Department of Clinical Laboratory, Obstetrics and Gynecology Hospital of Fudan University, 419 Fangxie Road, Shanghai 200011, China.
Unit of Pathogenic Fungal Infection and Host Immunity, CAS Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China.
FEMS Yeast Res. 2017 May 1;17(3). doi: 10.1093/femsyr/fox012.
The increasing prevalence of azole resistance in Candida albicans poses a growing problem for clinical treatment. Amino acid substitution of the 14α-demethylase (Erg11p) encoded by the ERG11 gene is one of the most common mechanisms involved in azole resistance. Although amino acid substitutions of Erg11p have been observed in many clinical isolates, only a few amino acid substitutions have been confirmed to be related to azole resistance. In this study, by amplifying and sequencing the open reading frame of the ERG11 gene from 55 clinical isolates, we identified 27 fluconazole-resistant isolates that harbor a novel amino acid substitution, T123I, in Erg11p, in addition to the previously described homozygous substitution Y132H. We investigated both the contribution of this novel substitution T123I and its synergistic effect with substitution Y132H to azole resistance by heterogeneously expressing the C. albicans Erg11p with different substitution forms in Saccharomyces cerevisiae. Results showed that S. cerevisiae cells harboring the substitution T123I displayed higher (4-fold) minimum inhibitory concentration values to both fluconazole and voriconazole than the cells expressing the wild-type version of C. albicans Erg11p, but this was not true for itraconazolele. More importantly, a synergistic effect of substitutions T123I and Y132H was observed in an assay of voriconazole resistance. These results indicate that amino acid substitutions of Erg11p are prevalent among azole-resistant isolates and that the substitution T123I confers resistance to both fluconazole and voriconazole.
白色念珠菌中唑类药物耐药性的不断增加给临床治疗带来了越来越大的问题。14α-去甲基酶（Erg11p）编码基因 ERG11 中氨基酸的取代是唑类耐药性涉及的最常见机制之一。尽管在许多临床分离株中已经观察到 Erg11p 的氨基酸取代，但只有少数氨基酸取代被证实与唑类耐药性有关。在这项研究中，通过扩增和测序 55 株临床分离株的 ERG11 基因开放阅读框，我们在除先前描述的纯合取代 Y132H 之外，还在 27 株氟康唑耐药株中鉴定出 Erg11p 中的新型氨基酸取代 T123I。我们通过在酿酒酵母中异源表达具有不同取代形式的 C. albicans erg11p 来研究这种新型取代 T123I 的贡献及其与取代 Y132H 的协同作用对唑类耐药性的影响。结果表明，与表达 C. albicans erg11p 野生型的酵母细胞相比，携带取代 T123I 的酵母细胞对氟康唑和伏立康唑的最小抑菌浓度值分别高出 4 倍，但对伊曲康唑则不然。更重要的是，在伏立康唑耐药性测定中观察到取代 T123I 和 Y132H 的协同作用。这些结果表明，唑类耐药分离株中 Erg11p 的氨基酸取代很常见，取代 T123I 赋予对氟康唑和伏立康唑的耐药性。
