Effects of Serum on In Vitro Susceptibility Testing of Echinocandins

The effects of protein binding on the activities of caspofungin, anidulafungin, and micafungin were evaluated against Candida and Aspergillus species. Adding human serum sharply increased the MICs of micafungin and anidulafungin and modestly affected the MIC of caspofungin. The increase in MICs does not appear consistent with the rate of protein binding for the three compounds.