In vitro antibacterial activity and total phenolic content of propolis alcoholic extracts

The aim of the present study was to investigate the antibacterial activities of 25 propolis samples collected from 9 various geographical provinces of Syria and 3 samples from Amman, Jordan, compared with 3 commercial samples, against 8 food-borne bacterial pathogens (4 gram-positive: Bacillus cereus, B. subtilis, Staphylococcus haemolyticus, S. lugdunensis and 4 gram-negative: Citrobacter braakii, Enterobacter cloacae, Proteus mirabilis, Salmonella enteritidis). The total phenolic content of ethylnolic extracts of propolis (EEP) ranged between 281 and 3046 mg/100 g. Antibacterial activities of EEP samples were tested in dilutions of 1:20 to 1:1280 dilutions of Meuller Hinton Broth (MHB). The most resistant species to propolis extracts were Salmonella enteritidis and Bacillus cereus, whereas Enterobacter cloacae and Staphylococcus haemolyticus were the most sensitive among all Gram negative and positive tested bacteria.