Effect of vaginal lactobacilli on in vitro growth of Trichomonas vaginalis: Genotyping vaginal lactobacilli and observations on extracellular metabolic dynamics of the lactobacilli and T. vaginalis co-cultures

Abstract

Trichomonas vaginalis is the etiologic agent of the most prevalent non-viral sexually transmitted infection worldwide or trichomoniasis. The establishment of this infection in women is often associated with the abnormal vaginal milieu, which is accompanied with the less acidic vaginal pH and the depletion of the protective commensal vaginal microflora composed of heterogeneous Lactobacillus species. Although it is widely accepted that lactobacilli have probiotic potential and play protective roles against the urogenital pathogens by secretion of broad-spectrum antimicrobial substances, this has not been formally examined in T. vaginalis. We therefore attempted to evaluate the effect of the heterogeneous vaginal Lactobacillus species on the early growth of T. vaginalis in their in vitro coincubation. The aims of this study were: to genotype the isolated Lactobacillus strains of human origins using partial 16S rDNA sequencing and rep-PCR typing method; and to use the genotyped bacterial collection for further evaluation on the effects of the heterogeneous vaginal Lactobacillus isolates over the survival of the parasite in vitro. Metabolic footprinting was also employed to observe the metabolic dynamics of the microbial cultures in order to find the chemotype-to-genotype link of effect of vaginal lactobacilli on growth of trichomonads. The results from coincubation experiments have offered the comprehensive snapshots on the effect of lactobacilli over the early growth of T. vaginalis. Lactobacillus species clearly exhibited their heterogeneous effects on growth of T. vaginalis in microbial cultures. Competitive growth assays of some candidate Lactobacillus strains with T. vaginalis also suggested that the inhibition of bacteria over early growth of trichomonads is not directly related to the mutual exclusive competition. Although the approach used in this study has failed to find an obvious correlation for the probiotic phenotypes and the exometabolome profiles amongst the inhibitive and non-inhibitive Lactobacillus strains, comparing exometabolomes of microbial cultures of closely related Lactobacillus strains have revealed the useful information regarding the specific metabolites that contribute to the differences in inhibitive phenotypes.