Li Zhen, Yin Hongmei, Chen Weiqin, Jiang Cen, Hu Jun, Xue Yingjun, Yao Dongting, Peng Yibing, Hu Xiaobo
Department of Laboratory Medicine, Longhua Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, People's Republic of China.
Department of Laboratory Medicine, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, People's Republic of China.
Infect Drug Resist. 2020 Aug 5;13:2733-2743. doi: 10.2147/IDR.S261299. eCollection 2020.
Candida tropicalis () has emerged as an important fungal pathogen due to its increasing resistance to conventional antifungal agents, especially fluconazole (FLC). Pseudolaric acid B (PAB), a herbal-originated diterpene acid from Pseudolarix kaempferi Gordon, has been reported to possess inhibitory activity against fungus. The present study aims to investigate the antifungal effect of PAB alone and in combination with FLC on planktonic and biofilm cells of .
The antifungal activity of PAB against planktonic isolates was evaluated alone and in combination with FLC using the chequerboard microdilution method and growth curve assay. The anti-biofilm effects were quantified by tetrazolium (XTT) reduction assay, which were further confirmed by scanning electron microscopy (SEM) and fluorescent microscope to observe morphological changes of biofilm treated with PAB and FLC.
It was revealed that PAB alone exhibited similar inhibitory activity against FLC-resistant and FLC-susceptible strains with median MIC ranging from 8 to 16 µg/mL. When administered in combination, synergism was observed in all (13/13) FLC-resistant and (2/9) FLC-susceptible strains with FICI ranging from 0.070 to 0.375. Moreover, the concomitant use of PAB and FLC exhibited a strong dose-dependent synergistic inhibitory effect on the early and mature biofilm, eliminating more than 80% biofilm formation. SEM found that PAB, different from azoles, could significantly inhibit spore germination and destroy the cell integrity causing cell deformation, swelling, collapse and outer membrane perforation.
PAB was highly active against FLC-resistant isolates and biofilm of particularly when combined with FLC. These findings suggest that PAB may have potential as a novel antifungal agent with different targets from azole drugs.
热带假丝酵母（）由于对传统抗真菌药物尤其是氟康唑（FLC）的耐药性不断增加，已成为一种重要的真菌病原体。土槿皮酸B（PAB）是一种源自金钱松的草药二萜酸，据报道具有抗真菌活性。本研究旨在探讨PAB单独及与FLC联合对热带假丝酵母浮游细胞和生物膜细胞的抗真菌作用。
采用棋盘微量稀释法和生长曲线分析法，单独及联合FLC评估PAB对浮游分离株的抗真菌活性。通过四氮唑（XTT）还原试验对生物膜的抗生物膜作用进行定量，并用扫描电子显微镜（SEM）和荧光显微镜进一步证实，以观察经PAB和FLC处理的生物膜的形态变化。
结果显示，PAB单独对氟康唑耐药和敏感菌株均表现出相似的抑制活性，中位MIC范围为8至16μg/mL。联合使用时，在所有（13/13）氟康唑耐药菌株和（2/9）氟康唑敏感菌株中均观察到协同作用，FICI范围为0.070至0.375。此外，PAB与FLC联合使用对早期和成熟生物膜均表现出强烈的剂量依赖性协同抑制作用，并消除了超过80%的生物膜形成。SEM发现，与唑类不同，PAB可显著抑制孢子萌发并破坏细胞完整性，导致细胞变形、肿胀、塌陷和外膜穿孔。
PAB对氟康唑耐药菌株和热带假丝酵母生物膜具有高度活性，尤其是与FLC联合使用时。这些发现表明，PAB可能具有作为一种与唑类药物靶点不同的新型抗真菌药物的潜力。
