In vitro activity profiles and temporal trends in reduced susceptibility to azoles in Coccidioides in the United States.

Treatment of symptomatic patients with coccidioidomycosis often involves the use of triazole antifungals. There is concern for reduced susceptibility of Coccidioides to fluconazole, as a high percentage of isolates were previously reported to have elevated fluconazole MICs. We reviewed our recent azole MICs against Coccidioides and examined temporal trends over a 20-year period. Our clinical laboratory database was queried for data against Coccidioides between 2006 and 2025, and trends in GM MICs and the percentage of isolates with elevated MICs to the azoles were assessed. All testing had been performed by broth dilution according to Clinical and Laboratory Standards Institute (CLSI) M38 methods. The results over the 10-year period from 2016 to 2025 were compared to those previously reported by our group from 2001 to 2015. Overall, the results between the two periods showed similar MIC parameters and distributions for fluconazole, itraconazole, posaconazole, and voriconazole, with posaconazole demonstrating the most potent activity, while fluconazole demonstrated reduced susceptibility. Isavuconazole MIC parameters were available during the second period and similar to those of voriconazole. Weak correlations were observed between fluconazole MICs and those of the other azoles. Fluctuations in GM MICs and the percentage of isolates with elevated MICs were observed with fluconazole, itraconazole, and posaconazole, with elevated values observed between 2011 and 2019. Continued surveillance is needed, and outcome data are required to determine if the consistently reduced susceptibility observed with fluconazole or in those infected with strains that have higher MICs results in poorer outcomes in patients with coccidioidomycosis.