Rapid Acquisition of Stable Azole Resistance by Candida glabrata Isolates Obtained before the Clinical Introduction of Fluconazole

Five azole-susceptible Candida glabrata isolates obtained before 1975 became resistant to fluconazole, itraconazole, and voriconazole within 4 days of in vitro fluconazole exposure. This cross-resistance was stable for at least 4 months after removal of fluconazole and was associated with increased CgCDR1 and CgCDR2 expression.