Comparison of Biofilms Formed byCandidaalbicansandCandidaparapsilosison Bioprosthetic Surfaces

Abstract

Little is known about fungal biofilms, which may cause infection and antibiotic resistance. In this study, biofilm formation by different Candida species, particularly Candida albicans and C. parapsilosis, was evaluated by using a clinically relevant model of Candida biofilm on medical devices. Candida biofilms were allowed to form on silicone elastomer and were quantified by tetrazolium (XTT) and dry weight (DW) assays. Formed biofilm was visualized by using fluorescence microscopy and confocal scanning laser microscopy with Calcofluor White (Sigma Chemical Co., St. Louis, Mo.), concanavalin A-Alexafluor 488 (Molecular Probes, Eugene, Oreg.), and FUN-1 (Molecular Probes) dyes. Although minimal variations in biofilm production among invasive C. albicans isolates were seen, significant differences between invasive and noninvasive isolates (P < 0.001) were noted. C. albicans isolates produced more biofilm than C. parapsilosis, C. glabrata, and C. tropicalis isolates, as determined by DW assays (P was <0.001 for all comparisons) and microscopy. Interestingly, noninvasive isolates demonstrated a higher level of XTT activity than invasive isolates. On microscopy, C. albicans biofilms had a morphology different from that of other species, consisting of a basal blastospore layer with a dense overlying matrix composed of exopolysaccharides and hyphae. In contrast, C. parapsilosis biofilms had less volume than C. albicans biofilms and were comprised exclusively of clumped blastospores. Unlike planktonically grown cells, Candida biofilms rapidly (within 6 h) developed fluconazole resistance (MIC, >128 g/ml). Importantly, XTT and FUN-1 activity showed biofilm cells to be metabolically active. In conclusion, our data show that C. albicans produces quantitatively larger and qualitatively more complex biofilms than other species, in particular, C. parapsilosis.

Efficacy of 7‐benzyloxyindole and other halogenated indoles to inhibit Candida albicans biofilm and hyphal formation

“…Colorimetric assays are valuable for quantifying the viabilities of eukaryotic cells, and it has been suggested the XTT assay is useful to study fungal biofilm formation and drug resistance (Chandra et al ., 2001; Kuhn et al ., 2002). Findings from our XTT assay showed that metabolic activity of biofilm and planktonic C. albicans cells was not affected after 7‐benzyloxyindole treatment at 0.02 and 0.05 mM (Fig.…”

“…Altman (1976) reported mitochondrial succinoxidase, cytochrome P450 and flavoprotein oxidases are primarily responsible for the conversion of XTT to coloured formazan, which is important in fungal research because XTT conversion provides a measure of metabolic activity, which is related to fungal wall biosynthesis. (Kuhn et al ., 2002). This findings imply that 7‐benzyloxyindole at concentrations of >0.1 mM reduced metabolic activity due to low levels of C. albicans cells in biofilms (Fig.…”

Transcription factor Efg1 contributes to the tolerance of Candida albicans biofilms against antifungal agents in vitro and in vivo

“…Moreover, Ramage et al (2002) found Defg1 sessile cells to be equally resistant to AmB compared to the WT. Such inter-study variations highlight the differences in susceptibilities of Candida biofilms, which can be strongly influenced by different setups, including the type of device, composition and pH of the medium (Kucharíková et al, 2011) and the quantification/susceptibility methods used (Kuhn et al, 2002b).…”

Catheter-related bloodstream infections: catheter management according to pathogen

“…differ in their capacity to form biofilms [23]. Mature Candida biofilms exhibit a complex three-dimensional structure and display extensive spatial heterogeneity [21,23,24]. The overall architecture of the biofilm may vary depending on the substrate on which it is formed and its growth conditions [25].…”

“…Different strains of C. albicans and different Candida spp. differ in their capacity to form biofilms [23]. Mature Candida biofilms exhibit a complex three-dimensional structure and display extensive spatial heterogeneity [21,23,24].…”