Evaluation of the combined antimicrobial activity of the leaf extract of phyllantus muellerianus with ciprofloxacin

Abstract

Background: Infectious diseases caused by multi-resistant microbial strains are on the increase. Fighting these diseases with natural products may be more efficacious. The aim of this study was to investigate the in vitro antimicrobial activity of methanol leaf extract and chromatographic fractions of the extract of Phyllanthus muellerianus (Kuntze) Excell against Klebsiella spp., Enterococcus faecalis, Pseudomonas earuginosa, Proteus mirabilis, Escherichia coli, Salmonella spp. and Candida albicans. The combined effect of the extract or its fractions with ciprofloxacin was also tested. Methods: The antimicrobial properties of the methanol extract of P. muellerianus and its fractions were determined in vitro using the agar diffusion method. Agar diffusion Checkerboard method and Overlay Inoculum susceptibility disc method were used to study the interaction of the extract or fraction with ciprofloxacin. The extract was subjected to phytochemical analysis for identification of constituents using standard procedures. The minimum inhibitory concentration (MIC) data obtained from the antimicrobial studies were analyzed for significant difference at p<0.05 using one way analysis of variance (ANOVA). Results: While n-hexane and methylene chloride fractions showed no activity against the test microorganisms, methanol crude extract and methanol fraction of the extract revealed a good concentration dependent antibacterial activity against P. earuginosa, P. mirabilis and E. faecalis. Combinations of the extract and ciprofloxacin produced antagonistic effect against P. mirabilis and E. faecalis while a synergistic effect was obtained against P. aeruginosa. The results of the phytochemical screening showed that the extract and the fractions contain glycosides, flavoniods, saponins, alkaloids. Conclusion: The methanol leaf extract of Phyllanthus muellerianus possess antibacterial activity against P. earuginosa, P. mirabilis and E. faecalis and could possibly be used in combination with ciprofloxacin to treat infections caused by P. aeruginosa.