Increasing Fluconazole Resistance in Candida parapsilosis: A 10-Year Analysis of Blood Culture Isolates at a US Reference Laboratory (2015–2024)

Abstract Antifungal susceptibility testing among 1,740 Candida parapsilosis blood isolates submitted to a U.S. reference laboratory (2015–2024) revealed a significant increase in fluconazole resistance from 8.2% to 20.3% (odds ratio [OR] per year: 1.13; 95% confidence interval [CI]: 1.06–1.20; p<0.001), with notable acceleration since 2021. Voriconazole resistance remained stable over this period. Micafungin resistance was rare, but intermediate susceptibility significantly increased, especially after 2021 (OR per year: 1.42; 95% CI: 1.25–1.63; p<0.001). These findings highlight important recent shifts in antifungal susceptibility among C. parapsilosis isolates, emphasizing the need for ongoing surveillance and stewardship.