Antifungal activity of cathelicidin peptides against planktonic and biofilm cultures of Candida species isolated from vaginal infections

Vulvovaginal candidiasis (VVC) is a frequent gynecological condition caused by Candida albicans and afew non-albicans Candida spp. It has a significant impact on the quality of life of the affected womenalso due to a considerable incidence of recurrent infections that are difficult to treat. The formation offungal biofilm may contribute to the problematic management of recurrent VVC due to the intrinsicresistance of sessile cells to the currently available antifungals. Thus, alternative approaches for theprevention and control of biofilm-related infections are urgently needed. In this regard, the cationicantimicrobial peptides (AMPs) of the innate immunity are potential candidates for the development ofnovel antimicrobials as many of them display activity against biofilm formed by various microbial species.In the present study, we investigated the in vitro antifungal activities of the cathelicidin peptides LL-37and BMAP-28 against pathogenic Candida spp. also including C. albicans, isolated from vaginal infections,and against C. albicans SC5314 as a reference strain. The antimicrobial activity was evaluated againstplanktonic and biofilm-grown Candida cells by using microdilution susceptibility and XTT [2,3-bis(2-methoxy-4-nitro-5-sulfo-phenyl)-2H-tetrazolium-5-carboxanilide] reduction assays and, in the case ofestablished biofilms, also by CFU enumeration and fluorescence microscopy. BMAP-28 was effectiveagainst planktonically grown yeasts in standard medium (MIC range, 2–32 M), and against isolatesof C. albicans and Candida krusei in synthetic vaginal simulated fluid (MIC range 8–32 M, dependingon the pH of the medium). Established 48-h old biofilms formed by C. albicans SC5314 and C. albicansand C. krusei isolates were 70–90% inhibited within 24 h incubation with 16 M BMAP-28. As shownby propidium dye uptake and CFU enumeration, BMAP-28 at 32 M killed sessile C. albicans SC5314by membrane permeabilization with a faster killing kinetics compared to 32 M miconazole (80–85%reduced biofilm viability in 90 min vs 48 h). In addition, BMAP-28 at 16 M prevented Candida biofilmformation on polystyrene and medical grade silicone surfaces by causing a >90% reduction in the viabilityof planktonic cells in 30 min. LL-37 was overall less effective than BMAP-28 against planktonic Candidaspp. (MIC range 4–≥64 M), and was ineffective against established Candida biofilms. However, LL-37 at64 M prevented Candida biofilm development by inhibiting cell adhesion to polystyrene and siliconesurfaces. Finally, Candida adhesion was strongly inhibited when silicone was pre-coated with a layerof BMAP-28 or LL-37, encouraging further studies for the development of peptide-based antimicrobialcoatings.© 2015 Elsevier Inc. All rights reserved