Double-blind comparison of bismuth subsalicylate and placebo in the prevention and treatment of enterotoxigenic Escherichia coli-induced diarrhea in volunteers.

Enterotoxigenic Escherichia coli cause most traveler's diarrhea in Third World countries. We tested bismuth subsalicylate as prophylactic therapy and as treatment for enterotoxigenic E. coli-induced diarrhea. Thirty-two healthy hospitalized volunteers were challenged orally with enterotoxigenic E. coli, strain H10407 (serotype 078:K80:H11). Administration of 600-mg doses of bismuth subsalicylate or placebo was begun 8 h before bacterial challenge. Doses were taken at 8 h and 2 h before, and at 2 h and 4 h after, the E. coli challenge and were continued four times a day for 3 additional days. The maximum prophylactic bismuth subsalicylate dose was 9.6 g. Those experiencing diarrhea were rerandomized to receive bismuth subsalicylate or placebo, given as 300 mg every 30 min for a total of 2.4 g of bismuth subsalicylate, in eight doses. Diarrhea occurred in 9 of the 16 (56%) subjects receiving placebo and in 2 of the 15 (13%) subjects receiving bismuth subsalicylate, p less than 0.03. This study confirms the effectiveness of bismuth subsalicylate in preventing traveler's (enterotoxigenic E. coli) diarrhea, and shows that bismuth subsalicylate in other than liquid form is effective. Enterotoxigenic E. coli were recovered less frequently from those receiving bismuth subsalicylate than from those receiving placebo, suggesting that bismuth subsalicylate prevents diarrhea by reducing the number or multiplication of enterotoxigenic E. coli. In vitro studies revealed that bismuth subsalicylate and its components each were bactericidal at concentrations possibly attained during the clinical trial.