Antibacterial Activity of Nigella sativa extract against selected bacterial clinical isolates from Khartoum State

Abstract

An alarming increase in bacterial strains resistant to existing antibacterial agents demands a renewed effort to seek agents effective against pathogenic bacteria resistant to antibacterials. The aim of this study was to study the antibacterial activity of different concentrations of petroleum ether and methanol extracts of medicinal plant Nigella sativa (seeds) using cup-plate agar diffusion method on slected clinical isolates of bacteria. The study was conducted in Khartoum state, Sudan, during the period from June to November 2015. One hundred forty four samples were collected form urine, wound and stool, 103/144 (72%) showed bacterial growth, from which nine types of pathogenic bacteria were isolated and identified using Gram stain, biochemical reactions and tested for their susceptibility to a number of antibiotics. Those were resistant to three or more antibiotics were tested for their sensitivity to Nigella sativa extracts. The tested isolates included, Klebsiella pneumoniae 32(31%), Escherichia coli 22(21%), Staphylococcus aureus 21(20%), Proteus mirabilis 11(11%) and Pseudomonas aeruginosa 9(9%). The petroleum ether and methanol extract of Nigella sativa were screened for their antibacterial activity against standard and clinical isolates. Petroleum ether extract of Nigella sativa showed pronounced dose dependant antibacterial activity on standard strains and clinical isolates, while methanolic extract showed no activity. Petroleum ether extract of Nigella sativa showed antibacterial activity against standard and clinical isolates of S.aureus, K.pneumoniae and E.coli, while only standard strains of P. mirabilis and Ps. aeruginosa were sensitive to it.