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Int. J. Mol. Sci. 2012, 13(7), 8915-8932; doi:10.3390/ijms13078915
Article

Synergistic Interactions of Methanolic Extract of Acacia mearnsii De Wild. with Antibiotics against Bacteria of Clinical Relevance

 and *
Phytomedicine Research Centre, Department of Botany, University of Fort Hare, Alice 5700, South Africa
* Author to whom correspondence should be addressed.
Received: 27 March 2012 / Revised: 27 June 2012 / Accepted: 10 July 2012 / Published: 17 July 2012
(This article belongs to the Section Bioactives and Nutraceuticals)
View Full-Text   |   Download PDF [148 KB, 19 June 2014; original version 19 June 2014]

Abstract

With the emergence of multidrug-resistant organisms, combining medicinal plants with synthetic or orthodox medicines against resistant bacteria becomes necessary. In this study, interactions between methanolic extract of Acacia mearnsii and eight antibiotics were investigated by agar diffusion and checkerboard assays. The minimum inhibitory concentrations (MICs) of all the antibiotics ranged between 0.020 and 500 µg/mL while that of the crude extract varied between 0.156 and 1.25 mg/mL. The agar diffusion assay showed that extract-kanamycin combination had zones of inhibition ≥20 ± 1.0 mm in all the bacteria tested (100%), followed by extract-chloramphenicol (90%) > extract-ciprofloxacin = extract-tetracycline (70%) > extract-amoxicillin (60%) > extract-nalidixic acid (50%) > extract-erythromycin (40%) > extract-metronidazole (20%). The checkerboard showed synergistic interaction (61.25%), additivity/indifference (23.75%) and antagonistic (15%) effects. The synergistic interaction was most expressed by combining the extract with tetracycline, metronidazole, amoxicillin, ciprofloxacin, chloramphenicol and nalidixic acid against E. coli (ATCC 25922), erythromycin, metronidazole, amoxicillin, chloramphenicol and kanamycin against S. aureus (ATCC 6538), erythromycin, tetracycline, amoxicillin, nalidixic acid and chloramphenicol against B. subtilis KZN, erythromycin, metronidazole and amoxicillin against E. faecalis KZN, erythromycin, tetracycline, nalidixic acid and chloramphenicol against K. pneumoniae (ATCC 10031), erythromycin, tetracycline, metronidazole and chloramphenicol against P. vulgaris (ATCC 6830), erythromycin, tetracycline, amoxicillin and chloramphenicol against S. sonnei (ATCC 29930), metronidazole, amoxicillin and chloramphenicol against E. faecalis (ATCC 29212) and ciprofloxacin and chloramphenicol against Proteus vulgaris KZN. The synergistic interactions indicated that the bactericidal potentials of the antibacterial agents were improved and combining natural products with antibiotic could be potential sources for resistance-modifying agents useful against infectious multi-drug resistant bacteria.
Keywords: Acacia mearnsii; checkerboard assay; drug-herbal interaction; multi-drug resistance; synergistic effects Acacia mearnsii; checkerboard assay; drug-herbal interaction; multi-drug resistance; synergistic effects
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Olajuyigbe, O.O.; Afolayan, A.J. Synergistic Interactions of Methanolic Extract of Acacia mearnsii De Wild. with Antibiotics against Bacteria of Clinical Relevance. Int. J. Mol. Sci. 2012, 13, 8915-8932.

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