Antifungal Activity Assessment of Postbiotic Mediators Derived From Lactobacillus rhamnosus GG and Lactobacillus reuteri Against Candida albicans

Abstract

The rise of antimicrobial resistance has increased interest in safe alternative therapeutic agents, including postbiotic mediators (PMs), which are sterile, cell-free, filter-sterilized preparations derived from probiotics. This study investigated the antifungal and antibiofilm activity of PMs derived from Lactobacillus rhamnosus GG (LGG) and Lactobacillus reuteri (LR) against Candida albicans, an opportunistic pathogen implicated in oral infections. PMs were prepared from LGG and LR cultures. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) against C. albicans were determined using broth microdilution and colony-forming unit (CFU) counts. Antibiofilm activity at sub-MIC concentrations was evaluated by assessing metabolic activity (XTT assay) and biofilm architecture (scanning electron microscopy, SEM). The MIC and MFC of PMs from both LGG and LR were 25% (v/v). Both PMs significantly reduced the metabolic activity of C. albicans biofilms as measured by the XTT assay (p ≤ 0.002); however, a statistically significant reduction in viable biofilm counts was observed only with LGG PMs (p = 0.0038), whereas LR PMs showed a non-significant reduction (p = 0.1537). SEM showed marked changes in biofilm architecture. PMs from LGG and LR showed in vitro antifungal activity against C. albicans, with both preparations suppressing biofilm metabolic activity and LGG PMs additionally producing a statistically significant reduction in viable biofilm counts. These findings support further investigation of Lactobacillus-derived PMs as candidate adjunctive antifungal approaches; however, validation in clinical and antifungal-resistant isolates, chemical and mechanistic characterization, cytotoxicity testing, and in vivo studies are required before clinical application.