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BioMed Research International
Volume 2013 (2013), Article ID 927323, 4 pages
Research Article

A Simple Assay to Screen Antimicrobial Compounds Potentiating the Activity of Current Antibiotics

1Department of Biological and Biomedical Sciences, Aga Khan University, Stadium Road, Karachi 74800, Pakistan
2Department of Microbiology, University of Karachi, Karachi 75270, Pakistan

Received 9 April 2013; Revised 29 May 2013; Accepted 4 June 2013

Academic Editor: Kuo-Chen Chou

Copyright © 2013 Junaid Iqbal et al. 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.


Antibiotic resistance continues to pose a significant problem in the management of bacterial infections, despite advances in antimicrobial chemotherapy and supportive care. Here, we suggest a simple, inexpensive, and easy-to-perform assay to screen antimicrobial compounds from natural products or synthetic chemical libraries for their potential to work in tandem with the available antibiotics against multiple drug-resistant bacteria. The aqueous extract of Juglans regia tree bark was tested against representative multiple drug-resistant bacteria in the aforementioned assay to determine whether it potentiates the activity of selected antibiotics. The aqueous extract of J. regia bark was added to Mueller-Hinton agar, followed by a lawn of multiple drug-resistant bacteria, Salmonella typhi or enteropathogenic E. coli. Next, filter paper discs impregnated with different classes of antibiotics were placed on the agar surface. Bacteria incubated with extract or antibiotics alone were used as controls. The results showed a significant increase (>30%) in the zone of inhibition around the aztreonam, cefuroxime, and ampicillin discs compared with bacteria incubated with the antibiotics/extract alone. In conclusion, our assay is able to detect either synergistic or additive action of J. regia extract against multiple drug-resistant bacteria when tested with a range of antibiotics.