Shah S, Stapleton P D, Taylor P W
School of Pharmacy, University of London, London, UK.
Lett Appl Microbiol. 2008 Feb;46(2):181-5. doi: 10.1111/j.1472-765X.2007.02296.x. Epub 2007 Dec 7.
(-)-epicatechin gallate (ECg) modifies the morphology, cell wall architecture and beta-lactam antibiotic susceptibility of Staphylococcus aureus. As these effects result primarily from intercalation into the bacterial cytoplasmic membrane, the capacity of ECg to modulate the secretion of two key staphylococcal virulence factors, coagulase and alpha-toxin, was examined.
Bioassays were used to determine coagulase and haemolysin activity in culture supernatants of a number of S. aureus isolates grown in the presence and absence of ECg; alpha-toxin secretion was also evaluated by immunoblotting. Growth in ECg reduced the levels of activity of both proteins in culture supernatants; the effects could only be partly explained by ECg-mediated inhibition of bioactivity and by induction of secreted proteases.
ECg suppresses the secretion of coagulase and alpha-toxin by clinical isolates of S. aureus.
The observation that secretion of key components of staphylococcal virulence can be compromised by a naturally occurring polyphenol supports the notion that ECg and related compounds may have therapeutic utility for the control of infections that are currently difficult to treat due to the propensity of methicillin-resistant S. aureus to accumulate antibiotic resistance genes.
（-）-表儿茶素没食子酸酯（ECg）可改变金黄色葡萄球菌的形态、细胞壁结构及对β-内酰胺类抗生素的敏感性。由于这些作用主要是通过插入细菌细胞质膜产生的，因此研究了ECg调节两种关键葡萄球菌毒力因子凝固酶和α-毒素分泌的能力。
采用生物测定法测定在有无ECg存在的情况下培养的多种金黄色葡萄球菌分离株培养上清液中的凝固酶和溶血素活性；还通过免疫印迹法评估α-毒素的分泌。在ECg中生长可降低培养上清液中两种蛋白质的活性水平；这些作用只能部分由ECg介导的生物活性抑制和分泌蛋白酶的诱导来解释。
ECg可抑制金黄色葡萄球菌临床分离株凝固酶和α-毒素的分泌。
天然存在的多酚可损害葡萄球菌毒力关键成分的分泌这一观察结果支持了以下观点，即ECg及相关化合物可能具有治疗用途，可用于控制因耐甲氧西林金黄色葡萄球菌易于积累抗生素耐药基因而目前难以治疗的感染。
