RESUMEN
A total of 30 isolates of enterotoxigenic E. coli. derived from diarrheal patients were examined for serotype and toxigenicity. The transferability of enterotoxin plasmid and plasmid profile analysis of enterotoxigenic E. coli. revealed that the strains with the same [O] serotype and toxigenicity carry closely related enterotoxin plasmids. Most strains of LT producers, [7/10] isolates transferred enterotoxin and trimethoprim resistance simultaneously indicating that they either carry a conjugative plasmids or a non conjugative enterotoxin plasmids coexisted with a conjugative cryptic plasmids. Our results predict that enterotoxigenic E. coli. [ETEC], particularly those producing only LT may no longer be restricted to a narrow range of [O] sero- types in the near future