In vitro antimicrobial activity of bismuth subsalicylate and other bismuth salts.

This report demonstrates that bismuth subsalicylate (BSS) effectively inhibits growth of a number of bacterial strains known to cause diarrhea, including Escherichia coli, Salmonella, Shigella, and Campylobacter. Other bismuth salts and sodium salicylate, a hydrolysis product of BSS in the gut, also were examined and were shown to have various degrees of activity. Growth of the organisms was monitored in vitro by inoculating culture fluid that contained one of the compounds to be tested and determining the concentration of viable organisms over a 24-hour period. Control cultures of each organism were grown in the absence of bismuth subsalicylate. BSS inhibited growth of all organisms examined in a dose-dependent fashion. Reductions of 2-6 logs, as compared with controls, were observed in cultures grown in the presence of 10-50 mM BSS. Other bismuth salts displayed various degrees of inhibition. These results suggest that the efficacy of BSS as an antidiarrheal agent may be related to an antimicrobial mechanism of action.