X Fan1, M Xiao2, D Zhang2, J-J Huang2, H Wang2, X Hou2, L Zhang2, F Kong3, S C-A Chen3, Z-H Tong4, Y-C Xu5. 1. Department of Infectious Diseases and Clinical Microbiology, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China; Department of Clinical Laboratory, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China; Beijing Key Laboratory for Mechanisms Research and Precision Diagnosis of Invasive Fungal Diseases, Beijing, China. 2. Department of Clinical Laboratory, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China; Beijing Key Laboratory for Mechanisms Research and Precision Diagnosis of Invasive Fungal Diseases, Beijing, China. 3. Centre for Infectious Diseases and Microbiology Laboratory Services, ICPMR, New South Wales Health Pathology, Westmead Hospital, The University of Sydney, Australia. 4. Department of Respiratory and Critical Care Medicine, Beijing Institute of Respiratory Medicine, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China. Electronic address: tongzhaohuicy@sina.com. 5. Department of Clinical Laboratory, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China; Beijing Key Laboratory for Mechanisms Research and Precision Diagnosis of Invasive Fungal Diseases, Beijing, China. Electronic address: xycpumch@139.com.
Abstract
OBJECTIVE: We investigated molecular mechanisms responsible for azole resistance in Candida tropicalis isolates. METHODS: We studied 507 C. tropicalis isolates causing invasive candidiasis from ten hospitals over 5 years. Antifungal susceptibility was determined by broth microdilution methods. Point mutations in the C. tropicalis ERG11 gene that may confer azole resistance were explored and verified. The expression levels of ERG11, CYTb, MDR1 and CDR1 genes were compared in 20 fluconazole-susceptible and 20 fluconazole-resistant isolates. RESULTS: Fluconazole-susceptible, -susceptible dose-dependent and -resistant strains accounted for 76.7% (389/507), 10.5% (53/507) and 12.8% (65/507) of C. tropicalis isolates, respectively. The ERG11 mutation A395T/W occurred in 10.7% (54/507) of isolates, all of which were resistant to fluconazole. The nucleotide mutation C461T/Y was the second most common (50/507 isolates, 9.9%), and all isolates carrying C461T/Y also had the mutation A395T/W. However, the presence of C461T did not contribute to the azole-resistant phenotype. Substitutions V125A, Y257H and G464S (<2% of isolates), which were reported for the first time in C. tropicalis, also conferred fluconazole non-susceptible phenotypes. Compared with fluconazole susceptible isolates, fluconazole-resistant isolates had higher ERG11 (fold expression level 1.42 versus 0.79, p < 0.01) but lower CYTb (fold expression level 1.26 versus 2.67, p < 0.01) gene expression levels. Three azole-resistant isolates carrying the wild-type ERG11 gene had higher levels of CDR1 and MDR1 expression. CONCLUSIONS: ERG11 missense mutations were the major mechanism responsible for azole resistance in C. tropicalis isolates, but overexpression of ERG11, CDR1 and MDR1, as well as reduced expression of CYTb, also contributed to resistance.
OBJECTIVE: We investigated molecular mechanisms responsible for azole resistance in Candida tropicalis isolates. METHODS: We studied 507 C. tropicalis isolates causing invasive candidiasis from ten hospitals over 5 years. Antifungal susceptibility was determined by broth microdilution methods. Point mutations in the C. tropicalis ERG11 gene that may confer azole resistance were explored and verified. The expression levels of ERG11, CYTb, MDR1 and CDR1 genes were compared in 20 fluconazole-susceptible and 20 fluconazole-resistant isolates. RESULTS:Fluconazole-susceptible, -susceptible dose-dependent and -resistant strains accounted for 76.7% (389/507), 10.5% (53/507) and 12.8% (65/507) of C. tropicalis isolates, respectively. The ERG11 mutation A395T/W occurred in 10.7% (54/507) of isolates, all of which were resistant to fluconazole. The nucleotide mutation C461T/Y was the second most common (50/507 isolates, 9.9%), and all isolates carrying C461T/Y also had the mutation A395T/W. However, the presence of C461T did not contribute to the azole-resistant phenotype. Substitutions V125A, Y257H and G464S (<2% of isolates), which were reported for the first time in C. tropicalis, also conferred fluconazole non-susceptible phenotypes. Compared with fluconazole susceptible isolates, fluconazole-resistant isolates had higher ERG11 (fold expression level 1.42 versus 0.79, p < 0.01) but lower CYTb (fold expression level 1.26 versus 2.67, p < 0.01) gene expression levels. Three azole-resistant isolates carrying the wild-type ERG11 gene had higher levels of CDR1 and MDR1 expression. CONCLUSIONS: ERG11 missense mutations were the major mechanism responsible for azole resistance in C. tropicalis isolates, but overexpression of ERG11, CDR1 and MDR1, as well as reduced expression of CYTb, also contributed to resistance.
Authors: Martin Hoenigl; Rosanne Sprute; Amir Arastehfar; John R Perfect; Cornelia Lass-Flörl; Romuald Bellmann; Juergen Prattes; George R Thompson; Nathan P Wiederhold; Mohanad M Al Obaidi; Birgit Willinger; Maiken C Arendrup; Philipp Koehler; Matteo Oliverio; Matthias Egger; Ilan S Schwartz; Oliver A Cornely; Peter G Pappas; Robert Krause Journal: Expert Opin Investig Drugs Date: 2022-06-15 Impact factor: 6.498