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Serotypes and virulence genes of bovine Shigatoxigenic Escherichia coli (STEC) isolated from a feedlot in Argentina

2003; Elsevier BV; Volume: 100; Issue: 1-2 Linguagem: Inglês

10.1016/s0378-1135(03)00127-5

1873-2542

Nora Lía Padola, Marcelo E. Sanz, Jesús E. Blanco, Miguel Blanco, Jorge Blanco, Analía I. Etcheverría, Guillermo H Arroyo, M. A. Usera, A Parma,

Listeria monocytogenes in Food Safety

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 60 MDa 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.