EXPRESSION OF HEAT-STABLE ENTEROTOXIN STB BY ADHERENT ESCHERICHIA-COLI IS NOT SUFFICIENT TO CAUSE SEVERE DIARRHEA IN NEONATAL PIGS

The role of Escherichia coli heat-stable enterotoxin B (STb) in neonat al porcine diarrhea caused by enterotoxigenic E. coli was examined by comparing adherent isogenic strains with or without STb. The cloned ST b gene (in the plasmid pRAS1) was electroporated into a nonenterotoxig enic strain (226M) which expresses the F41 adhesin. Strain 226M pRAS1 adhered and expressed STb in vivo, causing fluid secretion in ligated ileal loops in neonatal pigs. Although Strain 226M pRAS1 caused very m ild diarrhea in some orally inoculated neonatal pigs, the weight loss in these pigs was similar to that caused by the parental strain withou t STb. We conclude that STb does not significantly contribute to diarr hea caused by enterotoxigenic E. coli in neonatal pigs.