Aeromonas hydrophila toxins—intestinal fluid accumulation and mucosal injury in animal models

Strains of Aeromonas hydrophila were earlier shown to produce a heat-labile enterotoxin and two cytolytic toxins, alpha- and beta-haemolysin. These investigations have been extended. When separated from the cytolysins, the enterotoxin elicited fluid accumulation in rabbit intestinal loops. The electrolyte and albumin content of the fluid was similar to that of cholera toxin. The enterotoxin was non-injurious to the mucosa. Purified hemolysins did not give a positive loop test. They produced hemorrhagic enteritis with leakage of small amounts of hemorrhagic fluid. In electrolyte and albumin content this fluid differed from the fluid elicited by the enterotoxin. Prostaglandin inhibitors did not reduce the diarrheal response to Aeromonas enterotoxin. The cAMP inhibitor chlorpromazine reduced the fluid accumulation in rat and mice intestinal loops by 60%. Cholera toxin and Aeromonas enterotoxin may have a common pathway in the elicitation of intestinal fluid accumulation. By passage in intestinal loops, strains of A. hydrophila could regain lost enterotoxicity. Experimental diarrhea could not be induced in rabbits and rats with various enterotoxigenic strains of Aeromonas.