Antibacterial activities of five plants against some medically significant human bacteria

THE ANTIBACTERIAL ACTIVITIES OF THE crude extracts of the roots and stems of Datura stramonium, Zanthoxylum davyi, Securidaca longipedunculata, Wrightia natalensis and Piper capense, with and without autoclaving, were determined against Gram-negative and Gram-positive bacteria of medical importance. The disk diffusion, hole-plate diffusion and agar dilution methods were employed for antibacterial testing. Results revealed marked antibacterial activities of the extracts of the roots and stems of D. stramonium against most of the test organisms with zone diameters of inhibition of growth ranging from 6-20 mm. Pseudomonas aeruginosa and Proteus mirabilis/vulgaris were observed to be completely resistant to the extracts of D. stramonium. Zanthoxylum davyi showed pronounced antibacterial activities against E. coli, Shigella species, Salmonella typhi and Streptococcus pyogenes, whereas strains of Staphylococcus aureus were completely resistant. Extracts of the roots and stems of S. longipedunculata were only markedly active against S. pyogenes and Shigella whereas S. aureus, E. coli and S. typhi demonstrated complete resistance. Root extracts of W. natalensis and P. capense were strongly active against S. aureus, S. pyogenes and C. xerosis, but had no effect on Haemophilus influenzae and H. parainfluenzae. We observed no significant differences between the activity of autoclaved and non-autoclaved samples of the respective extracts.