B-241. Effects of Tea Extracts on the Formation of Biofilm and Production of Enterotoxins by Staphylococcus aureus

J. Cui1,2, S. Jin1,2, M. Yun1, P. Ryu1;
1Res. Inst. of Vibrio Infection and Genome Res. Ctr. for Enteropathogenic Bacteria,Chonnam Univ. Med. Sch., Gwangju, REPUBLIC OF KOREA, 2Ctr. for Biomedical Human Resources, Gwangju, REPUBLIC OF KOREA.

In this study, it was investigated that the effects of tea extracts and six catechin derivatives on the formation of biofilm and production of enterotoxin by Staphylococcus aureus aggregating atopic dermatitis (AD). Minimum inhibitory concentration (MIC) (1.25-2.5%) of tea extracts to strains was 2-4 times higher than minimum bactericidal concentration (2.5-10%), and MIC of six catechin derivatives were all more than 1,000 µl/ml except the group producing enterotoxin C and MIC (250-500 µl/ml) of epigallocatechin (EGC) was lower than the others. The formation of biofilm caused by the strains which were cultured in the media mixed with 0.25% (W/V) tea extracts was significantly inhibited. We inoculated the bacteria into the Congo red agar with tea extracts, then the results showed that the group treated with 0.06% tea extracts presented the color of wine, however that treated with 0.13% tea extracts presented red, the production of glycocalyx was inhibited and the size of colonies looked like smaller than the control. In the strains treated with catechin derivatives, the formation of biofilm caused by the EGCG-treated strain was inhibited most markedly at the over concentration of 8 µl/ml, furthermore the GCG-treated strain no less than 8-63 µl/ml and EGC no less than 16-250 µl/ml. Tea extracts had an inhibitory effect on the production of staphylococcal enterotoxin A, C and D, and especially the production of staphylococcal enterotoxin A and C were inhibited in the group treated with 0.063% tea extracts. The inhibitory effects on the production of staphylococcal enterotoxin were also observed in the EGC and EGCG-treated groups, and that EGCG had a significant effect even at the 63 µl/ml of concentration. From the above results it was speculated the tea extracts were a good candidate to cure AD by inhibiting the production of staphylococcal enterotoxin and inhibiting the production of mucous lay to block the formation of biofilm.