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Evidence-Based Complementary and Alternative Medicine
Volume 2014 (2014), Article ID 423751, 11 pages
Research Article

Influence of First-Line Antibiotics on the Antibacterial Activities of Acetone Stem Bark Extract of Acacia mearnsii De Wild. against Drug-Resistant Bacterial Isolates

Department of Nature Conservation, Mangosuthu University of Technology, P.O. Box 12363, Jacobs, KwaZulu-Natal, Durban 4026, South Africa

Received 28 March 2014; Accepted 12 June 2014; Published 1 July 2014

Academic Editor: Sandy van Vuuren

Copyright © 2014 Olufunmiso O. Olajuyigbe and Roger M. Coopoosamy. 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.


Background. This study was aimed at evaluating the antibacterial activity of the acetone extract of A. mearnsii and its interactions with antibiotics against some resistant bacterial strains. Methods. The antibacterial susceptibility testing was determined by agar diffusion and macrobroth dilution methods while the checkerboard method was used for the determination of synergy between the antibiotics and the extract. Results. The results showed that the susceptibility of the different bacterial isolates was concentration dependent for the extract and the different antibiotics. With the exception of S. marcescens, the inhibition zones of the extract produced by 20 mg/mL ranged between 18 and 32 mm. While metronidazole did not inhibit any of the bacterial isolates, all the antibiotics and their combinations, except for ciprofloxacin and its combination, did not inhibit Enterococcus faecalis. The antibacterial combinations were more of being antagonistic than of being synergistic in the agar diffusion assay. From the macrobroth dilution, the extract and the antibiotics exerted a varied degree of inhibitory effect on the test organisms. The MIC values of the acetone extract which are in mg/mL are lower than those of the different antibiotics which are in g/mL. From the checkerboard assay, the antibacterial combinations showed varied degrees of interactions including synergism, additive, indifference, and antagonism interactions. While antagonistic and additive interactions were 14.44%, indifference interaction was 22.22% and synergistic interaction was 37.78% of the antibacterial combinations against the test isolates. While the additivity/indifference interactions indicated no interactions, the antagonistic interaction may be considered as a negative interaction that could result in toxicity and suboptimal bioactivity. Conclusion. The synergistic effects of the herbal-drug combinations may be harnessed for the discovery and development of more rational evidence-based drug combinations with optimized efficiency in the prevention of multidrug resistance and therapy of multifactorial diseases.