Mechanism of action of bismuth subsalicylate
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Antimicrobial Mechanism of Bismuth Subsalicylate
Bismuth subsalicylate (BSS) acts as an antimicrobial agent by directly inhibiting the growth of a wide range of diarrhea-causing bacteria, including Escherichia coli, Salmonella, Shigella, Campylobacter, and Clostridium difficile. It achieves this by binding to bacterial membranes and entering the bacterial cells, leading to a rapid decrease in intracellular ATP and ultimately bacterial death. This effect is dose-dependent and can result in a significant reduction in viable bacterial populations within hours of exposure. BSS also demonstrates activity against viral pathogens such as norovirus, reducing their infectivity in vitro. The antimicrobial action is further enhanced in acidic environments, such as the stomach, where BSS is converted to other bismuth salts and releases salicylate, both of which contribute to its bactericidal effects 3489.
Inhibition of Bacterial Toxins and Motility
BSS inhibits the activity of enterotoxins produced by bacteria like Vibrio cholerae and E. coli. It can inactivate these toxins before they bind to the intestinal mucosa, significantly reducing toxin-mediated fluid accumulation and diarrhea. Additionally, the salicylate component of BSS can suppress the synthesis of flagellin and flagella in gram-negative bacteria, which are essential for bacterial motility and colonization, particularly in Helicobacter pylori. This dual action—direct toxin inactivation and interference with bacterial motility—contributes to BSS’s effectiveness in treating gastrointestinal infections 25.
Protective Effects on Gastrointestinal Mucosa
BSS provides a protective coating on the gastrointestinal mucosa, shielding it from noxious stimuli and reducing the formation of ulcers and erosions. This coating effect has been observed in animal models, where BSS particles were found adhering to the stomach lining, significantly reducing ulceration caused by stress, alcohol, or irritants. In the esophagus, BSS protects against pepsin-induced injury by inhibiting the proteolytic activity of pepsin, thereby preserving mucosal integrity and reducing inflammation 67.
Reduction of Hydrogen Sulfide in the Colon
BSS binds to hydrogen sulfide (H₂S) in the colon, leading to a dramatic reduction in its release. Since H₂S is a toxic gas implicated in the pathogenesis of conditions like ulcerative colitis and is a major contributor to flatus odor, BSS’s ability to lower H₂S levels may have additional therapeutic benefits for gastrointestinal health and symptom control .
Conclusion
Bismuth subsalicylate acts through multiple mechanisms: it directly kills bacteria and viruses, inactivates bacterial toxins, suppresses bacterial motility, protects the gastrointestinal mucosa, and reduces harmful gas production in the colon. These combined actions explain its effectiveness in treating and preventing a variety of gastrointestinal disorders, particularly those involving infection and inflammation 23456789+1 MORE.
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