In vitro activity of caspofungin (MK-0991) against Candida albicans clinical isolates displaying different mechanisms of azole resistance

Caspofungin inhibits the synthesis of 1,3-β-D-glucan, a key step in fungal cell wall biosynthesis. Here we report on its potent in vitro activity (MIC at which 90% of the isolates tested are inhibited = 1 μg per ml of RPMI medium) against 32 Candida albicans fluconazole-susceptible and -resistant clinical isolates irrespective of the underlying resistance mechanism (alterations in ERG11 and/or upregulation of MDR and CDR genes encoding efflux pumps) and provide further evidence that caspofungin is not a substrate for multidrug transporters.