Antimicrobial activity of aqueous extract, methanolic extract and oil of nigella sativa (kalonji) against gram positives and gram negatives clinical isolates

Nigella sativa seed (Black cumin seed; Kalonji) was used since many years as medicinal product for the treatment of many infections. In the present study antibacterial effect of aqueous extract of seeds was studied against few of clinical isolates including both gram positive and gram negative species. Results were also compared with standard drugs. Most of the drugs were found to be non effective against isolates. Interestingly, during the recent study all isolates were resistant to oxacillin. Zones of inhibition were evaluated by disc diffusion and well diffusion method in all three preparation of Nigella sativa. Minimum inhibitory concentration was also determined by broth dilution method (aqueous extract) and agar dilution method (methanolic extract and Kalonji oil). Miles and Misra also performed and Log of cfu/ml calculated in aqueous preparation. Streptococcus pyogene found to be more sensitive to both aqueous and methanolic extract while among gram negatives Pseudomonas aeruginosa given larger zones of inhibition in the presence of methanolic extract, even in comparison of all gram positives. Killing time and growth curve of Staphylococcus aureus revealed that aqueous extract have bacteriostatic rather bactericidal activity while methanolic extract and oil given bactericidal effect against few isolates but Kalonji oil found to be more effective as it required least concentration to kill the organisms.