ABSTRACT

Candida auris has emerged as a fungal pathogen that causes nosocomial outbreaks worldwide. Diseases caused by this fungus are of concern, due to its reduced susceptibility to several antifungals. C. auris exhibits paradoxical growth (PG; defined as growth at high, but not intermediate antifungal concentrations) in the presence of caspofungin (CPF). We have characterized the cellular changes associated with adaptation to CPF. Using EUCAST AFST protocols, all C. auris isolates tested showed PG to CPF, although in some isolates it was more prominent. Most isolates also showed a trailing effect (TE) to micafungin and anidulafungin. We identified two FKS genes in C. auris that encode the echinocandins target, namely β-1,3-glucan synthase. FKS1 contained the consensus hot-spot (HS) 1 and HS2 sequences. FKS2 only contained the HS1 region which had a change (F635Y), that has been shown to confer resistance to echinocandins in C. glabrata. PG has been characterized in other species, mainly C. albicans, where high CPF concentrations induced an increase in chitin, cell volume and aggregation. In C. auris CPF only induced a slight accumulation of chitin, and none of the other phenomena. RNAseq experiments demonstrated that CPF induced the expression of genes encoding several GPI-anchored cell wall proteins, membrane proteins required for the stability of the cell wall, chitin synthase and mitogen-activated protein kinases (MAPKs) involved in cell integrity, such as BCK2, HOG1 and MKC1 (SLT2). Our work highlights some of the processes induced in C. auris to adapt to echinocandins.

摘要

耳念珠菌已成为一种真菌病原体，导致世界范围内的医院内暴发。由于这种真菌对几种抗真菌药物的敏感性降低，因此引起的疾病值得关注。在卡泊芬净(CPF) 存在下，耳念珠菌表现出反常生长（PG；定义为在高抗真菌浓度下生长，但不在中等抗真菌浓度下生长）。我们已经描述了与 CPF 适应相关的细胞变化。使用 EUCAST AFST 方案，所有测试的耳念珠菌分离株均显示 PG 至 CPF，尽管在某些分离株中更为突出。大多数分离株还显示出对米卡芬净和阿尼芬净的拖尾效应 (TE)。我们在耳念珠菌中鉴定出两个编码棘白菌素靶标的FKS基因，即 β-1,3-葡聚糖合酶。FKS1包含共有热点 (HS) 1 和 HS2 序列。FKS2仅包含发生变化的 HS1 区域 (F635Y)，该变化已被证明赋予光滑念珠菌中的棘白菌素抗性。PG 已在其他物种中得到表征，主要是白色念珠菌，其中高 CPF 浓度诱导几丁质、细胞体积和聚集的增加。在耳念珠菌中，CPF仅诱导轻微的几丁质积累，没有其他现象。RNAseq 实验表明，CPF 诱导编码多种 GPI 锚定细胞壁蛋白、细胞壁稳定性所需的膜蛋白、几丁质合酶和参与细胞完整性的丝裂原激活蛋白激酶 (MAPK) 的基因表达，例如 BCK2 、 HOG1和MKC1 ( SLT2 )。我们的工作重点介绍了耳念珠菌中诱导适应棘白菌素的一些过程。