Inhibition of Nucleic Acid Biosynthesis Makes Little Difference to Formation of Amphotericin B-Tolerant Persisters in Candida albicans Biofilm
ABSTRACTCandida albicanspersisters constitute a small subpopulation of biofilm cells and play a major role in recalcitrant chronic candidiasis; however, the mechanism underlying persister formation remains unclear. Persisters are often described as dormant, multidrug-tolerant, nongrowing cells. Persister cells are difficult to isolate and study not only due to their low levels inC. albicansbiofilms but also due to their transient, reversible phenotype. In this study, we tried to induce persister formation by inducingC. albicanscells into a dormant state.C. albicanscells were pretreated with 5-fluorocytosine (planktonic cells, 0.8 μg ml−1; biofilm cells, 1 μg ml−1) for 6 h at 37°C, which inhibits nucleic acid and protein synthesis. Biofilms and planktonic cultures of eightC. albicansstrains were surveyed for persisters after amphotericin B treatment (100 μg ml−1for 24 h) and CFU assay. None of the planktonic cultures, with or without 5-fluorocytosine pretreatment, contained persisters. Persister cells were found in biofilms of all testedC. albicansstrains, representing approximately 0.01 to 1.93% of the total population. However, the persister levels were not significantly increased inC. albicansbiofilms pretreated with 5-fluorocytosine. These results suggest that inhibition of nucleic acid synthesis did not seem to increase the formation of amphotericin B-tolerant persisters inC. albicansbiofilms.