Prevention of Diarrhea Caused by Enterotoxigenic Escherichia coli: Lessons Learned with Volunteers

Abstract

The effectiveness of bismuth subsalicylate in the prevention and treatment of diarrhea induced in volunteers by a single strain of enterotoxigenic Escherichia coli and a standard inoculum size was evaluated. Bismuth subsalicylate (500 mg in a solid dosage form) was administered 8 hours and 2 hours before and 2 hours and 4 hours after the E. coli challenge; treatment was continued four times a day for three additional days. Volunteers experiencing diarrhea were re-randomized to receive placebo or bismuth subsalicylate (300 mg every 30 minutes, for a total of 2.4 g of bismuth subsalicylate, in eight doses). Diarrhea occurred in nine (56%) of the 16 volunteers receiving placebo and in two (13%) of the 15 volunteers receiving bismuth subsalicylate (P less than .03). In vitro studies revealed that bismuth subsalicylate and its components each were bactericidal at concentrations possibly attained during the clinical trial. The effect of the dosage form (solid vs. liquid), the relation of drug administration to meals, and how these variables might greatly influence the effectiveness of bismuth subsalicylate prophylaxis for travelers' diarrhea were considered.