Department of Agricultural Microbiology, Aligarh Muslim University, Aligarh, India.
J Antimicrob Chemother. 2012 Mar;67(3):618-21. doi: 10.1093/jac/dkr512. Epub 2011 Dec 13.
The aim of this study was to evaluate four phytocompounds (cinnamaldehyde, citral, eugenol and geraniol) for their in vitro inhibitory activity against pre-formed biofilms of Candida albicans alone or in combination with fluconazole and amphotericin B. These compounds were also tested at subinhibitory concentrations for their ability to inhibit biofilm formation.
The XTT reduction assay, light microscopy and scanning electron microscopy (SEM) were employed to determine the inhibitory effect of the test compounds on biofilms. A chequerboard method was used for combination studies.
Both clinical and reference strains of C. albicans (C. albicans 04 and C. albicans SC5314, respectively) displayed formation of strong biofilms. Pre-formed Candida biofilms showed ≥1024× increased resistance to antifungal drugs and 2× increased resistance to cinnamaldehyde and geraniol, but no increased tolerance of eugenol. The test compounds were more active against pre-formed biofilms than amphotericin B and fluconazole. At 0.5× MIC, eugenol and cinnamaldehyde were the most inhibitory compounds against biofilm formation. Light and electron microscopic studies revealed the deformity of three-dimensional structures of biofilms formed in the presence of sub-MICs of eugenol and cinnamaldehyde. The cell membrane appeared to be the target site of compounds in both planktonic and sessile C. albicans cells, as observed by SEM. Combination studies showed that synergy was highest between eugenol and fluconazole (fractional inhibitory concentration index = 0.14) against pre-formed biofilms of C. albicans SC5314.
Promising antibiofilm activity was displayed by eugenol and cinnamaldehyde, which also showed synergy with fluconazole in vitro. Further evaluation in in vivo systems is required to determine whether these findings can be exploited in treating biofilm-associated candidiasis.
本研究旨在评估四种植物化合物（肉桂醛、柠檬醛、丁香酚和香叶醇）对白色念珠菌形成的生物膜的体外抑制活性，单独或与氟康唑和两性霉素 B 联合使用。还在亚抑制浓度下测试了这些化合物抑制生物膜形成的能力。
采用 XTT 还原法、光镜和扫描电子显微镜（SEM）来确定测试化合物对生物膜的抑制作用。棋盘法用于组合研究。
临床和参考株白色念珠菌（分别为白色念珠菌 04 和白色念珠菌 SC5314）均形成了强生物膜。预先形成的白色念珠菌生物膜对抗真菌药物的耐药性增加了≥1024 倍，对肉桂醛和香叶醇的耐药性增加了 2 倍，但对丁香酚的耐受性没有增加。与两性霉素 B 和氟康唑相比，测试化合物对预形成的生物膜更有效。在 0.5×MIC 时，丁香酚和肉桂醛对生物膜形成的抑制作用最强。光镜和电子显微镜研究显示，在亚 MIC 丁香酚和肉桂醛存在下，生物膜的三维结构发生变形。扫描电镜观察到，化合物的作用靶点似乎是浮游和静止白色念珠菌细胞的细胞膜，无论是在浮游细胞还是在静止细胞中。组合研究表明，丁香酚和氟康唑对白色念珠菌 SC5314 预形成生物膜的协同作用最高（部分抑菌浓度指数=0.14）。
丁香酚和肉桂醛表现出有前景的抗生物膜活性，并且在体外与氟康唑也显示出协同作用。需要在体内系统中进一步评估这些发现是否可以用于治疗生物膜相关的念珠菌病。
