Inhibitory effect of lactobacilli supernatants on biofilm and filamentation of , , and .

INTRODUCTION

Probiotic strains had been investigated for the potential to protect against infection caused by the major fungal pathogen of human, . Besides antifungal activity, lactobacilli demonstrated a promising inhibitory effect on biofilm formation and filamentation of . On the other hand, two commonly isolated non-albicans species, and , have similar characteristics in filamentation and biofilm formation with . However, there is scant information of the effect of lactobacilli on the two species.

METHODS

In this study, biofilm inhibitory effects of ATCC 53103, ATCC 8014, and ATCC 4356 were tested on the reference strain SC5314 and six bloodstream isolated clinical strains, two each of , , and .

RESULTS AND DISCUSSION

Cell-free culture supernatants (CFSs) of and significantly inhibited biofilm growth of and . , conversely, had little effect on and but was more effective on inhibiting biofilms. Neutralized CFS at pH 7 retained the inhibitory effect, suggesting that exometabolites other than lactic acid produced by the strain might be accounted for the effect. Furthermore, we evaluated the inhibitory effects of and CFSs on the filamentation of and strains. Significantly less filaments were observed after co-incubating with CFSs under hyphae-inducing conditions. Expressions of six biofilm-related genes (, , , , , and in and corresponding orthologs in ) in biofilms co-incubated with CFSs were analyzed using quantitative real-time PCR. When compared to untreated control, the expressions of , , , and genes were downregulated in biofilm. In biofilms, and were downregulated while was upregulated. Taken together, the and strains demonstrated an inhibitory effect, which is likely mediated by the metabolites secreted into culture medium, on filamentation and biofilm formation of and . Our finding suggested an alternative to antifungals for controlling biofilm.