Alginate oligosaccharides enhance the antifungal activity of nystatin against candidal biofilms

Abstract

BackgroundThe increasing prevalence of invasive fungal infections in immuno-compromised patients is a considerable cause of morbidity and mortality. With the rapid emergence of antifungal resistance and an inadequate pipeline of new therapies, novel treatment strategies are now urgently required.MethodsThe antifungal activity of the alginate oligosaccharide OligoG in conjunction with nystatin was tested against a range of Candida spp. (C. albicans, C. glabrata, C. parapsilosis, C. auris, C. tropicalis and C. dubliniensis), in both planktonic and biofilm assays, to determine its potential clinical utility to enhance the treatment of candidal infections. The effect of OligoG (0-6%) ± nystatin on Candida spp. was examined in minimum inhibitory concentration (MIC) and growth curve assays. Antifungal effects of OligoG and nystatin treatment on biofilm formation and disruption were characterized using confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM) and ATP cellular viability assays. Effects on the cell membrane were determined using permeability assays and transmission electron microscopy (TEM).ResultsMIC and growth curve assays demonstrated the synergistic effects of OligoG (0-6%) with nystatin, resulting in an up to 32-fold reduction in MIC, and a significant reduction in the growth of C. parapsilosis and C. auris (minimum significant difference = 0.2 and 0.12 respectively). CLSM and SEM imaging demonstrated that the combination treatment of OligoG (4%) with nystatin (1 µg/ml) resulted in significant inhibition of candidal biofilm formation on glass and clinical grade silicone surfaces (p < 0.001), with increased cell death (p < 0.0001). The ATP biofilm disruption assay demonstrated a significant reduction in cell viability with OligoG (4%) alone and the combined OligoG/nystatin (MIC value) treatment (p < 0.04) for all Candida strains tested. TEM studies revealed the combined OligoG/nystatin treatment induced structural reorganization of the Candida cell membrane, with increased permeability when compared to the untreated control (p < 0.001).ConclusionsAntimicrobial synergy between OligoG and nystatin against Candida spp. highlights the potential utility of this combination therapy in the prevention and topical treatment of candidal biofilm infections, to overcome the inherent tolerance of biofilm structures to antifungal agents.

Vaginal prevention of Candida albicans: synergistic effect of lactobacilli and mannan oligosaccharides (MOS)

“…Despite literature studies on the antifungal activity of MOS is scarce, other oligosaccharides such as chitosan and alginate oligosaccharides have been studied and demonstrated antifungal activity against Candida sp. (Ganan et al 2019 ; Powell et al 2023 ).…”

Died or Not Dyed: Assessment of Viability and Vitality Dyes on Planktonic Cells and Biofilms from Candida parapsilosis

“…However, S9 and FDA are commonly used in studies of antimicrobial efficacy on the planktonic and biofilm cells of Candida spp. without the use of cell visualization controls [ 14 , 15 , 16 , 17 , 18 , 19 ]. Moreover, TO is used in cell viability analysis by flow cytometry [ 20 , 21 ], where it is easier to miss the presence of permeability issues.…”

“…Four different dyes commonly used for yeast staining [ 16 , 17 , 20 , 34 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ], two for cell viability and two for cell vitality, were selected. Additionally, the chitin dye CW (Thermo Fisher Scientific, Carlsbad, CA, USA) at 10 μM was used as the control for cell visualization.…”

The inhibitory effects of carvacrol, nystatin, and their combination on oral candidiasis isolates

“…Our results indicated that carvacrol, particularly when combined with nystatin, significantly reduced the MIC against Candida, suggesting its potential as an effective, low-dose treatment option. In 2023, Powell et al [31] reported that alginate oligosaccharides enhanced the antifungal activity of nystatin against Candida biofilms, leading to an up to 32-fold reduction in MIC. Additionally, the MTT test results indicated that carvacrol significantly inhibits the growth of Candida species, more effectively than nystatin.…”