Individual and co-operative roles of lactic acid and hydrogen peroxide in the killing activity of enteric strain Lactobacillus johnsonii NCC933 and vaginal strain Lactobacillus gasseri KS120.1 against enteric, uropathogenic and vaginosis-associated pathogens

FEMS Microbiol Lett. 2010 Mar;304(1):29-38. doi: 10.1111/j.1574-6968.2009.01887.x. Epub 2009 Dec 24.


The mechanism underlying the killing activity of Lactobacillus strains against bacterial pathogens appears to be multifactorial. Here, we investigate the respective contributions of hydrogen peroxide and lactic acid in killing bacterial pathogens associated with the human vagina, urinary tract or intestine by two hydrogen peroxide-producing strains. In co-culture, the human intestinal strain Lactobacillus johnsonii NCC933 and human vaginal strain Lactobacillus gasseri KS120.1 strains killed enteric Salmonella enterica serovar Typhimurium SL1344, vaginal Gardnerella vaginalis DSM 4944 and urinary tract Escherichia coli CFT073 pathogens. The cell-free culture supernatants (CFCSs) produced the same reduction in SL1344, DSM 4944 and CFT073 viability, whereas isolated bacteria had no effect. The killing activity of CFCSs was heat-stable. In the presence of Dulbecco's modified Eagle's minimum essential medium inhibiting the lactic acid-dependent killing activity, CFCSs were less effective at killing of the pathogens. Catalase-treated CFCSs displayed a strong decreased activity. Tested alone, hydrogen peroxide triggered a concentration-dependent killing activity against all three pathogens. Lactic acid alone developed a killing activity only at concentrations higher than that present in CFCSs. In the presence of lactic acid at a concentration present in Lactobacillus CFCSs, hydrogen peroxide displayed enhanced killing activity. Collectively, these results demonstrate that for hydrogen peroxide-producing Lactobacillus strains, the main metabolites of Lactobacillus, lactic acid and hydrogen peroxide, act co-operatively to kill enteric, vaginosis-associated and uropathogenic pathogens.

MeSH terms

  • Anti-Bacterial Agents / metabolism
  • Anti-Bacterial Agents / pharmacology
  • Antibiosis*
  • Drug Synergism
  • Enterobacteriaceae / classification
  • Enterobacteriaceae / growth & development
  • Enterobacteriaceae / metabolism
  • Female
  • Gardnerella vaginalis / drug effects
  • Gardnerella vaginalis / growth & development
  • Humans
  • Hydrogen Peroxide* / metabolism
  • Hydrogen Peroxide* / pharmacology
  • Lactic Acid* / metabolism
  • Lactic Acid* / pharmacology
  • Lactobacillus* / classification
  • Lactobacillus* / growth & development
  • Lactobacillus* / metabolism
  • Salmonella Infections / microbiology
  • Salmonella Infections / prevention & control
  • Salmonella typhimurium* / drug effects
  • Salmonella typhimurium* / growth & development
  • Urinary Tract Infections / microbiology
  • Urinary Tract Infections / prevention & control
  • Uropathogenic Escherichia coli* / drug effects
  • Uropathogenic Escherichia coli* / growth & development
  • Vagina / microbiology
  • Vaginosis, Bacterial / microbiology
  • Vaginosis, Bacterial / prevention & control


  • Anti-Bacterial Agents
  • Lactic Acid
  • Hydrogen Peroxide