Abstract
Biofilm formation by Candida species is a major contribute to their pathogenic potential.The aim of this study was to determine in vitro effects of EDTA, cycloheximide, and heparin-benzyl alcohol preservative on C. albicans (126) and non-albicans (31)vaginal yeast isolates biofilm formations and their susceptibility against three antifungal Etest strips. Results of the crystal violet-assay, indicated that biofilms formation were most commonly observed [100%] for C. kefyr, C. utilis, C. famata, and Rhodotorula mucilaginosa, followed by C. glabrata [70%], C. tropicalis [50%], C. albicans [29%], Saccharomyces cerevisiae [0.0%]. EDTA (0.3mg/ml) significantly inhibited biofilm formation in both C. albicans and non-albicans isolates (P=0.0001) presumably due to chelation of necessary metal cations for the process-completion. In contrast, heparin (-benzyl alcohol preservative) stimulated biofilm formation in all tested isolates, but not at significant level (P=0.567). Conversely, cycloheximide significantly (P=0.0001) inhibited biofilm formation in all C. albicans strains(126) and its effect was even 3 fold more pronounced than EDTA inhibition, probably due to its attenuation of proteins (enzymes) and/or complex molecules necessary for biofilm formation. Results also showed that all nonalbicans yeasts isolates were susceptible to 5-flucytosine (MIC50, 0.016 µg/ml; MIC90, 0.064 µg/ml), but 14% of C. albicans isolates were resistant (MIC50, 0.064 µg/ml; MIC90 >32 µg/ml). The MIC50 value of amphotricin B for all C. albicans and non-albicans isolates was at a narrow range of 0.023 µg /ml, and the MIC90 values were 0.047 µg/ml and 0.064 µg/ml respectively, thereby confirming its efficacy as a first line empiric- treatment of Candida spp infections.
Highlights
Species of Candida are considered important opportunistic pathogens
Results showed that all Candida spp. including C. albicans were susceptible to amphotericin B and to 5-flucytosine with the exception 14% of the C. albicans strains
The phenomenon of in vitro biofilm formation by microbes on various abiotic surfaces has been extensively studied in bacteria and to a lesser extent in fungi, and there appears to be a direct relationship between the capability of organisms to form a biofilm and their pathogenicity
Summary
Species of Candida are considered important opportunistic pathogens. Despite advances in antifungal therapy, the high attributable mortality rate (~40-60%), due to Candida infections has not clearly improved in the last 2 decades [3, 4]. Many of these infections are implant-associated infections, where the micro-organisms form adherent biofilms on the surfaces of catheters, joint replacements, prosthetic heart valves, and other medical devices [5]. Biofilm formation on biotic and abiotic surfaces is a key pathogenic attribute of Candida spp. that enhances its ability to adhere to surfaces and thereby maintain colonization and/or cause diseases in humans.
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