Antibacterial activities of three medicinal plants against some gastro-intestinal microorganisms

Abstract

The in vitro antibacterial activity of aqueous (cold and hot water extract) and ethanolic leaf extracts of Bambusa vulgaris, Erigeron floribundus, and Fluerya aestuans were evaluated against clinical isolates of Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Salmonella typhi, and Shigella
dysentriae using agar well diffusion and broth dilution techniques respectively. Tetracycline was used as positive control antibiotics. The antibacterial assay showed that the three plants significantly inhibited all the test organisms at varying degrees. The ethanolic and hot aqueous
extracts displayed greater antimicrobial activity than the cold extracts. The diameters of zones of inhibition of the plant extracts ranged from 7.8 - 15.5 mm for the ethanol extracts, 7.0 -12.0 mm and 5.0 - 8.5 mm for hot and cold aqueous extracts respectively depending on the test organisms.
Their MIC values ranged from 31.25 – 125 mg/ml. The activities of the extracts were significantly lower (p<0.05) than those of the tetracycline for which MIC values ranged from 3.91 - 7.81mg/ml. The antimicrobial activity of the standard antibiotics used was not affected (p<0.05) by the plant
extracts when combined and tested against the isolates. The activities observed could be due to the presence of some secondary metabolites like, steroids, alkaloids, tannins, saponins, phenols, glycosides and flavonoids, which were detected in the extracts. This study therefore, established a good support for the use of these plants in traditional medicines.

Keywords: Bambusa vulgaris, Erigeron floribundus, Fluerya aestuans, medicinal plants