Enterotoxigenic strains of Escherichia coli O128 are not restricted to subgroup ac but also belong to subgroups ab and abc.

Ninety strains of Escherichia coli O128 isolated in many different countries were examined. The majority (77 strains) belonged to the antigenic subgroup O128ab, and 41 of these strains produced heat-stable enterotoxin (ST), heat-labile enterotoxin (LT), or both. Eight strains were of the antigenic subgroup O128ac; six produced ST only, and two were nontoxigenic. Five strains were of the antigenic subgroup O128abc; two produced ST and LT, and three were nontoxigenic. Ten of the strains studied produced Vero cytotoxin, and all belonged to the antigenic subgroup O128ab. It was concluded that, contrary to the report of Guth et al. (B. E. C. Guth, M. L. M. Silva, I. C. A. Scaletsky, M. R. F. Toledo, and L. R. Trabulsi, Infect. Immun. 47:338-340, 1985), enterotoxigenic strains of E. coli O128 are not restricted to subgroup ac but also belong to the most common subgroup, ab.