Genome-wide expression profiling reveals genes associated with amphotericin B and fluconazole resistance in experimentally induced antifungal resistant isolates of Candida albicans.
OBJECTIVE
The aim of this study was to identify changes in the gene expression profile of Candida albicans associated with the acquisition of experimentally induced resistance to amphotericin B and fluconazole.


METHODS
C. albicans SC5314 was passed in increasing concentrations of amphotericin B to generate isolate SC5314-AR. Susceptibility testing by Etest revealed SC5314-AR to be highly resistant to both amphotericin B and fluconazole. The gene expression profile of SC5314-AR was compared with that of SC5314 using DNA microarray analysis. Sterol composition was determined for both strains.


RESULTS
Upon examination of MICs of antifungal compounds, it was found that SC5314-AR was resistant to both amphotericin B and fluconazole. By microarray analysis a total of 134 genes were found to be differentially expressed, that is up-regulated or down-regulated by at least 50%, in SC5314-AR. In addition to the cell stress genes DDR48 and RTA2, the ergosterol biosynthesis genes ERG5, ERG6 and ERG25 were up-regulated. Several histone genes, protein synthesis genes and energy generation genes were down-regulated. Sterol analysis revealed the prevalence of sterol intermediates eburicol and lanosterol in SC5314-AR, whereas ergosterol was the predominant sterol in SC5314.


CONCLUSIONS
Along with changes in expression of these ergosterol biosynthesis genes was the accumulation of sterol intermediates in the resistant strain, which would account for the decreased affinity of amphotericin B for membrane sterols and a decreased requirement for lanosterol demethylase activity in membrane sterol production. Furthermore, other genes are implicated as having a potential role in the polyene and azole antifungal resistant phenotype.
Barker
Katherine S
KS
Department of Pharmacy, College of Pharmacy, University of Tennessee Health Science Center, Memphis, USA.
Crisp
Sarah
S
Wiederhold
Nathan
N
Lewis
Russell E
RE
Bareither
Bart
B
Eckstein
James
J
Barbuch
Robert
R
Bard
Martin
M
Rogers
P David
PD
D000666:Amphotericin B / Q000494:pharmacology*; D000935:Antifungal Agents / Q000494:pharmacology*; D002176:Candida albicans / Q000187:drug effects* / Q000235:genetics*; D002177:Candidiasis / Q000382:microbiology*; D003577:Cytochrome P-450 Enzyme System / Q000494:pharmacology; D017931:DNA Primers; D018076:DNA, Complementary / Q000096:biosynthesis / Q000235:genetics; D025141:Drug Resistance, Fungal; D004875:Ergosterol / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology; D015725:Fluconazole / Q000494:pharmacology*; D020869:Gene Expression Profiling; D005800:Genes, Fungal / Q000235:genetics*; D016681:Genome, Fungal; D006801:Humans; D008826:Microbial Sensitivity Tests; D020411:Oligonucleotide Array Sequence Analysis; D010088:Oxidoreductases / Q000494:pharmacology; D010641:Phenotype; D017510:Protein Folding; D012331:RNA, Fungal / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics; D058886:Sterol 14-Demethylase; D013261:Sterols / Q000378:metabolism
D000935:Antifungal Agents; C548418:CYP51A1 protein, human; D017931:DNA Primers; D018076:DNA, Complementary; D012331:RNA, Fungal; D013261:Sterols; D000666:Amphotericin B; D015725:Fluconazole; D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; D058886:Sterol 14-Demethylase; D004875:Ergosterol