Ayed A, Essid R, Mankai H, Echmar A, Fares N, Hammami M, Sewald N, Limam F, Tabbene O
Laboratory of Bioactive Substances, Center of Biotechnology of Borj Cedria, BP 901, Hammam-Lif 2050, Tunisia.
Laboratory of Aromatic and Medicinal Plants, Center of Biotechnology of Borj Cedria, Hammam-Lif 2050, Tunisia.
J Appl Microbiol. 2023 Nov 1;134(11). doi: 10.1093/jambio/lxad246.
The present study aimed to investigate a novel antifungal compound produced by Streptomyces blastmyceticus S108 strain. Its effectiveness against clinical isolates of Candida species and its synergistic effect with conventional antifungal drugs were assessed, and its molecular mechanism of action was further studied against Candida albicans.
A newly isolated strain from Tunisian soil, S. blastmyceticus S108, showed significant antifungal activity against Candida species by well diffusion method. The butanolic extract of S108 strain supernatant exhibited the best anti-Candida activity with a minimal inhibitory concentration (MIC) value of 250 μg ml-1, determined by the microdilution method. The bio-guided purification steps of the butanolic extract were performed by chromatographic techniques. Among the fractions obtained, F13 demonstrated the highest level of activity, displaying a MIC of 31.25 μg ml-1. Gas chromatography-mass spectrometry and electrospray ionization mass spectrometry analyses of this fraction (F13) revealed the glycolipidic nature of the active molecule with a molecular weight of 685.6 m/z. This antifungal metabolite remained stable to physicochemical changes and did not show hemolytic activity even at 4MIC corresponding to 125 µg ml-1 toward human erythrocytes. Besides, the glycolipid compound was combined with 5-flucytosine and showed a high synergistic effect with a fractional inhibitory concentration index value 0.14 against C. albicans ATCC 10231. This combination resulted in a decrease of MIC values of 5-flucytosine and the glycolipid-like compound by 8- and 64-fold, respectively. The examination of gene expression in treated C. albicans cells by quantitative polymerase chain reaction (qPCR) revealed that the active compound tested alone or in combination with 5-flucytosine blocks the ergosterol biosynthesis pathway by downregulating the expression of ERG1, ERG3, ERG5, ERG11, and ERG25 genes.
The new glycolipid-like compound, produced by Streptomyces S108 isolate, could be a promising drug for medical use against pathogenic Candida isolates.
本研究旨在探究由产芽生菌链霉菌S108菌株产生的一种新型抗真菌化合物。评估其对念珠菌属临床分离株的有效性及其与传统抗真菌药物的协同作用，并进一步研究其针对白色念珠菌的分子作用机制。
从突尼斯土壤中新分离出的菌株产芽生菌链霉菌S108，通过滤纸片扩散法对念珠菌属显示出显著的抗真菌活性。通过微量稀释法测定，S108菌株上清液的丁醇提取物表现出最佳的抗念珠菌活性，最低抑菌浓度（MIC）值为250μg/ml。丁醇提取物的生物导向纯化步骤通过色谱技术进行。在获得的馏分中，F13表现出最高水平的活性，MIC为31.25μg/ml。对该馏分（F13）进行气相色谱-质谱联用和电喷雾电离质谱分析，揭示了活性分子的糖脂性质，分子量为685.6 m/z。这种抗真菌代谢产物对物理化学变化保持稳定，即使在相当于125μg/ml的4倍MIC浓度下对人红细胞也未显示溶血活性。此外，该糖脂化合物与5-氟胞嘧啶联合使用，对白色念珠菌ATCC 10231表现出高协同效应，分级抑菌浓度指数值为0.14。这种联合使用分别使5-氟胞嘧啶和类糖脂化合物的MIC值降低了8倍和64倍。通过定量聚合酶链反应（qPCR）检测经处理的白色念珠菌细胞中的基因表达，结果显示单独测试或与5-氟胞嘧啶联合使用的活性化合物通过下调ERG1、ERG3、ERG5、ERG11和ERG25基因的表达来阻断麦角固醇生物合成途径。
由产芽生菌链霉菌S108分离株产生的新型类糖脂化合物可能是一种有前景的医用药物，用于对抗致病性念珠菌分离株。
