Comparative Evaluation of the Antibacterial Effects of Nigella sativa and Moringa oleifera on some Clinical Bacteria Isolates

Aim: In this study, the antibacterial effect of the n-hexane, methanol, and ethanol extracts of two traditional medicinal plants, Nigella sativa and Moringa oleifera was carried out to comparatively assess the antibacterial efficacy of these plants against some selected multi-drug resistant diarrheagenic bacterial isolates such as Escherichia coli, Salmonella typhi, Shigella spp, Enterobacter aerogenes, Klebsiella pneumonia, and Pseudomonas aeruginosa.

Methodology: The inhibitory effects of extracts were assessed using disk diffusion method at six different concentrations i.e. 12.5 mg/ml, 25 mg/ml, 50 mg/ml, 100 mg/ml, 200 mg/ml, and 400 mg/ml. The minimum inhibitory concentrations and minimum bactericidal concentrations of the plant seed extracts were determined by the micro-broth dilution technique. Synergism and antagonism studies were similarly done to determine the combined effects of both N. sativa and M. oleifera seed oil. Further, resistant bacteria were subjected to sodium dodecyl sulphate treatment for plasmid curing and continued with the antibiotic susceptibility test.

Results: The oil extracts of N. sativa were found to be more effective than that of M. oleifera (at MIC and MCC of 50 mg/ml and 100 mg/ml respectively). It was observed that the plasmids were cured in all the E. coli isolates. Among the pathogens, E. coli was highly susceptible to both seed oils.

Conclusion: Higher antibacterial activity was observed when the extracts were used in combination, showing a strong synergistic effect against all the pathogens tested.