title: Helicobacter pylori is killed by nitrite under acidic conditions.
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.
  
  
  OBJECTIVE
  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 mumol/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 > or = 500 mumol/l.
  
  
  CONCLUSIONS
  Acidified nitrite has anti-bacterial 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.
authors.affiliation: Department of Medicine and Therapeutics, Medical School, Forresterhill, Aberdeen, UK.
authors.forename: R S
authors.initials: RS
authors.lastname: Dykhuizen
authors.forename: A
authors.initials: A
authors.lastname: Fraser
authors.forename: H
authors.initials: H
authors.lastname: McKenzie
authors.forename: M
authors.initials: M
authors.lastname: Golden
authors.forename: C
authors.initials: C
authors.lastname: Leifert
authors.forename: N
authors.initials: N
authors.lastname: Benjamin
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001431:Bacteriological Techniques; D016480:Helicobacter pylori / Q000187:drug effects*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009573:Nitrites / Q000494:pharmacology*; D014508:Urea / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D009573:Nitrites; D014508:Urea