Drug interaction studies of Ximenia americana and Pavetta crassipes methanol extract with standard antibiotics

Abstract

The therapeutic efficacy of single or multicomponent herbs is thought to reside in synergistic interactions between the bioactive constituents. The methanol extracts of X. americana and P. crassipes were  initially screened against Gram positive and negative organisms as well as against Mycobacterium  tuberculosis H37Rv but the antibacterial activities were not potent enough to warrant further explorations as stand-alone antibacterials. Using the agar diffusion method, standard antibiotics were screened for drug susceptibility against Staphylococcus aureus (ATCC 25823), Escherichia coli (ATCC 11560) and Pseudomonas aeruginosa (ATCC 10662). The antimicrobial activities were then screened against the same organisms in the presence of the extracts at a final concentration of 5 mg/ml in order to determine the influence on the inhibitory activities by measuring changes in the zone diameters. The study showed that the antibacterial interaction with P. crassipes extract was more prominent with the penicillins and tetracycline against S. aureus and P. aeruginosa while X. americana had prominent interaction with the same antibiotics in addition to  cotrimoxazole and the aminoglycosides, streptomycin and gentamicin. The interaction between the extracts and some of the antibiotics could be further explored for synergism especially with the Gram negative organisms.

Keywords: Drug interaction; Antibiotics; P. crassipes; X. Americana; S. aureus; E. coli; P. aeruginosa