Comparative evaluation of antibacterial efficacy of plants traditionally used as antidiarrheal against enteropathogenic Escherichia coli

Abstract

The study was conducted to investigate the antibacterial efficacy against enteropathogenic E. coli of plants commonly used to treat calf-diarrhoea. Methanolic extracts of six plants (Aegle marmelos, Curcuma longa, Dalbergia sissoo, Mangifera indica, Psidium guajava and Punica granatum) were screened for their antibacterial property against enteropathogenic E. coli by standard disc diffusion method. Minimum inhibitory concentration (MIC) and of the extract exhibiting highest antibacterial activity was estimated by broth dilution method and minimum bactericidal concentration (MBC) was measured by streaking the contents of MIC tubes on nutrient agar plates. Among the six extracts tested, only extracts of Curcuma longa, Psidium guajava and Punica granatum exhibited antibacterial activity against E. coli. Out of these three, Punica granatum extract was found to be most effective with a mean inhibition zone of 14.67±0.577 mm followed by Psidium guajava (9.67±0.577 mm) and Curcuma longa (8.67±0.577 mm), produced by the disc containing 8.00 mg of respective extract. Minimum inhibitory concentration and minimum bactericidal concentration of the Punica granatum extract were estimated to be 02.00 mg/mL and 03.00 mg/mL respectively. These findings suggest that methanolic extracts of Curcuma longa, Psidium guajava and Punica granatum possess antibacterial activity against enteropathogenic E.coli