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

PADOLA, NORA L.; SANZ, MARCELO, E; BLANCO, JESÚS E.; BLANCO, MIGUEL; BLANCO, JORGE; ETCHEVERRÍA, ANALÍA I.; ARROYO, GUILLERMO H.; USERA, MIGUEL A.; PARMA, ALBERTO E.

VETERINARY MICROBIOLOGY

Elsiever Science B.V.

Lugar: Amsterdam- Holanda; Año: 2004 vol. 100 p. 3 - 9

0378-1135

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.