Under conditions closely mimicking vaginal fluid, Lactobacillus jensenii strain 62B produces a bacteriocin-like inhibitory substance that targets and eliminates Gardnerella species

Abstract

Within the vaginal ecosystem, lactobacilli and Gardnerella spp. likely interact and influence each other’s growth, yet the details of this interaction are not clearly defined. Using medium simulating vaginal fluid and a two-chamber co-culturing system to prevent cell-to-cell contact between the bacteria, we examined the possibility that Lactobacillus jensenii 62B (Lj 62B) and/or G. piotii (Gp) JCP8151B produce extracellular factors through which they influence each other’s viability. By 24 h post-inoculation (hpi) in the co-culture system and under conditions similar to the vaginal environment – pH 5.0, 37 °C, and 5% CO2, Lj 62B viability was not affected but Gp JCP8151B had been eliminated. Cell-free supernatant harvested from Lj 62B cultures (Lj-CFS) at 20 hpi, but not 16 hpi, also eliminated Gp JCP8151B growth. Neither lactic acid nor H2O2 production by Lj 62B was responsible for this effect. The Lj-CFS did not affect viability of three species of lactobacilli or eight species of Gram-positive and Gram-negative uropathogens but eliminated viability of eight different strains of Gardnerella spp. Activity of the inhibitory factor within Lj-CFS was abolished by protease treatment and reduced by heat treatment suggesting it is most likely a bacteriocin-like protein; fractionation revealed that the factor has a molecular weight within the 10–30 kDa range. These results suggest that, in medium mimicking vaginal fluid and growth conditions similar to the vaginal environment, Lj 62B produces a potential bacteriocin-like inhibitory substance (Lj-BLIS) that clearly targets Gardnerella spp. strains. Once fully characterized, Lj-BLIS may be a potential treatment for Gardnerella-related BV that does not alter the vaginal microflora.

Evidence of Lactobacillus strains shared between the female urinary and vaginal microbiota

“…Communities dominated by lactobacilli are frequently associated with 'health' or lack of symptoms [3,4]. Lactobacillus strains isolated from female urogenital samples have routinely exhibited antimicrobial properties [5][6][7][8][9][10][11], suggesting that they play a role in inhibiting or killing pathogens in the urinary tract and/or vagina. Studies of the healthy (asymptomatic) bladder microbiome have shown that it is frequently predominated by lactobacilli [2].…”

“…L. iners, L. gasseri, and L. jensenii have frequently been observed within the urinary microbiome of females with incontinence [2,3,18]. Nevertheless, L. gasseri and L. jensenii have been found to be effective in inhibiting the growth of several urogenital pathogens [11,19].…”