Little heterogeneity among genes encoding heat-labile and heat-stable toxins of enterotoxigenic Escherichia coli strains isolated from diarrheal pigs.

To examine whether the heat-labile enterotoxin gene in porcine enterotoxigenic Escherichia coli (ETEC) strains is as divergent as in human ETEC strains, we sequenced the heat-labile and heat-stable toxin genes from 52 and 33 porcine ETEC strains, respectively. We found that the STa gene is identical, that the LT gene has only two mutations in 4 (of 52) strains, and that both mutations cause a reduction in GM1 binding and toxicity.