Elevation of rat intestinal permeability by enterotoxigenic Escherichia coli in comparison to non-toxigenic E. coli and Salmonella typhimurium. Application of fluorescent dextran 3000 as permeability probe

Abstract The effect of bacterial enterotoxins on rat intestinal permeability properties was studied by comparing the effect of toxin-positive and toxin-negative Escherichia coli and Salmonella typhimurium inoculated into a segment of rat small intestine. Fluoresceinated dextran 3000 (FITC-D3; M _r 3000) was applied as permeability marker. The E. coli strain C922a-1 producing heat-labile (LT) and heat-stable (ST) enterotoxins and colonising factor CFA/II increased the transmural passage of the dextran probe into portal blood. In contrast, its plasmid-negative variant, a non-toxin producer lacking CFA, caused permeability changes indistinguishable from the bacteria-free nutrient broth control. Another pair of enterotoxigenic E. coli strains, 1628–14 (LT⁺, ST⁺, CFA/I⁺) and 1628–15 (LT⁺, ST^? and CFA/I^?) both increased the intestinal permeability. The observations indicate that the LT⁺-only E. coli strain 1628–15 has the ability to promote permeability of rat intestine. The toxin-negative, rough S. typhimurium 395MR10 bacteria had a very small effect on the permeability, which was also achieved with culture filtrate only.
It is concluded that enterotoxigenic E. coli (ETEC) can alter the properties of the mucosal barrier towards intermediate-sized molecules that could be of antigenic significance, or which could play a crucial role in the nutritional status of the host organism.