Fungal Resistance to Echinocandins and the MDR Phenomenon in .

has thoroughly adapted to successfully colonize human mucosal membranes and survive in vivo pressures. prior to and during antifungal treatment. Out of all the medically relevant species, has emerged as a leading cause of azole, echinocandin, and multidrug (MDR: azole + echinocandin) adaptive resistance. Neither mechanism of resistance is intrinsic to , since stable genetic resistance depends on mutation of drug target genes, and (echinocandin resistance), and a transcription factor, , which controls expression of major drug transporters, such as (azole resistance). However, another hallmark of is the ability to withstand drug pressure both in vitro and in vivo prior to stable "genetic escape". Additionally, these resistance events can arise within individual patients, which underscores the importance of understanding how this fungus is adapting to its environment and to drug exposure in vivo. Here, we explore the evolution of echinocandin resistance as a multistep model that includes general cell stress, drug adaptation (tolerance), and genetic escape. The extensive genetic diversity reported in is highlighted.