Lactobacillus iners Cell-Free Supernatant Enhances Biofilm Formation and Hyphal/Pseudohyphal Growth by Candida albicans Vaginal Isolates

Abstract

<i>Candida albicans</i> is a commensal fungus of the vaginal mucosa and the principal etiological agent of vaginal candidiasis. Vaginal dysbiosis has been reported during vulvovaginal candidiasis (VVC), with a progressive decrease in <i>Lactobacillus crispatus</i> population and an increase in <i>L. iners</i> population. To date, the role of <i>L. iners</i> in VVC pathogenesis remains scarcely explored. Herein we investigated the in vitro effect of <i>L. iners</i> cell-free supernatant (CFS) on the ability of <i>C. albicans</i> to form biofilms. Biomass and metabolic activity were measured by crystal violet and XTT assays. Further, light microscopy was performed to determine the effect of <i>L. iners</i> CFS on biofilm cellular morphology. We found that <i>L. iners</i> CFS induced a significant increase in biofilm formation by <i>C. albicans</i> clinical isolates which were categorized as moderate or weak biofilm producers. This effect was associated with an enhancement of hyphal/pseudohyphal growth, and the expression levels of <i>HWP1</i> and <i>ECE1</i>, which are typical hyphae-associated genes, were upregulated. Overall, these results suggest that <i>L. iners</i> contributes to the pathogenesis of VVC and highlight the complexity of the interaction between <i>C. albicans</i> and vaginal lactobacilli. Understanding these interactions could prove essential for the development of new strategies for treating VVC.