Purpose: Concurrent use of orthodox and herbal medicines is likely to precipitate an overall effect which may or may not be beneficial to the patient. The objective of this study was to evaluate the antimicrobial interaction between the methanol extract of Garcinia kola seed (GKS) which is chewed habitually as a masticatory in many rural communities in Africa and gatifloxacin (GAT), a fourth generation fluoroquinolone.
Method: The antimicrobial interaction between these two agents was evaluated by a modification of the checkerboard technique using Bacillus subtilis and Staphylococcus aureus as the test organisms.
Result: Results obtained showed that the minimum inhibitory concentration (MIC) of gatifloxacin against both organisms was 1.0 µg/ml while the MICs of the G. kola seed extract were evaluated to be 1.562 mg/ml and 3.125 mg/ml respectively against B. subtilis and S. aureus. Upon combination, synergism was manifested serially against B. subtilis in ratios of 9(GAT):1(GKS) down to 6(GAT) :4(GKS) after which additivity, indifference and antagonism, in that order, were manifested as the ratio of GKS increased in the combination. Against S. aureus, the combined interaction showed a somewhat irregular pattern of effect, including synergism at GAT:GKS ratios of 9:1, 2:8 and 1:9 , antagonism at ratios of 8:2, 5:5 and 4:6 and indifference at GAT:GKS ratios of 7:3, 6:4 and 3:7.
Conclusion: The results from this study suggest that the effect of combination of the methanol extract of GKS with gatifloxacin was dependent not only on the ratio of combination but also on the test organism employed for the evaluation. Overall, the combined antimicrobial effect of the interaction between GKS and gatifloxacin was predominantly synergistic against B.subtilis.
Keywords Garcinia kola seed, antibacterial interaction, checkerboard technique, Bacillus subtilis, Staphylococcus aureus, gatifloxacin