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.