Candida albicans is one of microorganisms of physiological human flora. It is normally isolated from mucous membrane of gastrointestinal and respiratory tracks, mouth and skin. Unfortunately this species is prone to cause opportunistic infections that consists mainly of superficial, though often persistent, oral or vaginal candidiasis. Much more problematic, and dangerous are systemic infections, called candidemias. These are most commonly seen in patients with severe immunosuppression that is caused by diseases which decrease the function of the immune system, such as cancer or AIDS or by prolonged exposure to antibio- or chemotherapy. Unfortunately, in recent years an increase in resistance of C. albicans to known antifungal agents has been observed. Additionally some of isolates display resistance to more than one drug, so called multidrug resistance MDR, which basically renders our attempts to treat this kind of infection futile.

C. albicans can develop many different kinds of mechanisms of drug resistance, such as forming biofilms, changing composition of cell membrane or structure of drug transforming enzymes. Overexpression of MDR transporters, which actively export xenobiotics from cell, is only another example. In C. albicans three of these pumps were identified: CDR1, CDR2 (Candida drug resistance 1 and 2), which belong to ABC (ATP-biding cassettes) transporters family, that use energy from ATP hydrolysis and MDR1 from MFS family (Major Facilitator Superfamily), which use energy from proton transport across membrane.

In our laboratory we are investigating effects of various chemical compounds on activity of ABC transporters of C. albicans. Main method used in this study is real-time monitoring technique based on uptake of fluorescent dye, 3,3′-dipropylthiacarbocyanine iodide (diS-C₃(3)), into the cell. Probe binding with cell components results in the change of its fluorescence parameters which shows as shift of λ_max in direction of longer waves (so called “red shift”). In turn, increase of cell membrane permeability caused for example by overexpression or increased activity of MDR pumps results in dye release from the cell which shows as shift of λ_max in shorter waves direction (“blue shift”). Using this method we hope to find potential effective inhibitors for ABC transporters which can be used as antifungal agents in future.