Enhancement of yeast susceptibility to antifungals

Abstract number: 1733_1460

Subik J., Cernicka J., Kozovska Z., Valachovic M., Hapala I., Hajos G.

Objectives: Decreased susceptibilities to azole antifungals in Candida species were resulting from combination of several molecular mechanisms involving the enhanced expression of drug transporter genes (MDR1, CDR1/2) and over-expression or mutations in the ERG11 gene encoding the 14-a-lanosterol demethylase. To overcome multidrug resistance in yeast pathogens, antifungals with novel cellular targets as well as multidrug resistance reversal agents rendering drug resistant strains sensitive to commercially used antifungals are being developed. In this report one polyfused heterocyclic compound was found to enhance the activity of several antifungals in different yeast species.

Methods: A library of polyfused heterocyclic compounds was tested for multidrug resistance modulating activity in a screening system using the agar diffusion method. Drug susceptibilities were assayed by microbroth dilution method in 96-well plates according to the proposed NCCLS M27-A standard guidelines. RP-HPLC analysis of sterols was conducted on Eclipse XDB-C8 column using an Agilent 1100 series instrument. Accumulation of rhodamine 6G (Sigma) was measured by flow cytometry in a FACS Calibur fluorescence-activated cell cytometer (Becton Dickinson).

Results: We identified one compound able to enhance the susceptibility to cycloheximide and other drugs in the drug resistant Saccharomyces cerevisiae mutant strain. In the presence of this organic compound an increased antifungal activity of fluconazole was demonstrated in yeast mutant strains deleted in genes encoding the major multidrug resistance transcription factors Yap1p, Pdr1p and Pdr3p, as well as the drug efflux pumps Pdr5p and Snq2p in S. cerevisiae or their counterparts in C. albicans and C. glabrata, named Cdr1p and Mdr1p, respectively. Importantly, the compound increased the sensitivity to fluconazole also in multidrug resistant cells over-expressing the efflux pumps. Yeast cells grown in the presence of sub-inhibitory concentrations of the compound exhibited an altered sterol composition and a slightly enhanced accumulation of rhodamine 6G, which suggests that plasma membrane plays a role in yeast sensitisation to drugs.

Conclusion: The activity of a new compound that can overcome multidrug resistance in yeast may prove useful in combined treatment of infections caused by drug resistant fungal pathogens.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
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