Prevalence of molecular mechanisms of resistance to azole antifungal agents in Candida albicans strains displaying high-level fluconazole resistance isolated from human immunodeficiency virus-infected patients.
Molecular mechanisms of azole resistance in Candida albicans, including alterations in the target enzyme and increased efflux of drug, have been described, but the epidemiology of the resistance mechanisms has not been established. We have investigated the molecular mechanisms of resistance to azoles in C. albicans strains displaying high-level fluconazole resistance (MICs, > or =64 microg/ml) isolated from human immunodeficiency virus (HIV)-infected patients with oropharyngeal candidiasis. The levels of expression of genes encoding lanosterol 14alpha-demethylase (ERG11) and efflux transporters (MDR1 and CDR) implicated in azole resistance were monitored in matched sets of susceptible and resistant isolates. In addition, ERG11 genes were amplified by PCR, and their nucleotide sequences were determined in order to detect point mutations with a possible effect in the affinity for azoles. The analysis confirmed the multifactorial nature of azole resistance and the prevalence of these mechanisms of resistance in C. albicans clinical isolates exhibiting frank fluconazole resistance, with a predominance of overexpression of genes encoding efflux pumps, detected in 85% of all resistant isolates, being found. Alterations in the target enzyme, including functional amino acid substitutions and overexpression of the gene that encodes the enzyme, were detected in 65 and 35% of the isolates, respectively. Overall, multiple mechanisms of resistance were combined in 75% of the isolates displaying high-level fluconazole resistance. These results may help in the development of new strategies to overcome the problem of resistance as well as new treatments for this condition.
Perea
S
S
Department of Medicine, Division of Infectious Diseases, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78245, USA.
López-Ribot
J L
JL
Kirkpatrick
W R
WR
McAtee
R K
RK
Santillán
R A
RA
Martínez
M
M
Calabrese
D
D
Sanglard
D
D
Patterson
T F
TF
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D000935:Antifungal Agents / Q000494:pharmacology*; D001393:Azoles / Q000494:pharmacology*; D002176:Candida albicans / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D004352:Drug Resistance, Microbial / Q000235:genetics; D015725:Fluconazole / Q000494:pharmacology; D005787:Gene Frequency; D015658:HIV Infections / Q000382:microbiology*; D006801:Humans; D008826:Microbial Sensitivity Tests; D009154:Mutation; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D000075142:RUNX1 Translocation Partner 1 Protein; D058886:Sterol 14-Demethylase; D014157:Transcription Factors / Q000378:metabolism
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000935:Antifungal Agents; D001393:Azoles; C548418:CYP51A1 protein, human; D004268:DNA-Binding Proteins; D011518:Proto-Oncogene Proteins; D000075142:RUNX1 Translocation Partner 1 Protein; C082222:RUNX1T1 protein, human; D014157:Transcription Factors; D015725:Fluconazole; D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; D058886:Sterol 14-Demethylase