The aim of this study was to evaluate the in vitro antimicrobial interaction between the ethanol leaf extract of Moringa oleifera (MO), which is used in Nigeria as a dietary supplement, and ciprofloxacin (Cp), a flouroquinolone antibiotic. Preliminary antimicrobial screening of the ethanol extract of M. oleifera and ciprofloxacin was determined in vitro using the agar dilution method. The antimicrobial interaction between these agents was evaluated by the Checkerboard technique using Staphylococcus aureus and Pseudomonas aeruginosa as test organisms. The minimum inhibitory concentration (MIC) values of the extract against S. aureus and P. aeruginosa were 25.0 and 50.0 mg/mL, respectively, while that of ciprofloxacin were 0.00062 and 0.0005 mg/mL against S. aureus and P. aeruginosa, respectively. The antibacterial interaction studies indicated that the combinations predominantly showed additive effects at Cp : MO ratios of 8:2, 7:3, 6:4 and 5:5 against S. aureus while Cp : MO ratios of 9:1, 8:2, 7:3 and 6:4 yielded predominantly synergistic effect against P. aeruginosa. Other combination ratios had no MIC, hence no observed effect. This study has demonstrated that the ethanol leaf extract of M. oleifera possesses potent antibacterial effect against S. aureus and P. aeruginosa. Overall, the combined antimicrobial effect of the interaction between the extract and ciprofloxacin was predominantly synergistic against P. aeruginosa. Regarding its relevance, this study has provided a preliminary evidence of some kind of antibacterial interaction between ethanol extract of M. oleifera leaf and ciprofloxacin against P. aeruginosa and has established that the use of M. oleifera concurrently with ciprofloxacin would yield greater effectiveness in the treatment of infections in which P. aeruginosa is implicated than when either ciprofloxacin or the extract is used alone.
Key words: Moringa oleifera leaf, antibacterial interaction, checkerboard technique, Staphylococcus aureus, Pseudomonas aeruginosa, ciprofloxacin
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