AUTHOR=Poon Yeuklan , Hui Mamie 

TITLE=Inhibitory effect of lactobacilli supernatants on biofilm and filamentation of Candida albicans, Candida tropicalis, and Candida parapsilosis

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1105949

DOI=10.3389/fmicb.2023.1105949

ISSN=1664-302X

ABSTRACT=<sec><title>Introduction</title><p>Probiotic <italic>Lactobacillus</italic> strains had been investigated for the potential to protect against infection caused by the major fungal pathogen of human, <italic>Candida albicans</italic>. Besides antifungal activity, lactobacilli demonstrated a promising inhibitory effect on biofilm formation and filamentation of <italic>C. albicans</italic>. On the other hand, two commonly isolated non-albicans <italic>Candida</italic> species, <italic>C. tropicalis</italic> and <italic>C. parapsilosis</italic>, have similar characteristics in filamentation and biofilm formation with <italic>C. albicans</italic>. However, there is scant information of the effect of lactobacilli on the two species.</p></sec><sec><title>Methods</title><p>In this study, biofilm inhibitory effects of <italic>L. rhamnosus</italic> ATCC 53103, <italic>L. plantarum</italic> ATCC 8014, and <italic>L. acidophilus</italic> ATCC 4356 were tested on the reference strain <italic>C. albicans</italic> SC5314 and six bloodstream isolated clinical strains, two each of <italic>C. albicans</italic>, <italic>C. tropicalis</italic>, and <italic>C. parapsilosis</italic>.</p></sec><sec><title>Results and Discussion:</title><p>Cell-free culture supernatants (CFSs) of <italic>L. rhamnosus</italic> and <italic>L. plantarum</italic> significantly inhibited <italic>in vitro</italic> biofilm growth of <italic>C. albicans</italic> and <italic>C. tropicalis</italic>. <italic>L. acidophilus</italic>, conversely, had little effect on <italic>C. albicans</italic> and <italic>C. tropicalis</italic> but was more effective on inhibiting <italic>C. parapsilosis</italic> biofilms. Neutralized <italic>L. rhamnosus</italic> CFS at pH 7 retained the inhibitory effect, suggesting that exometabolites other than lactic acid produced by the <italic>Lactobacillus</italic> strain might be accounted for the effect. Furthermore, we evaluated the inhibitory effects of <italic>L. rhamnosus</italic> and <italic>L. plantarum</italic> CFSs on the filamentation of <italic>C. albicans</italic> and <italic>C. tropicalis</italic> strains. Significantly less <italic>Candida</italic> filaments were observed after co-incubating with CFSs under hyphae-inducing conditions. Expressions of six biofilm-related genes (<italic>ALS1</italic>, <italic>ALS3</italic>, <italic>BCR1</italic>, <italic>EFG1</italic>, <italic>TEC1</italic>, and <italic>UME6</italic> in <italic>C. albicans</italic> and corresponding orthologs in <italic>C. tropicalis</italic>) in biofilms co-incubated with CFSs were analyzed using quantitative real-time PCR. When compared to untreated control, the expressions of <italic>ALS1</italic>, <italic>ALS3</italic>, <italic>EFG1</italic>, and <italic>TEC1</italic> genes were downregulated in <italic>C. albicans</italic> biofilm. In <italic>C. tropicalis</italic> biofilms, <italic>ALS3</italic> and <italic>UME6</italic> were downregulated while <italic>TEC1</italic> was upregulated. Taken together, the <italic>L. rhamnosus</italic> and <italic>L. plantarum</italic> strains demonstrated an inhibitory effect, which is likely mediated by the metabolites secreted into culture medium, on filamentation and biofilm formation of <italic>C. albicans</italic> and <italic>C. tropicalis</italic>. Our finding suggested an alternative to antifungals for controlling <italic>Candida</italic> biofilm.</p></sec>