DUBLIN, Ireland - The leader of a research group at Trinity College Dublin that first described a new species of Candida received the Royal Irish Academy prize for excellence in microbiological research last week. The species, dubbed Candida dubliniensis, has emerged as a significant opportunistic pathogen in AIDS patients worldwide.

The yeast initially was confused with Candida albicans, long-recognized as a source of opportunistic infections in immunocompromised individuals. “Phenotypically, it's very similar, said David Coleman, professor of microbiology in the school of dental science at the college, who headed up the research team.

C. dubliniensis produces germ tubes, which resemble miniature hyphae, and asexual chlamydospores, two traits that were used as diagnostic tests for C. albicans until 1995, when the new species was first described. The two species differ greatly at the genomic level, though. C. dubliniensis has 13 pairs of chromosomes, which often fragment, whereas C. albicans has 10. The rRNA sequences of the two species also diverge.

C. dubliniensis - which, like C. albicans, is part of the body's normal microbial population - has posed a problem in AIDS treatment because it develops resistance to antifungal drugs “literally overnight,“ said Coleman. His group has cloned and sequenced a chromosomal gene encoding an ATP transporter protein, called Candida dubliniensis MDR1, which has six transmembrane domains and a hydrophilic tail. This acts as a drug pump. His group currently is attempting to work out the details of its genetic regulation.

Coleman's group has also isolated two other unrelated drug resistance genes in C. dubliniensis. Both belong to the multifacilitator group of transport proteins, which is common across the eukaryotic kingdom. - Cormac Sheridan

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