Bacterial toxins: Enterotoxigenic Escherichia coli and diarrhea in man and animals
Enterotoxigenic Escherichia coli (ETEC) are distinguished from other virulence groups by production of colonization factors (fimbrial or afimbrial) and toxins. ETEC cause diarrhea in both man and animals through the action on the intestine of enterotoxins. Colonization of the intestinal mucosa allows efficient delivery of enterotoxins. ETEC enterotoxins are cytotonic, provoking fluid and electrolyte secretion without altering the cell tissue morphology. In humans, ETEC are responsible for travelers’ diarrhea. In animals, important diarrheal diseases and economic losses due to growth retardation, treatment and death are observed. Two types of toxins are produced: (1) heat-labile (LT) and (2) heat-stable (ST), comprising STa and STb. The action of these toxins together or independently provokes secretion. STb is a 48 amino acids peptide with a MW of 5200 Da comprising 2 disulfide bonds required for toxicity expression. This enterotoxin is mainly associated with porcine colibacillosis but E. coli isolates from humans with diarrhea have been shown to produce STb. This toxin is unrelated to STa both in sequence and mechanism of action. Little is known about internalisation of STb and the cascade of events leading to alteration of the intestine homeostasis.
J. Daniel Dubreuil
The Dubreuil laboratory is studying ETEC and in particular the low molecular weight heat-resistant STb enterotoxin. We are interested in knowing how STb is internalize in intestinal epithelial cells together with determining the pathway(s) involved in the intracellular signalling leading to watery diarrhea. To realize our aims we use animal models as well as cells in culture. Protein chemistry, mutagenesis, microscopy and flow cytometry analysis approaches, among others, are used. For recent laboratory publications please look in PubMed under Dubreuil JD. Open positions are available now for M.Sc. and Ph.D. If you consider graduate work, please contact Dr. Dubreuil directly.