Candida albicans and Candida glabrata yeast are successful commensals and opportunistic pathogens of humans that cause superficial or disseminated infections in immunocompromised and hospitalized individuals. These yeasts are only sensitive to four classes of antifungals, but the cells can acquire multidrug resistance [1]. Therefore, it is necessary to find ways to strengthen the efficiency of already-known drugs to fight against Candida infections.
This study aimed to evaluate the efficiency of nystatin – antifungal polyene drug which creates pores in the cell envelope, increasing the plasma membrane permeability and osmotic disbalance [2] - on C. albicans and C. glabrata cells in salt buffers and growth media of various acidity. The effects of nystatin on Candida yeast were followed using real-time methods, such as registering lipophilic anion binding to the cells, the cell respiration rate, and the cells’ ability to keep a \(K^{+}\) gradient. These methods allowed us to monitor different antifungals’ effects in tenths of minutes. This was much faster compared to the traditional assays using agar or immunological plates, which usually require incubation for more than 18 hours. After evaluating the effects of nystatin on the cell suspensions in the growth media - RPMI and YPD - or citrate-phosphate buffer of different pH, it was observed that both C. albicans and C. glabrata cells bind the highest amount of \(PCB^{-}\) at acidic conditions. A quicker and stronger inhibition of the respiration of C. albicans and C. glabrata cells by nystatin was also observed when the incubation medium pH was as low as 3. Our findings suggest that the antifungal drug nystatin could be more effective in an acidic environment, but further research is still needed.