Synergistic effect of ethanolic extract of propolis and antibiotics on the growth of staphylococcus aureus.

Ethanolic extract of propolis (EEP), known to possess marked antibacterial activity, was incubated with 8 different common antibiotics in culture medium containing a fixed amount of a standard strain of Staphylococcus aureus. The antibiotic compounds used were: penicillin G, doxycycline, streptomycin, cloxacillin, chloramphenicol, cefradine, ampicillin and polymyxin B. They were used in varying levels, ranging between 0.000005-125.0 micrograms/ml or units, resp. Firstly, their minimal inhibitory concentrations were established in the absence of EEP, than EEP was added in concentrations up to 600 micrograms/ml. EEP had a marked synergistic effect on the antibacterial activity of streptomycin and cloxacillin, and a moderate synergistic effect on the others, except ampicillin.