Inhibitory Effects of Selected Thai Spices and Medicinal Plants on Escherichia coli O157 : H 7 and Yersinia enterocolitica

Abstract

The effects of spices and medicinal plants were tested for their inhibitory effects on newly foodborne pathogens namely Escherichia coli O157 : H 7 and Yersinia enterocolitica by the well assay technique. Crude extracts of cloves (Eugenia caryophyllata Thunb.) and cinnamon (Cinamonum zeylanicum Nees.) revealed high antibacterial activity on both organisms. The betle leaf (Piper betle) showed the highest activity on E. coli O157 : H 7, whereas the pomegranate rind (Punica granatum Linn.) exhibited the highest antibacterial action on Y. enterocolitica. The effects of pH and temperature on antibacterial activity of plant extracts were explored. The antibacterial activity of plant extracts on the test organisms at selected pH values indicated that it was more active at low pH than at high pH. At low temperatures (4 and 10°C) the plant extracts have less activity than at high temperatures (25, 35 and 45°C).