Exposure of Candida albicans to antifungal agents affects expression of SAP2 and SAP9 secreted proteinase genes

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Abstract
Objectives: To ascertain the effects of subinhibitory concentrations of several antifungal agents on a virulence factor: secreted proteinase (Sap) activity and expression of SAP genes in Candida albicans. Methods: Enzyme assays and growth measurements, GFP-SAP2 promoter constructs and fluorescence measurement, transcript profiling and RT–PCR. Results: For seven of eight C. albicans isolates tested, exposure to fluconazole gave an increase in Sap specific activity; for one isolate, resistant to azoles and flucytosine, fluconazole exposure led to a fall in Sap activity. A similar relationship between growth reduction and increased Sap activity was seen with C. albicans cells treated with subinhibitory concentrations of itraconazole, miconazole, flucytosine and caspofungin. Transcript profiling indicated antifungal exposure was associated with increased expression of mRNA from SAP2 and SAP9 genes; this was confirmed for fluconazole and caspofungin exposure by RT–PCR. Conclusions: Antifungal agents with three different mechanisms of action similarly generate a rise in expression of SAP2 and activity of the secreted Sap2 gene product, a known virulence factor, in most isolates of C. albicans. One isolate of the fungus showed an opposite response.

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