Escherichia coliSTb toxin and colibacillosis: knowing is half the battle

Abstract

Expression of both adherence and enterotoxin expression are required for enterotoxigenic Escherichia coli (ETEC) strains to cause colibacillosis. ETEC strains are responsible for diarrhea in humans and animals by production of various enterotoxins. For many years, the role of the heat-stable E. coli enterotoxin STb as a diarrhea-causing toxin in animals, and in particular in swine, has been controversial. In fact, although the presence of STb-positive E. coli strains and diarrhea in animals is frequently observed, the difficulty of reproducing the pathology in an animal model was interpreted as a lack of toxicity. Recently, new light was shed on the activity of STb in intestinal ligated loops and in pigs orally inoculated with STb-positive E. coli strains. This minireview revisits the effects of STb on the intestinal epithelium and enlightens the significance of STb in swine colibacillosis. The interaction of STb toxin with other E. coli enterotoxins and dual ETEC/enteropathogenic E. coli or ETEC/attaching effacing E. coli infections are also discussed.

Escherichia coli virulence factors

“…STaP and STaH are 18 and 19 amino-acid peptides respectively of a molecular weight of less than 2 kDa (Moseley et al, 1983), whereas STb is a 48 amino-acid peptide of ca. 5 kDa (Dubreuil, 2008) and EAST1 is a 38 amino-acid toxin of ca. 4 kDa (Savarino et al, 1993).…”

“…STaH, STaP, and probably EAST1 (based on structural similarity), exert their toxicity via activation of an intra-cellular cascade (Sears and Kaper, 1996;Kaper et al, 2004;Gyles and Fairbrother, 2010), while STb seems to act as a non-specific pore-forming toxin (Gonç alves et al, 2007;Dubreuil, 2008). If newborn calves, lambs, piglets and babies in developing countries are sensitive to the action of STaP and/or STaH that can also be involved in traveller's diarrhoea, the in vivo roles of STb and EAST1 are still controversial (Nataro and Kaper, 1998;Nagy and Fekete, 1999;Kaper et al, 2004;Dubreuil, 2008;Gyles and Fairbrother, 2010;Konno et al, 2011).…”

Escherichia coli STb toxin induces apoptosis in intestinal epithelial cell lines

“…The susceptibility of swine to ETEC will vary according to age: piglets younger than one week experience higher mortality rates than piglets older than one week. Moreover, ETEC triggers weight loss and growth retards in piglets older than one week indicating the age of the animal influences on the outcome of the disease developed (Dubreuil, 2008). As the swine commonly infected with ETEC are destined to the porcine industry, morbidity and mortality in these animals caused by ETEC constitute an important source of financial losses in the porcine industry .…”

“…Heat-stable enterotoxin b (STb) is one of the toxins produced by ETEC and is most commonly associated with porcine diarrhea (Dubreuil, 2008). Aside from causing diarrhea, STb induces morphological changes at the histological and cellular levels.…”

The Whole Shebang: The Gastrointestinal Tract,Escherichia coliEnterotoxins and Secretion

“…ETEC, for example, possesses two major virulence factors. Specific adherence appendices called fimbriae mediating adherence to the host epithelium (Dubreuil, 2008). Afimbrial adherence factor can also be produced as, for example, the adhesin involved in diffuse adherence (AIDA).…”