A synthetic killer peptide impairs Candida albicans biofilm formation and persistence in vitro

Introduction. Candida spp. colonize human skin and mucosae of healthy subjects, behaving as harmless commensals. Nevertheless, in susceptible patients (with medical devices or immunosuppressed), they behave as opportunistic pathogens also because of their capacity to form biofilms on mucosae or medical devices. Indeed, when embedded in a biofilm, Candida cells become more resistant to common disinfectants and most antifungal, including azoles. Thus, there is an urgent need to identify novel therapeutic molecules. Recently, several antibody-derived peptides have been shown to have antimicrobial, antiviral, immunomodulatory and antitumor activity both in vitro and in vivo. The aim of this study was to investigate the effect of a synthetic killer peptide (KP), on the formation and persistence of Candida biofilm. Materials and Methods. The reference strain C. albicans SC5314, two C. albicans fluconazole-resistant and two C. albicans fluconazole-susceptible isolates were employed. Together with a scrambled peptide, used as negative control, the KP (AKVTMTCSAS) was tested against Candida biofilm at different stage of development, by microscopy, crystal violet and tetrazolium salt reduction assays. Results. The KP strongly influenced the capacity of Candida albicans to form biofilm and significantly impairs preformed mature biofilm. KP treatment resulted in an increase in Candida oxidative stress response and membrane permeability; moreover, biofilm-related genes expression was markedly reduced. Similar inhibitory effects were observed against all the strains tested, irrespective of their resistance or susceptibility to the drug. Interestingly, the KP-mediated inhibitory effect was shown even against a catheter-associated C. albicans biofilm. Conclusions. These results provide the first evidence of the effects of KP against C. albicans biofilm, suggesting that this peptide may represent a novel potential molecule for treatment and prevention of biofilm-related C. albicans infections.