Bacterial quorum sensors cross communicate with Candida during biofilm development

Abstract

BACKGROUND: Elucidation of interspecies interactions in mixed biofilms sheds light on the pathophysiology of biofilm induced human infections. OBJECTIVE: To evaluate the effect of bacterial quorum sensing molecules (QSM) on in vitro Candida biofilm formation. METHOD: The effect of QSM of Pseudomonas aeruginosa (N-3-oxo-dodecanoyl-L-Homoserine lactone/C12AHL, N-butyryl-L-Homoserine lactone/C4AHL), and Escherichia coli (Autoinducer-2/AI-2) on six different species of Candida comprising Candida albicans SC 5314, Candida glabrata ATCC 90030, Candida krusei ATCC 6258, Candida tropicalis ATCC 13803, Candida parapsilosis ATCC 22019, Candida dubliniensis MYA 646 was studied using a standard biofilm assay. Biofilm formation of QSM-treated Candida on polystyrene surfaces was quantified by XTT reduction assay. Biofilm structure and the viable biofilm forming cells were analyzed by Confocal Laser Scanning Microscopy (CLSM), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). RESULTS: C12AHL significantly inhibited the adhesion (90min) of C. glabrata, C. dubliniensis and C. krusei, the Initial colonization (24h) of all six Candida spp. and the maturation of all six Candida spp. except C. glabrata (P<0.05). C4AHL significantly inhibited the adhesion (90min) of C. albicans and C. glabrata, the initial colonization (24h) and maturation (48h) of C. albicans, C. glabrata, C. parapsilosis, and C. dubliniensis and the maturation of C. krusei (P<0.05). AI-2 only inhibited C. glabrata adhesion at 90 min. These findings were confirmed by SEM, AFM and CLSM. QSM-treated biofilms showed scanty architecture compared to densely colonized controls. CONCLUSION: Bacterial QSM inhibit in vitro Candida spp. biofilm formation in a time dependent manner. (Supported by HK RGC grant to LPS).