Open AccessIdentification and Expression of Multidrug Transporters Responsible for Fluconazole Resistance in Candida dubliniensis
Author(s) -
Gary P. Moran,
Dominique Sanglard,
Samantha M. Donnelly,
Diarmuid B. Shanley,
Derek J. Sullivan,
David C. Coleman
Publication year - 1998
Publication title -
antimicrobial agents and chemotherapy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.07
H-Index - 259
eISSN - 1070-6283
pISSN - 0066-4804
DOI - 10.1128/aac.42.7.1819
Subject(s) - fluconazole , multiple drug resistance , candida dubliniensis , identification (biology) , microbiology and biotechnology , atp binding cassette transporter , biology , drug resistance , transporter , genetics , antifungal , gene , corpus albicans , botany
Candida dubliniensis is a recently describedCandida species associated with oral candidosis in human immunodeficiency virus (HIV)-infected and AIDS patients, from whom fluconazole-resistant clinical isolates have been previously recovered. Furthermore, derivatives exhibiting a stable fluconazole-resistant phenotype have been readily generated in vitro from fluconazole-susceptible isolates following exposure to the drug. In this study, fluconazole-resistant isolates accumulated up to 80% less [3 H]fluconazole than susceptible isolates and also exhibited reduced susceptibility to the metabolic inhibitors 4-nitroquinoline-N -oxide and methotrexate. These findings suggested thatC. dubliniensis may encode multidrug transporters similar to those encoded by theC. albicans MDR1 ,CDR1 , andCDR2 genes (CaMDR1 ,CaCDR1 , andCaCDR2 , respectively). AC. dubliniensis homolog ofCaMDR1 , termedCdMDR1 , was cloned; its nucleotide sequence was found to be 92% identical to the correspondingCaMDR1 sequence, while the predicted CdMDR1 protein was found to be 96% identical to the corresponding CaMDR1 protein. By PCR,C. dubliniensis was also found to encode homologs ofCDR1 andCDR2 , termedCdCDR1 andCdCDR2 , respectively. Expression ofCdMDR1 in a fluconazole-susceptible Δpdr5 null mutant ofSaccharomyces cerevisiae conferred a fluconazole-resistant phenotype and resulted in a 75% decrease in accumulation of [3 H]fluconazole. Northern analysis of fluconazole-susceptible and -resistant isolates ofC. dubliniensis revealed that fluconazole resistance was associated with increased expression ofCdMDR1 mRNA. In contrast, most studies showed that overexpression ofCaCDR1 was associated with fluconazole resistance inC. albicans . Increased levels of the CdMdr1p protein were also detected in fluconazole-resistant isolates. Similar results were obtained with fluconazole-resistant derivatives ofC. dubliniensis generated in vitro, some of which also exhibited increased levels ofCdCDR1 mRNA and CdCdr1p protein. These results demonstrate thatC. dubliniensis encodes multidrug transporters which mediate fluconazole resistance in clinical isolates and which can be rapidly mobilized, at least in vitro, on exposure to fluconazole.