[Bactericidal and anti-toxin activities of catechin on enterohemorrhagic Escherichia coli].
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.
Okubo
S
S
Department of Microbiology and Immunology, Showa University School of Medicine.
Sasaki
T
T
Hara
Y
Y
Mori
F
F
Shimamura
T
T
D000818:Animals; D001252:Astringents / Q000494:pharmacology*; D001427:Bacterial Toxins / Q000037:antagonists & inhibitors*; D002392:Catechin / Q000494:pharmacology* / Q000031:analogs & derivatives; D003603:Cytotoxins / Q000037:antagonists & inhibitors*; D004768:Enterotoxins / Q000037:antagonists & inhibitors*; D019453:Escherichia coli O157 / Q000187:drug effects*; D005419:Flavonoids / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D022622:Shiga Toxin 1; D013662:Tea
D001252:Astringents; D001427:Bacterial Toxins; D003603:Cytotoxins; D004768:Enterotoxins; D005419:Flavonoids; D022622:Shiga Toxin 1; D013662:Tea; D002392:Catechin; C057580:gallocatechol