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The effect of subinhibitory concentrations of antifungal agents on variation of cell surface hydrophobicity and biofilm formation with relation to genotype of Candida albicans and Candida dubliniensis

Abstract number: 1134_04_76

Melkusová S., Bujdáková H., Volleková A., Lisalová M.

Objectives:  

This work studied the variation of cell surface hydrophobicity (CSH), the biofilm formation and their relationship to genotype in clinical isolates of C. albicans and C. dubliniensis. Next objective was aimed at the effect of sub inhibitory concentrations of the conventional azole derivates fluconazole and itraconazole, the new azole voriconazole, polyene amphotericin B and the experimental antifungal agent 6-amino-2-n-pentylthiobenzothiazole (APB) on both CSH and biofilm formation.

Methods:  

For this study, 50 C. albicans and C. dubliniensis clinical isolates from immunocompromised patients were collected. Genotyping of Candida isolates was performed by PCR assay using set primer pair: Ca-INT-L and Ca-INT-R. The CSH was measured by biphasic separation method in YNB medium/octane overlay. Biofilm formation was quantified as the ability to adhere to polystyrene plastic surfaces and the formation of biofilm was measured by the XTT reduction assay. The MIC95 values for tested antifungal agents were established by broth microdilution method according to NCCLS M27-A reference method and these values were used to calculate sub inhibitory concentrations in subsequent experiments.

Results:  

All C. albicans isolates were separated into three genotype groups: genotype A (12), genotype B (13), genotype C (12). Thirteen isolates represented genotype D (C. dubliniensis). In the XTT assay, the mean A490 values for the 50 strains were 0.359 ± 0.130, for the genotype A 0.42 ± 0.154, for the genotype B 0.262 ± 0.072, for the genotype C 0.281167± 0.059 and for genotype D 0,.471231 ± 0.07. The relative hydrophobicity of cells was established: 11.48% for the genotype A, 18.32% for the genotype B, 18.44% for the genotype C and 71.55% for genotype D. Although, no significant difference was detected among biofilm formation in genotype A and genotype D, the CSH calculated for genotype D was 6.2-fold highest in comparison with genotype A. The difference between genotype B and C was determined neither in biofilm formation nor in CSH. The influence of sub inhibitory concentrations of tested antifungal agents on CSH and biofilm formation was observed as well. Moreover, sub inhibitory concentration of fluconazole decreased the ability to form biofilm, but increased the CSH in fluconazole-resistant isolates.

Conclusion:  

Results suggested the association between genotype and biofilm formation, as well as confirmed the effect of antifungal agents on both biofilm and CSH.

Session Details

Date: 01/08/2007
Time: 00:00-00:00
Session name: XXIst ISTH Congress
Subject:
Location: Oxford, UK
Presentation type:
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