Abstract
Candida glabrata biofilms are recognized to have high resistance to antifungals. In order to understand the effect of mannans in the resistance profile of C. glabrata mature biofilms, C. glabrata Δmnn2 was evaluated. Biofilm cell walls were analysed by confocal laser scanning microscopy (CLSM) and their susceptibility was assessed for fluconazole, amphotericin B, caspofungin, and micafungin. Crystal violet and Alcian Blue methods were performed to quantify the biomass and the mannans concentration in the biofilm cells and matrices, respectively. The concentration of β-1,3 glucans was also measured. No visible differences were detected among cell walls of the strains, but the mutant had a high biomass reduction, after a drug stress. When compared with the reference strain, it was detected a decrease in the susceptibility of the biofilm cells and an increase of β-1,3 glucans in the C. glabrata Δmnn2. The deletion of the MNN2 gene in C. glabrata induces biofilm matrix and cell wall variabilities that increase the resistance to the antifungal drug treatments. The rise of β-1,3 glucans appears to have a role in this effect.
Highlights
In opposition to Candida albicans and other Candida species, Candida glabrata grows only as blastoconidia, and has a haploid genome [1]
Fungal diseases associated with non-Candida albicans Candida (NCAC) species have been globally increasing [3,4]
The images of the 48-h-biofilms of C. glabrata ATCC2001, C. glabrata ∆mnn2, and C. glabrata ∆HT6 showed that the gene deletion, apparently, had no effect on the cell wall, since there were no relevant differences among the three strains (Figure 1)
Summary
In opposition to Candida albicans and other Candida species, Candida glabrata grows only as blastoconidia, and has a haploid genome [1]. Despite being a part of the natural human microflora, under circumstances where the host immune system becomes severely compromised (e.g., chemotherapy, traumas), C. glabrata can invade epithelial cells, disseminating via the bloodstream, causing systemic diseases [1,2]. Fungal diseases associated with non-Candida albicans Candida (NCAC) species have been globally increasing [3,4]. C. glabrata are about 15% of all Candida species-related systemic bloodstream infections [5,6], which is relevant since, compared with other Candida species infections, the mortality rate associated with C. glabrata is the highest (30%) [1,7]. As a matter of fact, the biofilm formation is a very important virulence factor for C. glabrata, allowing the yeasts to adhere to biotic and abiotic surfaces, developing into organized communities that are extremely refractory to antifungal treatment and environmental conditions [8]. The cell wall is comprised of an internal central core of β-1,3 glucans and β-1,6 glucans linked to chitin via β-1,4 glucans, extended
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