Effect of the Combination of Stem Bark Extract of Parkia biglobosa (Jacq) Benth and Certain Antibiotics against Some Organisms of Medical Importance

Plant-derived compounds are known to exhibit a direct antibacterial activity and or an indirect activity as antibiotic resistance modifying compounds, and when combined with antibiotics, increased effectiveness may be observed. In this study, effort was directed towards combining the aqueous fraction of the methanol extract of the stem bark of Parkia biglobosa with some antibiotics to observe their combination effects on some organisms of medical importance. The minimum inhibitory concentration (MIC) of the extract and test antibiotics was determined using the checkerboard assay. Combination studies were carried out to ascertain the activities of the combinations against test organisms using the rate of kill assay and checkerboard assay. Results obtained confirmed interaction between the plant extract and the test antibiotics. It specifically confirmed synergistic interaction between Tetracycline, Erythromycin and Nalidixic acid respectively and the extract against Pseudomonas aeruginosa and Escherichia coli. Results obtained proved that in the search for alternative ways of combating bacterial infections, combination of plant extract with antibiotics could boost effectiveness and the aqueous fraction of the methanol extract of Parkia biglobosa is a possible candidate for this purpose against two of the tested organisms.