The antimicrobial potential of ten propolis samples from Transylvania was investigated using a disk diffusion method and a broth microdilution assay. The three most active samples were tested for post antibiotic effect (PAE) against Pseudomonas aeruginosa and Staphylococcus intermedius. The results pointed out a complex antibacterial activity as indicated by the values obtained for the inhibition zones (10–23.5mm) and for the minimal inhibitory (MIC) and bactericidal (MBC) concentrations (0.125%-1% v/v). The bactericidal efficacy was demonstrated against both Gram positive and Gram negative, but proved to be diminished in enrofloxacin-resistant bacterial strains. A positive correlation was found between these data and propolis composition in biologically active compounds – phenolics – determined by spectrophotometric and chromatographic methods (Folin Ciocalteu and HPLC-PDA). According to these results Transylvanian propolis presented typical poplar profile with high concentration in total phenolics 33,02±9,04% and medium amount in total flavonoids 6,8±1,48%.
