Escherichia coli STb Enterotoxin: A Multifaceted Molecule

Abstract

Enterotoxigenic Escherichia coli (ETEC) produce heat-labile and heat-stable toxins. These toxins are active on the epithelial cells of the small intestine of man and animals, affecting the fluid homeostasis. One of the heat-stable toxins enterotoxin b (STb) is responsible for secretory diarrhea in animals and more specifically in pigs. Recent studies have provided information on the nature of its receptor and the structure-function of the toxin. The toxin was shown to form oligomers and this process seems indispensable for toxicity expression. As observed with in vitro models and cells in culture, diverse activities were determined for STb and some or all of these may account for the secretion resulting from the activity of this toxin. The next step will be to determine quantitatively how important each of these activities is on fluid secretion. The relative importance of STb compared to other ETEC toxins has been clarified in recent years. As STb is now recognized as a major player in post-weaning diarrhea in pigs, the focus has been on ways to prevent its toxicity. For example, vaccines composed of multivalent toxin molecules were designed, and preliminary results indicate that it could represent a reliable way to protect from ETEC intoxication. As described for many other bacterial toxins, in the near future, STb could be utilized as a tool to decipher cellular physiological process.