Multidrug-resistant Candida glabrata strains obtained by induction of anidulafungin resistance in planktonic and biofilm cells

Abstract

Candida glabrata has emerged as a common cause of serious life-threatening fungal infections, largely owing to their low susceptibility to azole antifungals. Recent guidance indicates the use of echinocandins as the first-choice drug for the treatment of systemic infections of C. glabrata; however, C. glabrata resistance to echinocandins is reportedly increasing. Herein, we present the induction of anidulafungin resistance in planktonic and sessile cells of C. glabrata and the development of fluconazole cross-resistance. MICs of 21 clinical C. glabrata strains were determined by a broth microdilution method using anidulafungin and fluconazole. Biofilm formation on a tracheal catheter was determined using 1-× 1-cm2 polyvinyl polychloride catheter fragments. Induction of anidulafungin resistance in planktonic and sessile cells and evaluation of its stability were performed by exposing the strains to successively higher concentrations of the antifungal. The induction resulted in strains strongly resistant to anidulafungin (MICs: 1−2 μg/mL) and fluconazole (≥64 μg/mL). Most of the sessile cells of C. glabrata presented slightly reduced susceptibility compared with the planktonic cells. Clinically, this cross-resistance could lead to therapeutic failure while using fluconazole in patients previously exposed to subinhibitory concentrations of anidulafungin for extended periods.