Glycerol monolaurate inhibits Candida and Gardnerella vaginalis in vitro and in vivo but not Lactobacillus

Abstract

We investigated the effects of glycerol monolaurate (GML) on Lactobacillus, Candida, and Gardnerella vaginalis human vaginal microflora. Our previous work demonstrated that 6 months of GML treatment vaginally does not alter lactobacillus counts in monkeys. Candida and G. vaginalis are commonly associated with vaginal infections in women, many becoming chronic or recurrent. In vitro growth inhibition studies determined the effects of GML (0 to 500 microg/ml) against multiple Candida species and G. vaginalis. A randomized, double-blind study investigated the effects of GML on vaginal microflora Lactobacillus, Candida, and G. vaginalis in colonized or infected women (n=36). Women self-administered intravaginal gels containing 0% (n=14), 0.5% (n=13), or 5% (n=9) GML every 12 h for 2 days. Vaginal swabs were collected before and immediately after the first gel administration and 12 h after the final gel administration. Swabs were tested for Lactobacillus, Candida, G. vaginalis, and GML. In vitro GML concentrations of 500 microg/ml were candicidal for all species tested, while a concentration of 10 microg/ml was bactericidal for G. vaginalis. Control and GML gels applied vaginally in women did not alter vaginal pH or Lactobacillus counts. Control gels reduced G. vaginalis counts but not Candida counts, whereas GML gels reduced both Candida and G. vaginalis. No adverse events were reported by participating women. GML is antimicrobial for Candida and G. vaginalis in vitro. Vaginal GML gels in women do not affect Lactobacillus negatively but significantly reduce Candida and G. vaginalis.

FIG. 1.

In vitro effect of GML on the growth of Candida species: C. albicans (A), C. glabrata (B), C. pseudotropicalis (kefyr) (C), C. parapsilosis (D), C. tropicalis (E), and C. krusei (F). Candida strains were incubated for 24 h in the presence of various concentrations of GML at 37°C. Samples were removed at the indicated times for determination of CFU counts. The GML concentrations were 0 μg/ml (▪), 50 μg/ml (□), 100 μg/ml (▴), and 500 μg/ml (▵).

FIG. 2.

In vitro effect of GML on the growth of G. vaginalis. G. vaginalis was cultured for 24 h in the presence of various concentrations of GML at 37°C. Samples were removed at the indicated times for determination of CFU counts. The GML concentrations included 0 μg/ml (▪), 1 μg/ml (□), 5 μg/ml (▴), and 10 μg/ml (▵).