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 pathog

Abstract

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.

Antimicrobial properties of probiotic strains isolated from breast-fed infants

“…Coaggregation of bacteria with harmful microorganisms has been considered as a protective mechanism against infection (Collado et al, 2008), and has been described in Lactobacillus (Pascual et al, 2008) and in Bifidobacterium (Del Re et al, 2000;Vlková , Rada, Smehilová , & Killer, 2008) from human origin. The mechanism underlying the protective activity of certain beneficial strains against bacterial pathogens appears to be multifactorial, where a co-operative antimicrobial effect might be considered (Atassi & Servin, 2010).…”

Anti-Infective Activities of Lactobacillus Strains in the Human Intestinal Microbiota: from Probiotics to Gastrointestinal Anti-Infectious Biotherapeutic Agents

“…The antimicrobial effect of lactic acid is not just due to the lowering of the intracellular pH. Indeed, hydrogen peroxide produced by L. johnsonii NCC 533 and other L. johnsonii strains in vitro kills S. Typhimurium (133), an effect enhanced in the presence of the membrane permeabilizer lactic acid (132). As deduced from in vitro experiments that have tested the sensitivities of secreted compounds present in L. rhamnosus GG, L. johnsonii NCC 533, and L. acidophilus LB CFCSs to a set of physical and chemical treatments and from partial isolation experiments, bactericidal activity against S. Typhimurium results from small (dialysis cutoff, 1,000 Da), nonproteinaceous compounds (120,122,123).…”

Bacteriocin Production: a Probiotic Trait?

“…Indeed, the production of antimicrobials is often regarded a priori as an important trait in the context of bacterial fitness but also in terms of probiotic efficacy. Several probiotic bacteria produce a variety of antimicrobial compounds (e.g., short-chain fatty acids, hydrogen peroxide, nitric oxide, bacteriocins) that may enhance their ability to compete against other GI microbes and which could potentially inhibit pathogenic (disease-causing) bacteria (1,6). Traditionally, bacteriocin production has been an important criterion in the selection of a probiotic strain, albeit that few studies have definitively demonstrated the impact of bacteriocin production on the ability of a strain to compete within the GI tract and/or positively influence the health of the host (9).…”