表儿茶素没食子酸酯与四环素协同抗金黄色葡萄球菌作用及机制

Synergetic antibacterial effects of epicatechin gallate and tetracycline against Staphylococcus aureus and their mechanism

目的研究表儿茶素没食子酸酯(ECg)与四环素对耐甲氧西林金黄色葡萄球菌(MRSA)和敏感菌(MSSA)的协同抗菌作用并探讨其机制。方法以微量稀释法测定ECg与四环素的体外抗MRSA(15株MRSA)和MSSA(ATCC25923)的协同作用。以荧光法测定ECg对金黄色葡萄球菌的tet(K)四环素外排泵抑制作用。结果ECg对MRSA和ATCC25923的最小抑菌浓度(MIC)均为256mg·L^(-1);四环素对MRSA的MIC值为2～128 mg·L^(-1),对ATCC25923为2 mg·L^(-1)。合用25mg·L^(-1)ECg与四环素后,15株MRSA中有5株呈协同作用,7株呈相加作用,2株呈无关作用,1株呈拮抗作用;而ATCC25923呈相加作用。经50 mg·L^(-1)ECg和100 mg·L^(-1)四环素处理过的tet(K)阳性株(MRSA-2)对四环素的外排作用低于单用100 mg·L^(-1)四环素处理的菌株,而经ECg和四环素处理过的tet(K)阴性株(ATCC25923)对四环素的外排作用与单用四环素处理的菌株基本相同。结论ECg与四环素对金黄色葡萄球菌主要呈协同或相加作用,其机制可能为抑制其四环素外排泵。

AIM To study the synergetic antibacterial effects of epicatechin gallate （ECg） and tetracycline against methicillin-resistant Staphylococcus aureus （MRSA） and methicillin-sensitive Staphylococcus aureus （MSSA） and their mechanism. METHODS Synergistic effects of ECg and tetracycline in vitro against MRSA （15 MRSA strains） and MSSA （ATCC25923） were detected by microdilution method. The inhibition of tet（K） efflux pump by ECg were determined by spectrofluorometric assays. RESULTS The MICs of ECg against MRSA and ATCC25923 were both 256 mg.L-1, MIC range of tetracycline against MRSA was 2 - 128 mg.L-1,and MIC of tetracycline against MSSA was 2 mg.L-1. Combined with 25 mg.L-1 ECg and tetracycline, synergic effect was found in five MRSA strains, additive effect was found in seven MRSA strains and the ATCC25923 strains, independent effect was found in two MRSA strains, and antagonist effect was found in one MRSA strain. The tetracycline exoeytosis of tet （K）-positive strain （MRSA-2） treated by 50 mg.L-1 ECg and 100 mg.L-1 tetracycline was significantly lower than the strains treated by 100 mg.L-1 tetracycline alone, While the tetracycline exocytosis of tet （ K） -negative strain （ATCC25923） treated by 50 mg.L-1 ECg and 100 mg.L-1 tetracycline was the same as the strains treated by 100 mg.L-1 tetracycline alone. CONCLUSION ECg showed synergistic or additive effects with tetracycline mainly against Staphylococcus aureu and this might be associated with the inhibition of tetracycline efflux pump.