Evaluation of the Antibacterial Activity of Gongronema latifolium and Costus afer Leaf Extracts on E. coli (ATCC 29455) and S. aureus (ATCC 25923)

Abstract

Man’s use of medicinal plants in treating illnesses is as old as human existence and many plants have been used for this purpose because of their phytochemical constituents that prove many times to be antimicrobial. The antibacterial activity of the leaf extract of Gongronema latifolium and Costus afer on Staphylococcus aureus (ATCC 25923) and Escherichia coli (ATCC 25923) was investigated using standard microbiological procedures of sub-culturing, identity confirmation, water and ethanol extraction of leaves and sensitivity testing via agar well diffusion method. Results revealed that S. aureus and E. coli were both inhibited by the aqueous extract of C. afer with zone diameter of 16 mm and 15 mm respectively as well as the ethanolic extract of C. afer with diameter of 18mm and 15 mm respectively. However, aqueous and ethanolic extracts of G. latifolium proved ineffective against the strains of E. coli and S. aureus used in this study. Results of minimum inhibitory concentration revealed MIC of the aqueous extract of C. afer on E. coli and S. aureus to be 50 mgml-1 and 25 mgml-1 respectively while that of the ethanolic extracts of C. afer was 12.5 mgml-1 and 6.25 mgml-1 for E. coli and S. aureus respectively. Comparatively E. coli showed high sensitivity to Ciprofloxacin, Gentamycin and Septrin with zones of inhibition of 37, 32 and 24 respectively and resistant to Ampicillin, Erythromycin and Tetracycline with zones of inhibition of 6, 0 and 0 respectively. S. aureus on the other hand proved sensitive to Ciprofloxacin, Erythromycin, Gentamycin and Tetracycline with zones of inhibition of 35, 28, 29 and 34 respectively and resistant to Ampicillin and Septrin with zones of inhibition of o respectively. This study has revealed that some positive effect can be achieved against S. aureus and E. coli infections using C. afer at good concentrations. Better results could also be achieved using ethanol as extracting medium with instead of water as is common practice.