[Bactericidal and anti-toxin activities of catechin on enterohemorrhagic Escherichia coli].
[Bactericidal and anti-toxin activities of catechin on enterohemorrhagic Escherichia coli].
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儿茶素对肠出血性大肠杆菌的杀菌和抗毒素活性[J].
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发表时间：
1998
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通讯作者：
T. Shimamura
中科院分区：
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作者：
S. Okubo;T. Sasaki;Y. Hara;F. Mori;T. Shimamura
我们研究了儿茶素的杀菌活性，茶的收敛成分，对肠出血性大肠杆菌（EHEC）O 157：H7和抗毒素活性的儿茶素对Vero毒素（VT），EHEC O 157：H7的主要致病因子。为了检测杀菌活性，我们将1 × 10（4）CFU/ml细菌加入到1.25至20 W/V%的绿色茶提取物或含有25至400微克/ml的（-）表没食子儿茶素没食子酸酯（EGCg）（其是绿色茶叶的主要儿茶素成分）的PBS溶液中，并在不同的时间间隔计数活细菌的数量。3至5小时后，在1.25至2.5%（常规饮用浓度）的绿色茶提取物中没有观察到活细菌。在100至400微克/毫升EGCg的高浓度下，活细菌的数量随时间而减少，24小时后没有观察到存活者。然而，在25至50微克/毫升EGCg的低浓度下，在5小时内没有观察到活细菌数量的变化。24小时后，50微克/毫升的细菌被杀死，25微克/毫升的细菌数量减少到开始时的十分之一。为了检测抗毒素活性，我们在体外混合等体积的2ng/0.1ml VT 2和0.5至2 mg/0.1ml儿茶素，并将它们在37 ℃下孵育不同的时间。将0.2ml混合液接种BALB/c小鼠。1 mg儿茶素可100%抑制2ng维生素T2对小鼠的致死毒性（LD 100）。儿茶素对VT_2致死毒性的抑制作用具有时间依赖性。孵育9、12和18-24小时的抑制率分别为0、40和100%。这些结果表明，儿茶素不仅对EHEC O 157：H7具有杀菌活性，而且对Vero毒素具有抗毒素活性。
We examined the bactericidal activity of catechin, an astringent ingredient of tea, on enterohemorrhagic Escherichia coli (EHEC) O157:H7 and the anti-toxin activity of catechin on vero toxin (VT), the main pathogenic factor of EHEC O157:H7. To examine bactericidal activity, we added 1 X 10(4) CFU/ml bacteria to 1.25 to 20 W/V% of green tea extract or the PBS solution containing 25 to 400 micrograms/ml of (-) epigallocatechin gallate (EGCg), which is the main catechin ingredient of green tea leaf, and counted the number of live bacteria at various intervals. After 3 to 5 hours, no live bacteria were seen in 1.25 to 2.5 (regular drinking concentration) % green tea extract. In the high concentrations of 100 to 400 micrograms/ml EGCg the number of live bacteria decreased with time and after 24 hours no survivors were seen. In the low concentrations of 25 to 50 micrograms/ml EGCg, however, no change was observed in the number of live bacteria during 5 hours. After 24 hours the bacteria in 50 micrograms/ml were killed and the number of bacteria in 25 micrograms/ml decreased to one tenth of that at the start. To examine the anti-toxin activity, we mixed equal volumes of 2 ng/0.1 ml VT2 and 0.5 to 2 mg/0.1 ml catechin in vitro and incubated them at 37 degrees C for various times. Then we inoculated 0.2 ml of the mixture intraperitonealy to BALB/c mice. One mg of catechin inhibited by 100% the lethal toxicity of 2 ng of VT2 (LD 100) to mice. The inhibition of lethal toxicity of VT2 by catechin depended on the incubation time. The rate of inhibition was 0, 40 and 100% for 9, 12 and 18-24 hours incubation, respectively. These results suggest that catechin has not only bactericidal activity on EHEC O157:H7 but also anti-toxin activity on vero toxin.