Comparison of phenotypes of stx-negative and stx-positive E. coli strains of serotypes O26:H11/NM, O103:H2/NM, O121:H19, O145:H28/NM, and O157:H7/NM.

aThe phenotypes were determined as described in Materials and Methods.bNM, nonmotile; stx−, stx-negative; stx+, stx-positive. n, number of strains tested; +, all strains tested (n) expressed the phenotype; −, none of the strains tested (n) expressed the phenotype; if a subset of the strains expressed the phenotype, the percentage is given in parenthesis.cThe CDT-V titers were 1∶4–1∶16 in both stx-negative and stx-positive strains as determined by Chinese hamster ovary cell assay [26].