Ouyang Jing, Sun Fengjun, Feng Wei, Xie Yonghong, Ren Lijuan, Chen Yongchuan
Department of Pharmacy, Chongqing Public Health Medical Center, Chongqing, China.
Chemotherapy. 2018;63(1):20-28. doi: 10.1159/000481658. Epub 2017 Nov 17.
Backgroud: Antibiotic treatment for infections caused by vancomycin-intermediate Staphylococcus aureus (VISA) strains is challenging, and only a few effective and curative methods have been developed to combat these strains. This study aimed to investigate the antimicrobial activity of galangin against S. aureus and its effects on the murein hydrolases of VISA strain Mu50. This is the first report on these effects of galangin, and it may help to improve the treatment for VISA infections by demonstrating the effective use of galangin.
Firstly, the minimum inhibitory concentration (MIC) and growth curve were used to investigate the antimicrobial activity of galangin against S. aureus. Secondly, transmission electron microscopy (TEM) was used to observe morphological changes of VISA strain Mu50. Thirdly, Triton X-100-induced autolysis and cell wall hydrolysis assays were performed to determine the activities of the murein hydrolases of Mu50. Finally, fluorescence real-time quantitative PCR was used to investigate the expression of the murein hydrolase-related Mu50 genes.
The results indicated that the MIC of galangin was 32 μg/mL against ATCC25293, N315, and Mu50, and galangin could significantly suppress the bacterial growth (p < 0.05) with concentrations of 4, 8 and 16 μg/mL, compared with control group (0 μg/mL). To explore the possible reasons of bacteriostatic effects of galangin, we observed morphological changes using TEM which showed that the division of Mu50 daughter cells treated with galangin was obviously inhibited. Considering the vital role of murein hydrolases in cellular division, assays were performed, and galangin markedly decreased Triton X-100-induced autolysis and cell wall hydrolysis. Galangin also significantly inhibited the expression of the murein hydrolase genes (atl, lytM, and lytN) and their regulatory genes (cidR, cidA, and cidB).
Our findings indicated that galangin can effectively inhibit murein hydrolase activity as well as the growth of VISA strain Mu50.
背景：针对万古霉素中介金黄色葡萄球菌（VISA）菌株引起的感染进行抗生素治疗具有挑战性，目前仅开发出少数几种有效的治疗方法来对抗这些菌株。本研究旨在探究高良姜素对金黄色葡萄球菌的抗菌活性及其对VISA菌株Mu50的胞壁质水解酶的影响。这是关于高良姜素这些作用的首次报道，通过证明高良姜素的有效利用，可能有助于改善VISA感染的治疗。
首先，使用最低抑菌浓度（MIC）和生长曲线来研究高良姜素对金黄色葡萄球菌的抗菌活性。其次，使用透射电子显微镜（TEM）观察VISA菌株Mu50的形态变化。第三，进行Triton X-100诱导的自溶和细胞壁水解试验，以确定Mu50的胞壁质水解酶的活性。最后，使用荧光实时定量PCR研究与胞壁质水解酶相关的Mu50基因的表达。
结果表明，高良姜素对ATCC25293、N315和Mu50的MIC为32μg/mL，与对照组（0μg/mL）相比，浓度为4、8和16μg/mL的高良姜素可显著抑制细菌生长（p<0.05）。为探究高良姜素抑菌作用的可能原因，我们使用TEM观察形态变化，结果显示用高良姜素处理的Mu50子细胞的分裂明显受到抑制。考虑到胞壁质水解酶在细胞分裂中的重要作用，进行了相关试验，结果显示高良姜素显著降低了Triton X-100诱导的自溶和细胞壁水解。高良姜素还显著抑制了胞壁质水解酶基因（atl、lytM和lytN）及其调控基因（cidR、cidA和cidB）的表达。
我们的研究结果表明，高良姜素可有效抑制VISA菌株Mu50的胞壁质水解酶活性以及其生长。
