Establishment and evaluation of standard strains of azole antifungal drug-resistant Candida albicans

Objective Establishing a standard strain of Candida albicans (C. albicans), a resistant azole antifungal drug, and conducting the preservation work of pathogenic microbial strains according to the Technical Requirements for Evaluation of National Standard Strains of Pathogenic Microorganisms (WS/T 812—2022), will provide a standardized reference method for other fungal standard strains in the future.

Methods Assess the phenotypic stability and activity of strain preservation through phenotypic characterization, identification, and testing of sensitivity to nine antifungal drugs and resistance genes.

Results Through internal transcribed spacer (ITS) sequence analysis and Matrix assisted laser desorption/ionization-Time of flight mass spectrometry (MALDI-TOF MS), the strain was confirmed to be C. albicans. The strain maintained stable molecular characteristics following ten sequential passages. The minimum inhibitory concentrations (MICs) of the strain to fluconazole, voriconazole, itraconazole, and posaconazole were 16 mg/L, 0.5 mg/L, 0.5 mg/L, and 0.5 mg/L, respectively. Its resistance was associated with mutations in the ERG11 gene (A114S, Y257H) and the drug efflux pump-encoding gene (A736V). The strain could be stably preserved at –80 ℃ for at least 6 months.

Conclusion This study established a standardized strain of Candida albicans for antifungal drugs in the azole class, providing a crucial research subject and material foundation for the comprehensive prevention and treatment of Candida albicans infectious diseases. This carries significant strategic importance for national biosecurity.