Enteropathogenic Escherichia coli strain RDEC-1 produces a novel electrogenic factor active on rabbit ileum in vitro

Background: Attaching and effacing Escherichia coli demonstrate marked spec ies specificity in inducing diarrhea, although its mechanism remains largel y unclear. The purpose of this study was to investigate the existence of a soluble, species-specific factor that induces diarrhea in an in vitro model . Methods: Stripped rabbit ileum was mounted in Ussing chambers,: and changes in potential difference and short-circuit current were monitored after the addition of bacterial culture supernatant. Results: The culture supernatant from rabbit-specific strain RDEC-1, but no t from human-specific enteropathogenic Escherichia coli strain E2348/69, in duced an increase in potential difference and short-circuit current in rabb it ileum mounted in Ussing chambers. This electrical signal was related to chloride ion secretion, was absent in colonic tissue, and was retained in t he 30 to 100-KDa fraction of the supernatant. Preliminary experiments faile d to show an involvement of calcium or cyclic nucleotides as intracellular messengers. RDEC-1 cured of a 42-MDa plasmid lost the enterotoxicity wherea s conjugation of the plasmid into the negative E. coli recipient HB101 resu lted in the expression of toxicity. Conclusions: The authors describe a novel, species-specific factor that hel ps to explain RDEC-1 diarrhea, which may be relevant to the pathogenesis of enteropathogenic Escherichia coli infection.