In Vitro Exposure to Increasing Micafungin Concentrations Easily Promotes Echinocandin Resistance in Candida glabrata Isolates

We assessed the in vitro susceptibility of five echinocandin-susceptible Candida glabrata isolates after exposure to micafungin. The direct exposure to plates at different micafungin concentrations resulted in the inhibition of growth at 0.062 mu g/ml. The progressive exposure was performed on plates using 0.031 mu g/ml of micafungin and sequential propagation on plates containing the next 2-fold concentration; the MICs of micafungin and anidulafungin increased sequentially, and all the isolates became echinocandin resistant, showing fks2 mutations.