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. 1998 Mar;42(3):334–337. doi: 10.1136/gut.42.3.334

Helicobacter pylori is killed by nitrite under acidic conditions

R Dykhuizen 1, A Fraser 1, H McKenzie 1, M Golden 1, C Leifert 1, N Benjamin 1
PMCID: PMC1727019  PMID: 9577337

Abstract

Background—Due to the expression of urease, Helicobacter pylori is able to establish itself in the human stomach under acidic conditions. A novel host defence mechanism was recently proposed, suggesting that the formation of salivary nitrite in symbiosis with facultative anaerobic bacteria in the oropharynx, is aimed at enhancing the antimicrobial activity of gastric juice. 
Aims—To investigate whether the addition of nitrite in physiological concentrations influences the resistance of H pylori to acid.
Methods—H pylori cultured from fresh gastric biopsy specimens was exposed for 30 minutes to normal saline and to HCl/KCl buffer (0.2M) at pH 2 with urea (5 mM) added. The influence of potassium nitrite (50-1000 µmol/l) on bacterial survival was determined.
Results—Addition of nitrite (1 mM) to acidic solutions (pH 2) resulted in complete kill of H pylori within 30 minutes exposure time whereas acid alone allowed the organism to survive (p<0.001). The antimicrobial effect of nitrite at pH 2 against H pylori was dose dependent and complete kill of organisms occurred at concentrations ⩾500 µmol/l.
Conclusion—Acidified nitrite has antibacterial activity against H pylori. This should prompt further research into the effect of salivary nitrite on the survival of H pylori in the human stomach. 



Keywords: nitrite; Helicobacter pylori; acidic conditions

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Figure 1 .

Figure 1

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Antibacterial activity of nitrite against H pylori at pH 2 after 30 minutes' exposure. Experiments were carried out in triplicate (series 1, 2, and 3). No survival was detected at concentrations of nitrite ⩾500 µmol/l. 


Figure 2 .

Figure 2

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pH in universal containers at the end of the experiment versus number of surviving H pylori (starting pH=2 in all experiments). 


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