Histochemical tracing of bismuth in Helicobacter pylori after in vitro exposure to bismuth citrate

Background: Bismuth-containing drugs are widely used in the treatment of He licobacter pylori associated peptic ulcer. The mechanism of action of bismu th salts is, however not fully understood, and at present no histochemical techniques for the demonstration of bismuth salts is, are available. The ai ms were to present a histochemical method for the detection of bismuth in H . pylori and to demonstrate bismuth uptake in H. pylori after in vitro expo sure to bismuth citrate. Methods: H. pylori cultures (the strain used in th is study was CCUG 17874), were exposed to bismuth citrate at different conc entrations (0, 4.6, 80. 200 muM) and for different lengths of time (0 min, 15 min. 1 h, 24 h, 48 h). The samples were fixed in glutaraldehyde, centrif uged, and exposed to autometallographic (AMG) development in order to detec t bismuth histochemically. Results: A detailed protocol on the AMG bismuth technique on H. pylori exposed to bismuth in vitro is given. This method re sults in easily detectable AMG grains of silver enhanced bismuth particles at the electron microscopical level, and shows that bismuth accumulates. in ii. pylori, predominantly near the wall of the bacteria. Bismuth uptake is followed by bacterial degeneration. Conclusion: The present technique with its ability to trace bismuth constitutes a valuable tool in the efforts of clarifying the mechanism of action of bismuth on H. pylori, and supports t he notion that bismuth has an antimicrobial activity in itself.