Comparative Effects on Candida albicans Cell Wall Chitin Content and Antifungal Activity of Triazoles and Amphotericin B

Ref ID: 19262

Author:

D. Daydé, B. Touquet, J. Delaroche, J. Forel, D. Aldebert, M. Cornet

Author address:

LAPM, UMR 5163 CNRS Université Joseph Fourier (UJF), Grenoble, FRANCE

Full conference title:

53rd Interscience Conference on Antimicrobial Agents and Chemotherapy

Date: 10 September 2014

Abstract:

Background: Effects of fluconazole (FCZ) on cell wall stucture have been described but not those of other triazoles and amphotericin B (AMB). The aim of this study was to compare the effects of the antifungal agents targeting the membrane on the cell wall structure and thickness. Methods: The yeasts were exposed to the triazoles (FCZ, voriconazole (VCZ) and posaconazole (PCZ)) and amphotericin B (AMB). They were labeled with calcofluor white (CFW, a chitin fluorescent dye). The growth inhibition and chitin content were analyzed by epifluorescence microscopy and a high content screening (HCS) method. Wall structure was determined by transmission electron microscopy (TEM) analysis and chemical chitin dosage based on acetylglucosamine level after acid hydrolysis. For TEM analysis, yeasts were embedded in epoxy resin and morphometric measurements were performed on ultrathin section (60 nm) using iTEM (Olympus) software. Results: Azole exposition led to a significant increase in the intensity of fluorescence which was used to measure the wall thickness. FCZ 0.5 μg/mL, VCZ 0.01μg/mL and PCZ 0.02μg/mL led to 75%, 87% and 76%, respectively, of the
yeasts showing significant thickened wall corresponding to
chitin accumulation. The rates of thickened cells were
correlated with the rates of growth inhibition that were
automatically calculated and confirmed by agar plates CFU
counting. TEM established significant expansion of the wall
layer with a mean thickness of 235 nm and 190 nm for the
cells exposed to FCZ and untreated cells, respectively
(p<0.001). Chitin dosage showed its accumulation upon FCZ exposure. Using AMB (up to 2.5 μg/mL), modification of the chitin content was detected neither with the CFW microscopy HCS method nor TEM or chitin dosage.Conclusions: Triazoles and AMB are both membrane-perturbing antifungal agents but affect differentially the cell wall structure. The marked chitin accumulation upon triazole exposure is not observed with AMB. These results suggest that the cell wall repair mechanisms leading to enhanced chitin synthesis are not activated by AMB. These observations may explain the fungicidal activity of AMB.

Abstract Number: NULL

Conference Year: 2013

Link to conference website: NULL

New link: NULL

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