Abstract

Chloroform and ethanol extracts of black cumin seeds (Nigella sativa) were analyzed for antibacterial activity against five food and water borne pathogens, namely, Staphylococcus aureus, Bacillus cereus, Vibrio cholerae, Klebsiella pneumoniae, Escherichia coli, and one food spoilage bacteria Bacillus subtilis, all of which were previously found to be resistant to different antibiotics. The antibacterial activities of the extracts were determined by disc diffusion and tube dilution methods. All the bacterial strains except E. coli and K. pneumoniae, showed sensitivity to the chloroform extract as well as the bacterial strains except the K. pneumoniae showed sensitivities to ethanol extract. The minimum inhibitory concentration (MIC) and minimum lethal concentration (MLC) of both extracts were also evaluated. Ethanol extract of black cumin was as found to be highly effective for B. subtilis (MIC value 375 µg/ml), followed by S. aureus (MIC value 1125 µg/ml). The highest concentration of extract was required for E. coli for complete inhibition of their growth. MIC value for E. coli was 3000 µg/ml. These results suggest that black cumin seeds may have potential antibacterial activity against multiple antibiotic-resistant bacteria.

Key words: Black cumin, multi-drug resistant bacteria, ethanol extract, chloroform extract.