Abstract
ABSTRACTBackground: Infections caused by Candida spp. have been associated with formation of a biofilm, i.e. a complex microstructure of cells adhering to a surface and embedded within an extracellular matrix (ECM).Methods: The ECMs of a wild-type (WT, SN425) and two Candida albicans mutant strains, Δ/Δ tec1 (CJN2330) and Δ/Δ efg1 (CJN2302), were evaluated. Colony-forming units (cfu), total biomass (mg), water-soluble polysaccharides (WSPs), alkali-soluble polysaccharides (ASPs), proteins (insoluble part of biofilms and matrix proteins), and extracellular DNA (eDNA) were quantified. Variable-pressure scanning electron microscopy and confocal scanning laser microscopy were performed. The biovolume (μm3/μm2) and maximum thickness (μm) of the biofilms were quantified using COMSTAT2.Results: ASP content was highest in WT (mean ± SD: 74.5 ± 22.0 µg), followed by Δ/Δ tec1 (44.0 ± 24.1 µg) and Δ/Δ efg1 (14.7 ± 5.0 µg). The protein correlated with ASPs (r = 0.666) and with matrix proteins (r = 0.670) in the WT strain. The population in Δ/Δ efg1 correlated with the protein (r = 0.734) and its biofilms exhibited the lowest biomass and biovolume, and maximum thickness. In Δ/Δ tec1, ASP correlated with eDNA (r = 0.678).Conclusion: ASP production may be linked to C. albicans cell filamentous morphology.
Highlights
The members of the genus Candida are opportunistic fungi that are present in the oral cavity
The alkali-soluble polysaccharides (ASPs) data showed significant differences for all of the strains (p = 0.000), with the WT strain possessing the highest amount of this extracellular matrix (ECM) component, followed by Δ/Δ tec1 (44.0 ± 24.1 μg) and Δ/Δ efg1 (14.7 ± 5.0 μg)
Biofilm resistance is multifactorial [33], the protection exerted by the ECM is a key factor in the high levels of antifungal drug resistance displayed by C. albicans biofilms [13,14,34]
Summary
The members of the genus Candida are opportunistic fungi that are present in the oral cavity. Infections caused by Candida spp. are often associated with biofilm formation. A biofilm is a complex microstructure of cells adhering to a surface and embedded within an extracellular matrix (ECM), made up of secreted microbial and host-derived substances (i.e. saliva components) and products of cell lysis [9]. Three classes of conventional antifungals are used for treating infections caused by Candida: azoles (e.g. fluconazole), polyenes (e.g. amphotericin B), and echinocandins (e.g. casponfungin) [11]. Antifungal resistance can arise from all drug classes and includes acquired resistance in susceptible strains and selection of innately less susceptible species [12]. Infections caused by Candida spp. have been associated with formation of a biofilm, i.e. a complex microstructure of cells adhering to a surface and embedded within an extracellular matrix (ECM)
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