AAC
Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Sanguinetti, M.
Right arrow Articles by Fadda, G.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Sanguinetti, M.
Right arrow Articles by Fadda, G.

 Previous Article  |  Next Article 

Antimicrobial Agents and Chemotherapy, February 2005, p. 668-679, Vol. 49, No. 2
0066-4804/05/$08.00+0     doi:10.1128/AAC.49.2.668-679.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Mechanisms of Azole Resistance in Clinical Isolates of Candida glabrata Collected during a Hospital Survey of Antifungal Resistance

Maurizio Sanguinetti,* Brunella Posteraro, Barbara Fiori, Stefania Ranno, Riccardo Torelli, and Giovanni Fadda

Istituto di Microbiologia, Università Cattolica del Sacro Cuore, Rome, Italy

Received 9 July 2004/ Returned for modification 11 August 2004/ Accepted 15 October 2004

The increasing use of azole antifungals for the treatment of mucosal and systemic Candida glabrata infections has resulted in the selection and/or emergence of resistant strains. The main mechanisms of azole resistance include alterations in the C. glabrata ERG11 gene (CgERG11), which encodes the azole target enzyme, and upregulation of the CgCDR1 and CgCDR2 genes, which encode efflux pumps. In the present study, we evaluated these molecular mechanisms in 29 unmatched clinical isolates of C. glabrata, of which 20 isolates were resistant and 9 were susceptible dose dependent (S-DD) to fluconazole. These isolates were recovered from separate patients during a 3-year hospital survey for antifungal resistance. Four of the 20 fluconazole-resistant isolates were analyzed together with matched susceptible isolates previously taken from the same patients. Twenty other azole-susceptible clinical C. glabrata isolates were included as controls. MIC data for all the fluconazole-resistant isolates revealed extensive cross-resistance to the other azoles tested, i.e., itraconazole, ketoconazole, and voriconazole. Quantitative real-time PCR analyses showed that CgCDR1 and CgCDR2, alone or in combination, were upregulated at high levels in all but two fluconazole-resistant isolates and, to a lesser extent, in the fluconazole-S-DD isolates. In addition, slight increases in the relative level of expression of CgSNQ2 (which encodes an ATP-binding cassette [ABC] transporter and which has not yet been shown to be associated with azole resistance) were seen in some of the 29 isolates studied. Interestingly, the two fluconazole-resistant isolates expressing normal levels of CgCDR1 and CgCDR2 exhibited increased levels of expression of CgSNQ2. Conversely, sequencing of CgERG11 and analysis of its expression showed no mutation or upregulation in any C. glabrata isolate, suggesting that CgERG11 is not involved in azole resistance. When the isolates were grown in the presence of fluconazole, the profiles of expression of all genes, including CgERG11, were not changed or were only minimally changed in the resistant isolates, whereas marked increases in the levels of gene expression, particularly for CgCDR1 and CgCDR2, were observed in either the fluconazole-susceptible or the fluconazole-S-DD isolates. Finally, known ABC transporter inhibitors, such as FK506, were able to reverse the azole resistance of all the isolates. Together, these results provide evidence that the upregulation of the CgCDR1-, CgCDR2-, and CgSNQ2-encoded efflux pumps might explain the azole resistance in our set of isolates.

* Corresponding author. Mailing address: Istituto di Microbiologia, Largo F. Vito, 1-00168 Rome, Italy. Phone: 39 6 30154964. Fax: 39 6 3051152. E-mail: msanguinetti{at}rm.unicatt.it.

Antimicrobial Agents and Chemotherapy, February 2005, p. 668-679, Vol. 49, No. 2
0066-4804/05/$08.00+0     doi:10.1128/AAC.49.2.668-679.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:



Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
Clin. Vaccine Immunol. Clin. Microbiol. Rev.
J. Clin. Microbiol. ALL ASM JOURNALS

Copyright © 2005 by the American Society for Microbiology. All rights reserved.