title: Acidic conditions enhance bactericidal effects of sodium bisulfite on Helicobacter pylori.
abstract: BACKGROUND
  The Brucella broth medium, which is often used for the cultivation of microaerobic bacteria including Helicobacter pylori. It contains sodium bisulfite to decrease oxygen content in the medium. The growth of H. pylori, however, is inhibited by sodium bisulfite. In this study, the effect of sodium bisulfite was compared with several antioxidants and quantified under acidic conditions, mimicking the gastric environment.
  
  
  METHODS
  Growth of H. pylori in the presence of several antioxidants was evaluated at OD655 nm. Effect of sodium bisulfite on H. pylori under acidic conditions was evaluated by measuring colony forming units (cfu).
  
  
  RESULTS
  Under neutral conditions, sodium bisulfite was a more potent suppressor of H. pylori. Resveratrol, a polyphenol found in wine, exhibited the most potent inhibitory activity. To quantify the effect of sodium bisulfite on H. pylori under acidic conditions, the bacteria were grown at 37 degrees C for 30 minutes in 0.15 mol/l HCl/KCl (pH 2.0) with or without urea and sodium bisulfite. Sodium bisulfite (0.5 mmol/l) did not affect the viability at neutral pH 7.0, however, it killed H. pylori under acidic conditions, even if urea, the key substance enabling H. pylori to survive under acidic conditions, was present. The bacteria, which had been incubated under acidic conditions in the presence of urea, could survive a subsequent 30 minute-incubation at pH 2.0 without urea. Presence of sodium bisulfite, however, in the subsequent 30 minute-incubation, killed the bacteria.
  
  
  CONCLUSIONS
  The bactericidal effect of sodium bisulfite on H. pylori was greater under acidic conditions and independent of urease activity.
authors.affiliation: Department of Clinical Molecular Biology, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku Chiba, 260-8670, Japan.
authors.forename: Akiyuki
authors.initials: A
authors.lastname: Murano
authors.forename: Naoko
authors.initials: N
authors.lastname: Morinaga
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Iwamaru
authors.forename: Kinnosuke
authors.initials: K
authors.lastname: Yahiro
authors.forename: Motoyuki
authors.initials: M
authors.lastname: Tagashira
authors.forename: Joel
authors.initials: J
authors.lastname: Moss
authors.forename: Hideki
authors.initials: H
authors.lastname: Tanzawa
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Noda
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology; D000975:Antioxidants / Q000494:pharmacology; D003470:Culture Media; D016480:Helicobacter pylori / Q000187:drug effects / Q000254:growth & development*; D006863:Hydrogen-Ion Concentration; D013447:Sulfites / Q000494:pharmacology; D014508:Urea
chemical_list: D000890:Anti-Infective Agents; D000975:Antioxidants; D003470:Culture Media; D013447:Sulfites; D014508:Urea; C009279:sodium bisulfite