Serotypes, Virulence Genes, and Intimin Types of Shiga Toxin (Verotoxin)-Producing Escherichia coli Isolates from Cattle in Spain and Identification of a New Intimin Variant Gene (eae- )

A total of 514 Shiga toxin-producing Escherichia coli (STEC) isolates from diarrheic and healthy cattle in Spain were characterized in this study. PCR showed that 101 (20%) isolates carried stx1 genes, 278 (54%) possessed stx2 genes, and 135 (26%) possessed both stx1 and stx2. Enterohemolysin (ehxA) and intimin (eae) virulence genes were detected in 326 (63%) and in 151 (29%) of the isolates, respectively. STEC isolates belonged to 66 O serogroups and 113 O:H serotypes (including 23 new serotypes). However, 67% were of one of these 15 serogroups (O2, O4, O8, O20, O22, O26, O77, O91, O105, O113, O116, O157, O171, O174, and OX177) and 52% of the isolates belonged to only 10 serotypes (O4:H4, O20:H19, O22:H8, O26:H11, O77:H41, O105:H18, O113:H21, O157:H7, O171:H2, and ONT:H19). Although the 514 STEC isolates belonged to 164 different seropathotypes (associations between serotypes and virulence genes), only 12 accounted for 43% of isolates. Seropathotype O157:H7 stx2 eae1 ehxA (46 isolates) was the most common, followed by O157:H7 stx1 stx2 eae1 ehxA (34 isolates), O113:H21 stx2 (25 isolates), O22:H8 stx1 stx2 ehxA (15 isolates), O26:H11 stx1 eae1 ehxA (14 isolates), and O77:H41 stx2 ehxA (14 isolates). Forty-one (22 of serotype O26:H11) isolates had intimin 1, 82 O157:H7 isolates possessed intimin 1, three O111:Hisolates had intimin type 2, one O49:Hstrain showed intimin type , 13 (six of serotype O103:H2) isolates had intimin type and eight (four of serotype O156:H-) isolates had intimin . We have identified a new variant of the eae intimin gene designated (xi) in two isolates of serotype O80:H-. The majority (85%) of bovine STEC isolates belonged to serotypes previously found for human STEC organisms and 54% to serotypes associated with STEC organisms isolated from patients with hemolytic uremic syndrome. Thus, this study confirms that cattle are a major reservoir of STEC strains pathogenic for humans.