Abstract

The inevitable development of drug resistance among bacterial pathogens prompted the search for alternative therapeutic methods. The combination therapy of plant antimicrobial compounds with antibiotics seems to be promising. The present study focuses on the synergistic effect of various extracts of Syzygium aromaticum (Linn.) in combination with ampicillin and tetracycline. Preliminary antibacterial investigations were carried out using extracts prepared from dried clove buds using four different solvents of increasing polarities (chloroform, methanol, ethanol and water). The antibacterial activity against different bacterial strains was analysed by agar well diffusion assay, determination of Minimum Bactericidal Concentration and time kill assay. Checkerboard assay and time kill assay of combinations of clove extract with the antibiotics was performed to demonstrate synergistic interactive effects of the drugs. The methanolic extract of clove was subjected to qualitative phytochemical screening for identification of various classes of active chemical constituents such as phenols, flavonoids, saponins, terpenoids, glycosides and alkaloids. Methanolic extract was also subjected to phytochemical compound analysis through RP-HPLC profiling. Clove (methanol) extract enhanced the antimicrobial activity of both ampicillin and tetracycline against Staphylococcus aureus, Methicillin resistant Staphylococcus aureus and Pseudomonas aeruginosa. Clove (methanol)-tetracycline combination proved to be the most effective combination against the MRSA strain used in the present study. The results suggest that extracts of Syzygium aromaticum (Linn.) could be employed to enhance the antibacterial activity of various antibiotic formulations.