Potential in vitro inhibitory effects of Moringa oleifera leaf extracts on extended-spectrum β-lactamase-producing bacteria

Extended-spectrum β-lactamase (ESβL) enzymes are produced by certain bacteria as a mechanism of resistance to β-lactam and extended-spectrumβ-lactam antibiotics. Previous investigations have confirmed that M. oleifera contains several bioactive compounds. This study aimed at evaluating the in vitro antibacterial effects of ethanolic and methanolic leaf extracts of M. oleifera on extended-spectrum β-lactamase producing bacteria. The leaf extracts of the plant were prepared, screened for bioactive compounds and evaluated for in vitro inhibitory effects against the ESβL-producing bacteria using agar well diffusion method. Different phytochemicals were detected from the extracts. Both methanolic and ethanolic leaf extracts showed a high inhibitory activity, which increased with an increase in concentration, from lowest to highest based on the zones of growth inhibition produced. Amongst the test organisms, Klebsiella pneumoniae was the most sensitive isolate to methanolic extract at 200, 100, 50 and 25mg/mL followed by Escherichia coli, and then Proteus mirabilis. However, in terms of the ethanolic extract, using the same concentrations as those of methanol extracts, E. coli was found to be the most sensitive isolate followed by K. pneumoniae and then P. mirabilis.