Fluconazole impacts the extracellular matrix of fluconazole-susceptible and -resistant Candida albicans and Candida glabrata biofilms

Abstract

Background: Fluconazole (FLZ) is a drug commonly used for the treatment of Candida infections. However, β-glucans in the extracellular matrices (ECMs) hinder FLZ penetration into Candida biofilms, while extracellular DNA (eDNA) contributes to the biofilm architecture and resistance. Methods: This study characterized biofilms of FLZ-sensitive (S) and -resistant (R) Candida albicans and Candida glabrata in the presence or absence of FLZ focusing on the ECM traits. Biofilms of C. albicans American Type Culture Collection (ATCC) 90028 (CaS), C. albicans ATCC 96901 (CaR), C. glabrata ATCC 2001 (CgS), and C. glabrata ATCC 200918 (CgR) were grown in RPMI medium with or without FLZ at 5× the minimum inhibitory concentration (37°C/48 h). Biofilms were assessed by colony-forming unit (CFU)/mL, biomass, and ECM components (alkali-soluble polysaccharides [ASP], water-soluble polysaccharides [WSP], eDNA, and proteins). Scanning electron microscopy (SEM) was also performed. Data were analyzed by parametric and nonparametric tests (α = 0.05). Results: In biofilms, FLZ reduced the CFU/mL of all strains (p < 0.001), except for CaS (p = 0.937). However, the ASP quantity in CaS was significantly reduced by FLZ (p = 0.034), while the drug had no effect on the ASP levels in other strains (p > 0.05). Total biomasses and WSP were significantly reduced by FLZ in the ECM of all yeasts (p < 0.001), but levels of eDNA and proteins were unaffected (p > 0.05). FLZ affected the cell morphology and biofilm structure by hindering hyphae formation in CaS and CaR biofilms, by decreasing the number of cells in CgS and CgR biofilms, and by yielding sparsely spaced cell agglomerates on the substrate. Conclusion: FLZ impacts biofilms of C. albicans and C. glabrata as evident by reduced biomass. This reduced biomass coincided with lowered cell numbers and quantity of WSPs. Hyphal production by C. albicans was also reduced.

Evaluation of the Antifungal Activity of the Licania Rigida Leaf Ethanolic Extract against Biofilms Formed by Candida Sp. Isolates in Acrylic Resin Discs

“…In our study, there were significant differences in the treatment of biofilms formed by three strains treated with this antifungal. Although a reduction in biofilm biomass was observed with fluconazole treatment in the present study, resistance to this drug is increasing among Candida species [26,27].…”

“…This may be due to the characteristics of isolates that are not shared by the species. Moreover, a C. albicans biofilm biomass reduction has been demonstrated in previous studies [26,30].…”

“…Fluconazole is the commonly used drug to treat Candida infections, where its action on biofilms has been reported [26]. In our study, there were significant differences in the treatment of biofilms formed by three strains treated with this antifungal.…”

Role of major facilitator superfamily transporter Qdr2p in biofilm formation by Candida glabrata

“…Typically, if the minimum inhibitory concentration which inhibits 90% of cells growth (MIC 90 ) is higher than 64 μg/mL, it indicates that the fungal shows drug resistance phenotype towards fluconazole . Meanwhile, recent reports showed that due to the formation of biofilm and the natural azole‐resistant characteristic of C glabrata , the FLC minimum biofilm eradicatory concentrations (MBEC) of C glabrata might be higher than 1250 μg/mL . We verified the biofilm structural differences as a result of QDR2 deletion through SEM observation.…”

“…34,35 Meanwhile, recent reports showed that due to the formation of biofilm and the natural azole-resistant characteristic of C glabrata, the FLC minimum biofilm eradicatory concentrations (MBEC) of C glabrata might be higher than 1250 μg/mL. 36,37 We verified the biofilm structural differences as a result of QDR2 deletion through SEM observation. Notably, ∆qdr2 biofilms were noticeably fragile and scattered (data not shown) with decreased ECM (Figure 2); this decrease in the ECM may result in increased permeability of the ∆qdr2 biofilm to FLC.…”