Differential Expression of the Genes Encoding Erg11 and Multidrug Efflux Transporters in Fluconazole Resistant Isolates of Non-albicans Species of Candida

Ref ID: 18802

Author:

E. L. Berkow, MS – Graduate Student, K. S. Barker, PhD – Assistant Professor, K. M. Brown, BS – Graduate Student, P. D. Rogers, PharmD, PhD – Professor;

Author address:

Univ. of Tennessee Hlth. Sci. Ctr., Memphis, TN.

Full conference title:

52nd Annual ICAAC

Date: 9 September 2014

Abstract:

Background: In Candida species, azole resistance involves multiple mechanisms including overexpression of genes encoding the azole target, lanosterol demethylase (ERG11) and those encoding multidrug efflux transporters. While much is known about these mechanisms in C. albicans and C. glabrata, their role in azole resistance in non-albicans species is less well understood. The purpose of this study was to determine which azole resistance genes are differentially expressed among resistant clinical isolates of C. krusei, C. tropicalis, and C. parapsilosis. Methods: We selected eight clinical isolates of each Candida species. For C. tropicalis and C. parapsilosis this included 1 fluconazole (FCZ) susceptible isolate and 7 with elevated FCZ minimum inhibitory concentrations (MICs). For C. krusei, all isolates exhibited elevated FCZ MICs. MICs were determined by CLSI methods. Relative expression of genes known to contribute to azole resistance was measured by RT-PCR. Genes interrogated were ERG11, ABC1, and ABC2 for C. krusei, and ERG11, MDR1, and CDR1 for C. tropicalis and C. parapsilosis. All experiments included biological and technical replicates in triplicate. Results: MICs of FCZ ranged from 16 to 256 μg/mL for C. krusei, <0.5 to >256 μg/mL for C. tropicalis, and <0.5 to 128 μg/mL for C. parapsilosis. Among C. krusei, 5 exhibited high levels of ABC1 and 4 exhibited high levels of ABC2. Among C. tropicalis, 5 overexpressed MDR1 and 5 overexpressed CDR1 relative to the susceptible control isolate. Among C. parapsilosis, 4 overexpressed CDR1 and 1 overexpressed MDR1. These genes were not consistently coordinately regulated within these species. No increases in ERG11 expression were observed for any isolates. Conclusions: These data suggest that high level azole resistance in C. krusei, C. tropicalis, and C. parapsilosis is multifactorial and involve multidrug efflux transporters. Further assessment of a role for overexpression of ERG11 in a larger number of isolates is needed. This study provides a foundation for future work towards the elucidation of the molecular basis of azole antifungal resistance in these species.

Abstract Number: M-969

Conference Year: 2012

Link to conference website: NULL

New link: NULL

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