Isolation of Vaginal Lactobacilli and Characterization of Anti-Candida Activity

Abstract

Healthy vaginal microbiota is dominated by Lactobacillus spp., which form a critical line of defence against pathogens, including Candida spp. The present study aims to identify vaginal lactobacilli exerting in vitro activity against Candida spp. and to characterize their antifungal mechanisms of action. Lactobacillus strains were isolated from vaginal swabs of healthy premenopausal women. The isolates were taxonomically identified to species level (L. crispatus B1-BC8, L. gasseri BC9-BC14 and L. vaginalis BC15-BC17) by sequencing the 16S rRNA genes. All strains produced hydrogen peroxide and lactate. Fungistatic and fungicidal activities against C. albicans, C. glabrata, C. krusei, C. tropicalis, C. parapsilosis and C. lusitaniae were evaluated by broth micro-dilution method. The broadest spectrum of activity was observed for L. crispatus BC1, BC4, BC5 and L. vaginalis BC15, demonstrating fungicidal activity against all isolates of C. albicans and C. lusitaniae. Metabolic profiles of lactobacilli supernatants were studied by 1H-NMR analysis. Metabolome was found to be correlated with both taxonomy and activity score. Exclusion, competition and displacement experiments were carried out to investigate the interference exerted by lactobacilli toward the yeast adhesion to HeLa cells. Most Lactobacillus strains significantly reduced C. albicans adhesion through all mechanisms. In particular, L. crispatus BC2, L. gasseri BC10 and L. gasseri BC11 appeared to be the most active strains in reducing pathogen adhesion, as their effects were mediated by both cells and supernatants. Inhibition of histone deacetylases was hypothesised to support the antifungal activity of vaginal lactobacilli. Our results are prerequisites for the development of new therapeutic agents based on probiotics for prophylaxis and adjuvant therapy of Candida infection.

Antimicrobial Compounds Produced by Vaginal Lactobacillus crispatus Are Able to Strongly Inhibit Candida albicans Growth, Hyphal Formation and Regulate Virulence-related Gene Expressions

“…A microplate assay was used to evaluate the antimicrobial activity of the CFS against C. albicans according to Parolin et al (2015) with some modifications. A mixture of 100 μL C. albicans suspensions in YPD broth (∼10 6 CFU/mL) and 100 μL tested CFS was added to each well of a sterile 96-well microplate (Costar 3799, Corning, NY, USA).…”

Fungi at the Scene of the Crime: Innocent Bystanders or Accomplices in Oral Infections?

“…Discovery of C. albicans and Lactobacillus species in denture plaques was unexpected, as these bacteria have previously displayed antagonism with C. albicans at other mucosal sites [87]. The interactions and mechanisms employed by C. albicans and Lactobacilli remain somewhat enigmatic.…”

Selection of Lactobacillus strains as potential probiotics for vaginitis treatment

“…However, in cases of dysbiosis, where there is a reduction in the population of lactobacilli, it is expected that exogenous probiotics would be able to compete for the same receptors and/or promote displacement of pathogens already adhered. et Castro et al, 2013;Parolin et al, 2015). These interference abilities were tested for Lactobacillus cultures, bacterial cells resuspended in fresh MRS medium and culture cell-free supernatants.…”