Rifampicin induces MDR1 expression in Candida albicans.
OBJECTIVE
Overexpression of efflux pumps such as MDR1 has been identified as an important mechanism contributing to fluconazole resistance in Candida albicans. This phenomenon is frequently observed in fluconazole-resistant strains isolated from AIDS patients treated with various pharmaceuticals. Therefore, we hypothesized that some of these compounds might influence the expression of genes responsible for fluconazole resistance.


METHODS
We examined a variety of clinically relevant compounds for their in vitro effects on MDR1 expression with a C. albicans reporter strain containing a transcriptional fusion of the MDR1 promoter (MDR1P) with the gfp gene. Activation of the MDR1 promoter and subsequent green fluorescent protein production was determined by fluorescence microscopy and flow cytometry. Additionally, MDR1 transcription was confirmed and quantified by RT-PCR analysis, followed by Mdr1p detection by western blot. Finally, the effect of a selected agent on resistance to fluconazole was tested by chequerboard titration of both substances.


RESULTS
Of 15 compounds tested, only rifampicin induced a rapid and dose-dependent increase in MDR1 expression (up to 122-fold induction), whereas structurally related molecules such as rifabutin and rifamycin were not active. Induction of MDR1 expression upon rifampicin exposure was also observed in 10 blood culture isolates. In contrast, rifampicin exposure did not markedly affect the expression of the transporters CDR1 and CDR2. Increased MDR1 expression was accompanied by elevated MICs for fluconazole after exposure of C. albicans to rifampicin, whereas Mdr1p expression was only moderately induced.


CONCLUSIONS
Out of the compounds examined, only rifampicin specifically induced MDR1 expression in all C. albicans strains tested. Rifampicin may play a general role in signal transduction or another means of modulation of gene expression in C. albicans.
Vogel
Miriam
M
Institut für Medizinische Mikrobiologie und Hygiene, Eberhard-Karls-Universität, 72076 Tübingen, Germany.
Hartmann
Timo
T
Köberle
Martin
M
Treiber
Monika
M
Autenrieth
Ingo B
IB
Schumacher
Ulrike K
UK
D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis* / Q000235:genetics; D002176:Candida albicans / Q000187:drug effects / Q000502:physiology*; D025141:Drug Resistance, Fungal / Q000187:drug effects / Q000502:physiology; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D012293:Rifampin / Q000494:pharmacology*
C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D012293:Rifampin