Lantana camara enhances antibacterial potency of antibiotics and exerts synergistic inhibitory effect against pathogenic bacterial species

Abstract

The present study aims at evaluating the potentiating ability of Lantana camara leaves and flower extracts in enhancing the antibacterial efficacy of antibiotics against pathogenic bacterial species. Methanolic extracts of L. camara leaves and flowers (pink turn yellow) were prepared by the solvent extraction method. The leaves and flower extracts alone and their combination with five different antibiotics; Ciprofloxacin, Streptomycin, Tetracycline, Nalidixic acid and Norfloxacin were assessed for their synergistic antibacterial potential against Escherichia coli MTCC 1698, Staphylococcus aureus MTCC 3160, Enterobacter fecalis MTCC 439, Proteus vulgaris MTCC 1771 and Salmonella typhi MTCC 733, using an agar disc diffusion method and checkerboard antibacterial susceptibility assay. The minimum inhibitory concentration of Lantana extracts and antibiotics was assessed using broth micro-dilution assay. In agar disc diffusion assay, the combination of the flower extract and streptomycin depicted 5.26–25% increase in ZOI against S. aureus, and S. typhi. In the checkerboard antibacterial assay, the Ciprofloxacin and flower extract showed a synergistic inhibitory effect against E. coli, S. aureus, E. fecalis, P. vulgaris and S. typhi (FIC index, ranging from 0.39 to 0.14), while the combination of leaves extract and streptomycin exerted additive effect against S. typhi and E. coli (FICI = 0.46 and 0.48 respectively). The MICs of Lantana leaves and flower extracts against the test bacterial strains were depicted between 31.25 μg/ml and 250 µg/ml. L. camara leaves and flower extracts enhance the antibacterial potency of antibiotics and their synergistic combination could emerge as a novel therapeutics against pathogenic bacterial species.