Synergistic antimicrobial activity of tea & antibiotics.

Tea leaves are known for its antibacterial activity against many microorganisms. In this study we attempted to describe the synergistic antimicrobial activity of tea and antibiotics against enteropathogens. Antimicrobial activity of boiled water tea extract and organic solvent extract were studied against Salmonella typhimurium 1402/84, S. typhi, S. typhi Ty2a, Shigella dysenteriae, Yersinia enterocolitica C770, and Escherichia coli (EPEC P2 1265) determining minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and death rate kinetics at MBC of tea extract in presence of subinhibitory concentration of antibiotic. Both green tea or black tea extracts effectively inhibited the growth of S. typhimurium 1402/84, S. typhi, S. typhi Ty2a, S. dysenteriae, Y. enterocolitica C770, and E.coli (EPEC P2 1265). However, the growth inhibitory concentration of tea extract was lower for green tea as compared to black tea extract. Antimicrobial activity of green tea tea methanol: water extract tea was better as compared to boiled water tea extract of green tea. Based on death rate kinetics results, S.typhi Ty2a appeared to be highly sensitive and Y. enterocolitica C770 the most resistant. Chloramphenicol and tea extract in combination inhibited the growth of S.dysenteriae at 2.5 microg/ml chloramphenicol (MIC 5 microg/ml) and 5.094 mg/ml black tea extract (MIC 9.089 mg/ml). Tea extract showed synergistic activity with chloramphenicol and other antibiotics like gentamycin, methicillin and nalidixic acid against test strains.