International Microbiology, Vol 7, No 4 (2004)

Virulence genes and intimin types of Shiga-toxin-producing Escherichia coli isolated from cattle and beef products in Argentina

Miguel Blanco, Nora L. Padola, Alejandra Krüger, Marcelo E. Sanz, Jesús E. Blanco, Enrique A. González, Ghizlane Dahbi, Azucena Mora, María Isabel Bernárdez, Analía I. Etcheverría, Guillermo H. Arroyo, Paula M.A. Lucchesi, Alberto E. Parma, Jorge Blanco


A total of 153 Shiga-toxin-producing Escherichia coli (STEC) isolates from feces of cattle and beef products (hamburgers and ground beef) in Argentina were characterized in this study. PCR showed that 22 (14%) isolates carried stx1 genes, 113 (74%) possessed stx2 genes and 18 (12%) both stx1 and stx2. Intimin (eae), enterohemolysin (ehxA), and STEC autoagglutinating adhesin (saa) virulence genes were detected in 36 (24%), 70 (46%) and in 34 (22%) of the isolates, respectively. None of 34 saa-positive isolates carried the gene eae, and 31 were ehxA-positive. Fourteen (7 of serotype O26:H11 and 4 of serotype O5:H-) isolates had intimin β1, 16 isolates possessed intimin γ1 (11 of serotype O145:Hand 5 of serotype O157:H7), 5 isolates had intimin type ε1 (4 of serotypes O103:Hand O103:H2), and one isolate O111:H- showed intimin type θ/γ2. Although the 153 STEC isolates belonged to 63 different seropathotypes, only 12 accounted for 58% of isolates. Seropathotype ONT:H- stx2 (18 isolates) was the most common, followed by O171:H2 stx2 (12 isolates), etc. The majority (84%) of STEC isolates belonged to serotypes previously found in human STEC and 56% to serotypes associated with STEC isolated from patients with hemolytic uremic syndrome (HUS). Thus, this study confirms that cattle are a major reservoir of STEC pathogenic for humans. To our knowledge, this is the first study that described the presence of saa gene in STEC of serotypes O20:H19, O39:H49, O74:H28, O79:H19, O116:H21, O120:H19, O141:H7, O141:H8, O174:H21, and ONT:H21. The serotypes O120:H19 and O185:H7 were not previously reported in bovine STEC. [Int Microbiol 2004; 7(4):269-276]

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