Comparative Antibacterial Analysis and Synergistic Potency of the Leaf Extracts of Ocimum gratissimum Linn. and Gongronema latifolium Benth. on Some Enteric Bacterial Isolates

Abstract

The research was undertaken to investigate the comparative phytochemical and in-vitro antibacterial activity of the single and combined strengths of the leaf extracts of Ocimum gratissimum Linn and Gongronema latifolium Benth. on some enteric bacterial isolates. The sensitivity test and minimum inhibitory concentration (MIC) were carried out using a modified agar-well diffusion method.  The enteric bacterial isolates tested included Escherichia coli, Shigella dysenteriae, Salmonella Typhi and Enterobacter aerogenes.  Standard methods were applied to obtain the ethanol and aqueous leaf extracts. The ethanol extracts of O. gratissimum and G. latifolium produced highly significant inhibitory activity against all the enteric bacterial isolates tested.  Comparatively, the ethanol plant extracts were more potent than the commercially available drug, Ciprofloxacin and the aqueous plant extracts. The isolates were sensitive at a minimum inhibitory concentration of 1.25 mg/ml for the ethanol extract but varied from 2.5 mg/ml - 5.0mg/ml in the aqueous extract.  It was also observed that the synergistic antibacterial effect of the medicinal plant extracts was greater than the singular antibacterial effect of the individual plant extracts in both the ethanol and aqueous extracts. The potency of the individual extracts and the combined effect may be due to the presence of flavonoids, alkaloids, phenols, tannins and saponins in the leaves of the plants.  This study partly validates the use of the plant extracts in the treatment of disease caused by the enteric bacterial isolates by multiple traditional medicine practitioners in Nigeria, however, strict adherence to dosage is recommended.  The leaf extract is a potential source of the new drug if the components are purified and enhanced for treating infections caused by these enteric pathogens.