ANTIBACTERIAL ACTIVITY OF CRUDE ETHANOLIC EXTRACTS AND ESSENTIAL OILS OF SPICES AGAINST SALMONELLAE AND OTHER ENTEROBACTERIA

Crude ethanolic extracts and essential oils of 14 spices including cardamom, cinnamon, clove, coriander, cumin, garlic, ginger, holy basil, kaffir lime leaves and peels, lemongrass, mace, nutmeg, black and white pepper, and turmeric were examined for their antibacterial activity against 20 serotypes of Salmonella and 5 species of other enterobacteria using disk diffusion method as preliminary screening. Of these, 9 crude ethanolic extracts and 11 essential oils were selected to determine the minimum inhibitory concentrations (MICs) using microbroth dilution test. Among all ethanolic extracts, clove extract had the most inhibitory effect on the growth of all bacterial strains tested. Oils of clove and kaffir lime peels exhibited greater antibacterial activity against all tested strains, compared to other spice oils. The oils of cardamom, coriander, and cumin were also potent inhibitors of bacterial growth, showing the lowest MIC of 4.2 μl/ml to most bacterial strains tested. Both oil and ethanolic extract of kaffir lime peels showed greater antibacterial action, compared to the extracts of kaffir lime leaves. In general, inhibitory activity of spice oils was greater than that of their own ethanolic extracts. Of all serotypes of Salmonella tested, Salmonella Typhimurium (non-DT104 strain) is the most susceptible strain to both forms of spice extracts. On the other hand, Salmonella Derby and Salmonella Rissen were the most resistant strains to the extracts, followed by Salmonella Agona and Salmonella Typhimurium DT104. Escherichia coli was more susceptible to most of the spice oils than other non-salmonellae strains tested.