Production of heat-labile enterotoxin by strains of Aeromonas veronii bv veronii.

Three isolates of Aeromonas veronii bv veronii (2 environmental, one blood infection) were examined to see if they produce any enterotoxin and, if so, to determine its characteristics. Two isolates caused fluid accumulation in the initial rabbit ileal loop tests. The other strain did so after a single passage through the rabbit ileal loop. All the isolates showed gradual enhancement of fluid secretion after each subsequent passage. Inocula of 1 x 10(4) viable cells and 0.25 mL of culture filtrate caused fluid accumulation comparable to those of toxigenic Vibrio cholerae 569B. The enterotoxic activity was inactivated at higher temperature, and showed biological activity over a wide range of pH. The only histopathological change observed was depletion of mucous from goblet cells. The findings of the study indicate that strains of A. veronii bv veronii produce a heat-labile, pH-stable diarrhoeagenic factor without causing any damage to the intestinal mucosa.