Effect of Lactobacillus delbrueckii fermented supernatant on Candida albicans biofilm formation

Abstract

Objective To investigate the effect of Lactobacillus delbrueckii fermented supernatant on Candida albicans biofilm and explore its possible mechanism and effective components. Methods Lactobacillus delbrueckii was isolated from vaginal Lactobacillus capsules (Ding Junsheng) and identified by mass spectrometer and sequencing. Lactobacillus delbrueckii fermented supernatant was prepared. The effect of Lactobacillus delbrueckii fermented supernatant on Candida albicans biofilm was tested by microplate crystal violet staining method and catheterization tube modeling method. Biofilm morphological changes were analyzed by crystal violet staining and Live/Dead fluorescent dyes. Exopolysaccharides of Candida albicans biofilm was measured by the sulphruic acid-phenol method. The effect of Lactobacillus delbrueckii fermented supernatant on the adherence of Candida albicans biofilm was tested by the method of colony counting on plate. The fermented supernatant was treated with NaOH, catalase, typsin and proteinase K respectively. Then the treated fermented supernatant′s effect on Candida albicans biofilm formation was detected. One-way ANOVA or Wilcoxon Rank Sum Test was used as statistical analysis for quantitative data. Results Lactobacillus delbrueckii was successfully isolated and identified from Ding Junsheng. Lactobacillus delbrueckii fermented supernatant could significantly and dose-dependantly inhibited the formation of Candida albicans biofilm(F=10.804, P=0.000). The morphological changes showed that the fermented supernatant could decrease the formation of biofilm. When treated with Lactobacillus delbrueckii fermented supernatant, Candida albicans biofilm expolysaccharides was significantly inhibited (F=17.140,P=0.000) and adherence ability was reduced. Compared to untreated fermented supernatant (A490=0.486±0.112), the biofilm inhibition effect of fermented supernatant treated with NaOH (A490=0.675±0.095), catalase (A490=0.577±0.118), typsin (A490=0.600±0.044) and proteinase K (A490=0.495±0.084) only decreased slightly, but when compared to the control group (A490=1.079±0.158), the treated fermented supernatant still showed significant biofilm inhibition effect (χ2=26.052, P=0.000), which suggested that the effective components of fermented supernatant were organic acid and bacteriocin-like substance. Conclusions Lactobacillus delbrueckii fermented supernatant can effectively inhibit Candida albicans biofilm formation. The action mechanisms are related with expolysaccharides decreasement and adherence reduction. The function components of fermented supernatant are possibly organic acids and bacteriocin-like substance. Key words: Candida albicans; Biofilms; Bacterial adhesion; Lactobacillus delbrueckii; Fermentation