The impact of growth conditions on biofilm formation and the cell surface hydrophobicity in fluconazole susceptible and tolerant Candida albicans

The influence of acidic (5.6) and neutral (7.0) pH and glucose concentrations (0.9 and 2 %) was determined in in vitro biofilm formation and the cell surface hydrophobicity (CSH) in fluconazole (FLC) susceptible and tolerant yeasts of Candida albicans. The determination of biofilm viability using tetrazolium salt XTT showed that both FLC-tolerant C. albicans 1173 and FLC-sensitive C. albicans SC 5314 formed more robust biofilm in the YNB medium at pH 7.0 in the absence of FLC than that at acidic pH. Tested glucose concentrations did not show any direct effect on formation of biofilm under all conditions. However, determination of biofilm dry mass that contains also extracellular matrix suggested some effect of 2 % D-glucose. An increase in CSH (for about 10 %) was estimated in C. albicans SC 5314 in the presence of FLC, while the FLC-tolerant isolate proved a weak increase of CSH only in the YNB media containing 2 % D-glucose. Additionally, strain C. albicans SC 5314 strongly flocculated at neutral pH in the absence of FLC, but this phenomenon was not observed in the presence of FLC. Subinhibitory concentration of FLC influenced biofilm cells and CSH, but FLC susceptibility versus tolerance of C. albicans tested strains did not directly affect biofilm formation and/or CSH.