title: Serotypes and virulence genes of bovine Shigatoxigenic Escherichia coli (STEC) isolated from a feedlot in Argentina.
abstract: Grazing-fed cattle were previously demonstrated to be reservoir of non-O157 Shigatoxigenic Escherichia coli (STEC) serotypes in Argentina. The acid-resistance of some STEC strains makes it reasonable to assume the presence in feedlot of particular STEC serotypes. Fifty-nine animals were sampled every 2 weeks during 6 months by rectal swabs. Twenty-seven of 59 animals (45.8%) were shown to be Stx2(+); 3/59 (5.1%) carried Stx1(+) and 7/59 (11.9%) were Stx1(+) Stx2(+). Among 44 STEC isolates, 31 isolates were associated to 10 O serogroups (O2, O15, O25, O103, O145, O146, O157, O171, O174, O175) and 13 were considered non-typable (NT). Six H antigens (H2, H7, H8, H19, H21, H25) were distributed in 21 isolates whereas 23 were non-mobile (H-). Seventeen of 44 strains (38.6%) were eaeA(+) and 14 (31.8%) harbored the 60MDa plasmid. The megaplasmid (Mp) and eaeA gene were simultaneously found in a limited number of serotypes belonging to the enterohaemorrhagic E. coli (EHEC). E. coli O157:H7 strains, isolated from four (6.8%) animals, corresponded to the Stx2(+), eaeA(+), Mp(+) pattern. Three O157:H7 strains belonged to phage type 4 and the other strain was atypical. Many serotypes isolated from grain-fed cattle (O2:H25, O15:H21, O25:H19, O145:H-, O146:H-, O146:H21, O157:H7, O175:H8) also differed from those isolated by us previously from grazing animals. The serotypes O15:H21, O25:H19 and O175:H8 had not been identified at present as belonging to STEC. This work provides new data for the understanding of the ecology of STEC in grain-fed cattle and confirms that cattle are an important reservoir of STEC.
authors.affiliation: Laboratorio de Inmunoquímica y Biotecnología, FCV, UNICEN, Pinto 399 (7000) Tandil, Argentina.
authors.forename: Nora L
authors.initials: NL
authors.lastname: Padola
authors.forename: Marcelo E
authors.initials: ME
authors.lastname: Sanz
authors.forename: Jesús E
authors.initials: JE
authors.lastname: Blanco
authors.forename: Miguel
authors.initials: M
authors.lastname: Blanco
authors.forename: Jorge
authors.initials: J
authors.lastname: Blanco
authors.forename: Analía I
authors.initials: AI
authors.lastname: Etcheverria
authors.forename: Guillermo H
authors.initials: GH
authors.lastname: Arroyo
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Usera
authors.forename: Alberto E
authors.initials: AE
authors.lastname: Parma
mesh_terms: D018829:Adhesins, Bacterial / Q000737:chemistry / Q000235:genetics; D000372:Agglutination Tests / Q000662:veterinary; D000818:Animals; D001118:Argentina; D001434:Bacteriophage Typing / Q000662:veterinary; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004926:Escherichia coli / Q000145:classification* / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity; D004927:Escherichia coli Infections / Q000382:microbiology / Q000662:veterinary*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics; D019081:O Antigens / Q000235:genetics; D016133:Polymerase Chain Reaction / Q000662:veterinary; D012703:Serotyping / Q000662:veterinary; D022622:Shiga Toxin 1 / Q000737:chemistry / Q000235:genetics*; D022641:Shiga Toxin 2 / Q000737:chemistry / Q000235:genetics*; D014774:Virulence
chemical_list: D018829:Adhesins, Bacterial; D002352:Carrier Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D019081:O Antigens; D022622:Shiga Toxin 1; D022641:Shiga Toxin 2; C073819:eaeA protein, E coli