R.D. Cannon, A.R. Holmes

ATP-binding cassette (ABC) proteins are ubiquitous in prokaryotes and eukaryotes. They are involved in energy-dependent transport of molecules across membranes. ABC proteins are often promiscuous transporters that can translocate a variety of substrates. In oral fungi, especially in Candida species, they have been implicated as major contributors to the high-level azole resistance of clinical isolates from infections that do not respond to drug therapy. While this is predominantly due to efflux of azoles from the cells, ABC proteins can contribute to fungal drug resistance in other ways as well. Cells in biofilms are notoriously resistant to antifungal agents. ABC proteins can contribute to this resistance through the efflux of drugs. Biofilms are complex communities of myriad microorganisms and, in order to survive in such a milieu, they need to communicate with, and respond to, microorganisms and their products. ABC proteins are involved in the secretion of fungal mating factors and quorum sensing molecules. These molecules affect biofilm structure and behaviour that can result in increased drug resistance. Thus, ABC proteins make multiple contributions to oral fungal drug resistance through a variety of responses to environmental signals. This article is protected by copyright. All rights reserved.