S HEDAYAT<sup>1

1</sup>Unit of clinical microbiology,Department of infectious diseases,Barts and the London school of Medicine and Dentistry, Blizard institute ,Queen Mary University of London, London, UK ( United Kingdom)

Antibiotic properties of different types of tea against different microorganisms were detected whether the teas are able to inhibit growth of the microorganisms. At first, antibiotic properties of extract of different types of teas were investigated on different microorganisms staphylococcus aureus, staphylococcus epidermidis, streptococcus faecalis, E.coli, Pseudomonas aeruginosa, Listeria ivanovii, Acinetobacter, Klebsiella species by well method and BSAC method. In the second step, the disc diffusion sensitivity test was applied for MRSA and ESBL E.coli by BSAC method by measuring of zone sizes. The MRSA and ESBL E.coli were tested against all the tea hot extracts using two methods well cut in agar and paper disk dipped in the tea. Then synergy testing of MRSA and ESBL E.coli organisms was performed with the same antibiotics used for BSAC sensitivity test along with paper disc of hot extract of teas. Changes in zone size or shape were observed. Moreover, zone size of antibiotics and teas compared with second part. The results of testing of the all of the teas against the microorganisms showed zone of inhibition for Staph aureus and staph epidermidis with some tea types. There was no zone of inhibition for E.coli, Pseudomonas aeruginosa, Klebsiella species. These organisms are resistant to all of the teas. The results of testing the microorganisms MRSA and ESBL E.coli against all the hot tea extracts using well method and paper disc method showed that some teas were able to inhibit the growth of MRSA while ESBL E.coli was resistant to all of teas in both methods. There was no synergy between hot tea extracts and antibiotics used for BSAC sensitivity test for MRSA and ESBL E.coli. Tea extracts are not able to improve the effect of antibiotics on MRSA and ESBL E.coli. In this research, Gram-positive bacteria MRSA, Staph aureus and staph epidermidis are more sensitive than Gram-negative bacteria to antibiotic properties of tea extracts. The structure of the bacterial cell wall and the different affinities of the main catechin (EGCG) of tea with various cell wall components are responsible for the different susceptibilities of the observed antibacterial activity.