title: Studies on Escherichia coli serotype O157:H7 strains containing a 60-MDa plasmid and on 60-MDa plasmid-cured derivatives.
abstract: Seventeen strains of Escherichia coli serotype O157:H7 producing Shiga-like toxin were examined for the presence of plasmids and for the ability to adhere to HEp-2 and Intestine 407 cells. All of the strains possessed a common 60-MDa plasmid. To determine the role of the 60-MDa plasmid, plasmid-cured strains were compared with the parent strains for their ability to produce pili and to adhere to epithelial cells in culture. The total cell lysate protein and outer-membrane protein (OMP) profiles were also compared. Both the parent strains and their plasmid-cured derivatives produced pili. Immunofluorescence assay results indicated that the plasmid-cured and parent strains adhered equally well to HEp-2 and Intestine 407 cells; overall adherence was greater with intestinal cells than HEp-2 cells. SDS-PAGE of polypeptides synthesised in an E. coli system in vitro showed that plasmid DNA encodes c. 35 proteins. SDS-PAGE of OMP preparations demonstrated that the 60-MDa plasmid appears to be involved in the synthesis of a 33-kDa OMP. Two strains cured of the 60-MDa plasmid, one that possessed no plasmids and one that still contained a 2.2-MDa plasmid, produced exopolysaccharide (EPS) when cultured on solid medium at 25 degrees C. Two other strains, which were cured of the 60-MDa plasmid but contained a 4.5-MDa plasmid, did not produce visible amounts of EPS. Gas chromatography analysis showed that the EPS consisted of fucose, glucose and galactose in an approximate molar ratio of 2.0:0.9:1.1 and also had 7% of a uronic acid sugar as part of its structure.
authors.affiliation: Microbial Food Safety Research Unit, US Department of Agriculture, Philadelphia, PA 19118.
authors.forename: P M
authors.initials: PM
authors.lastname: Fratamico
authors.forename: S
authors.initials: S
authors.lastname: Bhaduri
authors.forename: R L
authors.initials: RL
authors.lastname: Buchanan
mesh_terms: D001422:Bacterial Adhesion; D001425:Bacterial Outer Membrane Proteins / Q000032:analysis; D001426:Bacterial Proteins / Q000032:analysis; D001427:Bacterial Toxins / Q000032:analysis; D002849:Chromatography, Gas; D003092:Colitis / Q000382:microbiology; D003603:Cytotoxins / Q000032:analysis; D004269:DNA, Bacterial / Q000032:analysis; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics / Q000472:pathogenicity* / Q000648:ultrastructure; D004927:Escherichia coli Infections / Q000382:microbiology; D010861:Fimbriae, Bacterial / Q000648:ultrastructure; D005455:Fluorescent Antibody Technique; D005516:Food Microbiology; D006471:Gastrointestinal Hemorrhage / Q000382:microbiology; D006801:Humans; D008855:Microscopy, Electron, Scanning; D010957:Plasmids; D011135:Polysaccharides, Bacterial / Q000032:analysis; D022622:Shiga Toxin 1; D014774:Virulence
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D003603:Cytotoxins; D004269:DNA, Bacterial; D011135:Polysaccharides, Bacterial; D022622:Shiga Toxin 1