Abstract

A rapid and cost-effective approach to screening pathogens and evaluating potential antimicrobials is imperative to solve problem of antimicrobial resistance. The resazurin based broth microdilution and paper disc diffusion assays were used to evaluate the susceptibility pattern of a wild Escherichia coli to standard antibiotics, aqueous, ethanol, methanol, chloroform, n-hexane extracts of fifteen medicinal plants from Delta State, Nigeria. The phytochemical composition of medicinal plants’ extracts was analyzed with standard chemical methods. Regression analysis was used to establish the Minimum Inhibitory Concentrations (MIC) and Half Maximal inhibitory Concentrations (IC50) of the reference antibiotics and medicinal plant extracts, with the resazurin based broth microdilution method in a six-hour period. The percentage yield of extracts varied from 18.68±1.18% Aspilia africana (ethanol extract) to 1.62±0.19% of Psidium guajava (n-hexane extract). The predominant phytochemicals in the medicinal plant extracts were alkaloids, flavonoids, phenols, glycosides, and tannins. The IC50 of the dose-response curves correlated positively with MIC values of reference antibiotics (r = 0.97). The paper disc diffusion and resazurin-based microbroth dilution assays recorded eight and ten potent antimicrobial plant extracts .............................................................