Thein vitroeffect of hydrogen peroxide on vaginal microbial communities

Abstract

This study presents a series of experiments carried out in order to elucidate the role of H2O2 in antimicrobial activity of lactobacilli. Vaginal swabs were collected from 60 premenopausal women and checked for pH and Nugent score, and Lactobacillus species were cultured, phenotyped and genotyped. The main outcome measures involved: (1) species of vaginal lactobacilli most effective in liberating H2O2, (2) minimal microbicidal concentrations of added H2O2, (3) kinetics of H2O2 liberation in relation to oxygen tension, (4) antimicrobial activity of pure H2O2 versus one produced by selected vaginal lactobacilli and the total activity of their culture supernatants. Results showed that H2O2 was liberated especially by: Lactobacillus delbrueckii, Lactobacillus acidophilus, Lactobacillus crispatus, Lactobacillus johnsonii and L. gasseri. Hydrogen peroxide reached concentrations from 0.05 to 1.0 mM, which under intensive aeration increased even up to 1.8 mM. Microorganisms related to vaginal pathologies show varied resistance to the action of pure H2O2. Most potent inhibitory activity against bacteria and yeasts was presented by Lactobacillus culture supernate producing H2O2, followed by the nonproducing strain and pure H2O2. To conclude - the antimicrobial activity of lactobacilli is a summation of various inhibitory mechanisms in which H2O2 plays some but not a crucial role, in addition to other substances.

Vaginal pH and Microbicidal Lactic Acid When Lactobacilli Dominate the Microbiota

“…These ‘peroxide-producers’ are associated with a reduced incidence of BV [15,16] and some reproductive tract infections [17,18], compared to ‘non-producing’ lactobacilli. Under permissive in vitro conditions, H 2 O 2 -producing lactobacilli also suppress some reproductive tract pathogens [19,20,21,22]. Together, these observations have led to a general belief that H 2 O 2 production by vaginal lactobacilli provides significant protection against BV-associated bacteria and other reproductive tract pathogens.…”

Cervicovaginal fluid and semen block the microbicidal activity of hydrogen peroxide produced by vaginal lactobacilli

“…Additionally, the vagina is hypoxic most of the time, though the concentration of oxygen in the vagina increases following the insertion of a contraceptive diaphragm, during sexual arousal, and presumably during sexual intercourse [14-16]. Lactobacilli require oxygen to produce hydrogen peroxide: H 2 O 2 concentration is undetectable during anaerobic culture, reaches 29-450 μM during aerobic culture, and 1.0-1.8 mM with vigorous aeration [17-19]. …”

Identification and in vitro production of Lactobacillus antagonists from women with or without bacterial vaginosis

“…Many isolates of vaginal lactobacilli also produce H 2 O 2 , a compound having broad antimicrobial activity. Women colonized by H 2 O 2 -producing lactobacilli have been associated with decreased susceptibility to human immunodeficiency virus (HIV) infection (3) and bacterial vaginosis (BV) (4,5). However, in situ H 2 O 2 production by these lactobacilli has never been demonstrated.…”