Species-specific antifungal resistance trends in yeast bloodstream isolates causing candidemia before, during, and after the COVID-19 pandemic: insights from the INVIFAR Mexican multicenter network

Yeast pathogens represent a major cause of bloodstream infections, with a rising prevalence of non-albicans Candida species displaying variable antifungal resistance patterns that complicate clinical management. This study evaluated antifungal susceptibility in 1,154 bloodstream yeast isolates collected from January 2019 to December 2024 through the INVIFAR (Investigación y Vigilancia de la Farmacorresistencia) multicentric network, encompassing hospital laboratories across diverse patient populations. Isolates were stratified into pre-pandemic, pandemic, and post-pandemic periods to assess temporal changes in resistance patterns. Identification and susceptibility testing were performed using automated systems and standardized CLSI methods. Longitudinal analysis of antifungal susceptibility in Candida albicans, Nakaseomyces glabratus, Candida parapsilosis, Candida tropicalis and Issatchenkia orientalis revealed predominantly stable profiles across pre-, during-, and post-pandemic periods. Statistically significant changes were observed in two instances: a post-pandemic decrease in caspofungin resistance for N. glabratus (adj. p = 0.0377) and a reduction in voriconazole resistance in C. parapsilosis (adj. p = 0.0015). Resistance velocity analysis highlighted a rapid increase in itraconazole resistance for C. parapsilosis, while C. albicans and I. orientalis remained susceptible. These results emphasize that selective pressure and clonal expansion can drive significant resistance shifts, underscoring the need for targeted surveillance and antifungal stewardship.