Two agents are licensed for the treatment of A. fumigates infection, amphotericin B and itraconazole. Resistance to itraconazole has been detected in vitro and has been validated in vivo. Studies of Saccharomyces cerevisiae and Candida species have shown that one mechanism of azole resistance is drug efflux by ATP-binding cassette (ABC) transporters. An A. fumigates genomic library was screened with a probe from the C. albicans ABC transporter gene, CDR]. This screening revealed a novel gene, ADRl, which has a high level of identity to other fungal mufti-drug resistance (MDR) genes. The encoded protein contains conserved amino acid residues within recognised MDR motifs. As well as hybridising to the gene, an ADRl probe hybridised to other sequences in the genome at high stringency. Dot blot analysis showed that ADRI mRNA is expressed at over 5-fold higher levels in a resistant isolate (AF72) which is unable to accumulate itraconazole. However, expression was only up-regulated when AF72 was grown in the presence of itraconazole. The regulation of this gene was also studied in response to heat shock, oxidative stress and other anti-fungal drugs, including terbinafine. Adrl is a novel ABC transporter, possibly involved in the efflux of itraconazole from A. fumigates. Complementation studies in yeast will be undertaken to establish the protein's substrate range.
Fungal Genet. Newsl. 46 (Supl):
Full conference title:
Fungal Genetics Conference 20th
- Fungal Genetics Conference 20th (1999)