Abstract

The antimicrobial activity of stem bark acetone extract of Erythrina caffra Thunb. against medically important pathogens was evaluated by determining the inhibition zones and the minimum inhibitory concentrations (MICs) of the extract. The result showed that the extract had good antimicrobial activity against the tested bacterial and fungal isolates with the increases in the inhibition zones being concentration dependent. The degree of the antibacterial activity indicated that the minimum inhibitory concentration (MIC) values ranged between 0.0195 and 1.25 mg/ml while the minimum bactericidal concentrations (MBC) ranged between 0.0391 and 1.25 mg/ml for the extract. The extract was less potent than the standard antibiotic, ciprofloxacin, having MIC values of (0.0195 to 0.625 µg/ml). For the fungal isolates, the MIC and minimum fungicidal concentration (MFC) values ranged between0.625 and 20 mg/ml. Though the results showed that the bacteria were more susceptible to the extract than the fungi, the extract inhibited Gram-negative bacteria more than the Gram-positive bacteria at low concentrations. This study shows a broad spectrum and great therapeutic potential of the plant with the ability to attract significant scientific attention.

Key words: Antimicrobial activity, broad spectrum, crude extract, fungicidal concentration, inhibitory effects, minimum inhibitory concentration (MIC) test.