The effect of nystatin on Candida spp. yeasts in different environments

Abstract

Candida albicans and Candida glabrata are among the most important opportunistic pathogens that cause thousands of superficial or disseminated and fatal infections in immunocompromised individuals every year. These yeasts can acquire resistance to all four known classes of antifungal drugs, making the treatment of these infections much harder [1]. It is necessary to find new antifungal compounds or ways to strengthen the effect of those already known. Polyene drug nystatin creates pores in the cell wall, increasing the plasma membrane permeability and osmotic disbalance [2]. This study aimed to evaluate the effect of this antifungal drug on C. albicans and C. glabrata yeasts in different environments – buffer solutions and growth media of different pH. It was determined that the deletion of efflux pump genes of ABC superfamily CDR1 and/or CDR2 did not have an impact on the cells’ sensitivity to this drug which means that one of the popular ways to strengthen the effects of antifungal drugs by inhibiting the efflux pumps would not improve the efficiency of nystatin. Since the inhibition of efflux pumps is not a suitable way to strengthen the effect of this antifungal, the impact of different environments was tested. Effects of nystatin on Candida yeasts can be followed using real-time methods such as the analysis of lipophilic anion PCB- binding to yeast cells. After evaluation of the effects of nystatin at different pHs of citrate-phosphate buffer, it was determined that C. albicans and C. glabrata wild-type cells bound the highest amount of PCB- ions when the buffer pH was 3. Some differences between the tested yeasts were noted. At pH 6 and pH 8, C. glabrata cells, exposed to nystatin, bound less PCB- than C. albicans cells, but at pH 3 C. glabrata cells bound more PCB- compared to C. albicans ones. Moreover, the effect of nystatin on the yeast of both species was also stronger in growth media of pH 3 compared to pH 6. These findings suggest that the efficiency of nystatin can be strengthened in an acidic environment, but further research on this problem is still needed