The bactericidal effect and chemical reactions of acidified nitrite under conditions simulating the stomach

Aims: To examine the hypothesis of non-immune defence mechanisms based on n itrite. Methods and Results: The acidified media (nutrient broth or citrate-phospha te buffer) under aerobic conditions with additions of physiological levels of nitrite, L-ascorbic acid, iodide and thiocyanate were used to simulate g astric juice. The bactericidal effects of acidified nitrite on Escherichia coli and lactobacilli were investigated using bacterial plate counts. Conve rsion of acidified nitrite to nitric oxide, nitrogen dioxide and nitrate wa s also studied. Nitrite significantly increased the bactericidal effects on E. coli and lactobacilli. The bactericidal effects were enhanced by thiocy anate but not by L-ascorbic acid and iodide. L-Ascorbic acid and thiocyanat e, but not iodide, enhanced the decomposition of acidified nitrite in nutri ent broth. Acidified nitrite was converted to both nitric oxide and nitrate , but a portion of the acidified nitrite in nutrient broth may have been co nverted to other unidentified nitrogen compounds. Nitrogen dioxide was not detected in any of the samples. Conclusions: The bactericidal effects of nitrite appeared to be primarily r elated to nitrous acid, and possibly to other unidentified nitrogenous meta bolites, but not to nitric oxide and nitrogen dioxide. Significance and Impact of the Study: The potential role of nitrite as an a ntimicrobial substance in the stomach may be of some importance in the ecol ogy of the gastrointestinal tract and in host physiology.