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Antimicrobial Agents and Chemotherapy, September 2008, p. 3259-3266, Vol. 52, No. 9
0066-4804/08/$08.00+0     doi:10.1128/AAC.00541-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Cell Density and Cell Aging as Factors Modulating Antifungal Resistance of Candida albicans Biofilms {triangledown}

C. J. Seneviratne,* L. J. Jin, Y. H. Samaranayake, and L. P. Samaranayake

Oral Biosciences, Faculty of Dentistry, The University of Hong Kong, Hong Kong

Received 28 April 2008/ Returned for modification 17 May 2008/ Accepted 6 July 2008

Biofilm formation is a major virulence attribute of Candida pathogenicity which contributes to higher antifungal resistance. We investigated the roles of cell density and cellular aging on the relative antifungal susceptibility of planktonic, biofilm, and biofilm-derived planktonic modes of Candida. A reference and a wild-type strain of Candida albicans were used to evaluate the MICs of caspofungin (CAS), amphotericin B (AMB), nystatin (NYT), ketoconazole (KTC), and flucytosine (5FC). Standard, NCCLS, and European Committee on Antibiotic Susceptibility Testing methods were used for planktonic MIC determination. Candida biofilms were then developed on polystyrene wells, and MICs were determined with a standard 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium hydroxide assay. Subsequently, antifungal susceptibility testing was performed for greater inoculum concentrations and 24- and 48-h-old cultures of planktonic Candida. Furthermore, Candida biofilm-derived planktonic cells (BDPC) were also subjected to antifungal susceptibility testing. The MICs for both C. albicans strains in the planktonic mode were low, although on increasing the inoculum concentration (up to 1 x 108 cells/ml), a variable MIC was noted. On the contrary, for Candida biofilms, the MICs of antifungals were 15- to >1,000-fold higher. Interestingly, the MICs for BDPC were lower and were similar to those for planktonic-mode cells, particularly those of CAS and AMB. Our data indicate that higher antifungal resistance of Candida biofilms is an intrinsic feature possibly related to the biofilm architecture rather than cellular density or cellular aging.

* Corresponding author. Mailing address: Oral Biosciences, Faculty of Dentistry, The University of Hong Kong, Prince Philip Dental Hospital, 34 Hospital Road, Hong Kong. Phone: (852) 28590480. Fax: (852) 25476133. E-mail: lakshman{at}hku.hk

{triangledown} Published ahead of print on 14 July 2008.

Antimicrobial Agents and Chemotherapy, September 2008, p. 3259-3266, Vol. 52, No. 9
0066-4804/08/$08.00+0     doi:10.1128/AAC.00541-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Ferreira, J. A. G., Carr, J. H., Starling, C. E. F., de Resende, M. A., Donlan, R. M. (2009). Biofilm Formation and Effect of Caspofungin on Biofilm Structure of Candida Species Bloodstream Isolates. Antimicrob. Agents Chemother. 53: 4377-4384 [Abstract] [Full Text]  


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