germany.
authors.forename: Herbert
authors.initials: H
authors.lastname: Schmidt
authors.affiliation: Institute for Food Safety and Hygiene, Vetsuisse Faculty University of Zurich, Zurich, Switzerland. Electronic address: stephanr@fsafety.uzh.ch.
authors.forename: Roger
authors.initials: R
authors.lastname: Stephan
mesh_terms: D000483:Alleles; D000818:Animals; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004927:Escherichia coli Infections / Q000382:microbiology / Q000662:veterinary*; D029968:Escherichia coli Proteins / Q000235:genetics*; D014644:Genetic Variation; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012418:Ruminants; D017422:Sequence Analysis, DNA; D054323:Shiga-Toxigenic Escherichia coli / Q000235:genetics* / Q000302:isolation & purification; D013381:Subtilisins / Q000235:genetics*; D013552:Swine
chemical_list: D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D013381:Subtilisins; C527234:subtilase cytotoxin, E coli
keywords: Chamois; Ibex; Sheep; Shiga toxin-producing Escherichia coli (STEC); Subtilase cytotoxin (subAB)