Evaluation of direct antifungal susceptibility testing using E-test for four antifungal agents in candidemia patients

Candidemia is associated with high morbidity and mortality. Delayed initiation of effective and appropriate antifungal therapy correlates with increased patient mortality, emphasizing the importance of rapid antifungal susceptibility testing (AFST). Usual commercial methods as standard E-test are time-consuming, often requiring a minimum of 48 hours. This study aimed to evaluate the performance of direct E-test (ET-dir) directly from positive blood culture bottles, with the goal of reducing turnaround time and improving clinical decision-making. A total of 160 yeast positive blood cultures were included over a four-year period, comprising 85 Candida albicans. The minimum inhibitory concentrations (MICs) of fluconazole, voriconazole, amphotericin B, and anidulafungin were determined using ET-dir and compared to ET method (ET-sd). Essential agreement, categorical agreement, error rates and bias were analyzed for all species and specifically for C. albicans. The essential agreement between ET-dir and ET-sd exceeded 87% for all antifungal agents and reached ≥90% for fluconazole. The categorical agreement was above 90% for all agents, and error rates remained within acceptable limits except for anidulafungin. For C. albicans, 23 of 24 performance data met acceptability criteria, with essential agreement ≥90% for all agents except fluconazole. ET-dir results were interpretable within 24 hours for 93.7% of strains, providing at least a 24-hour time gain over ET-sd. ET-dir is a reliable and rapid AFST method for candidemia, meeting most performance criteria compared to ET-sd while significantly reducing turnaround time. Its routine implementation could enable faster adaptation of antifungal therapy, ensuring that treatments are optimized based on susceptibility results.