Seasonal effect on Brazilian propolis antibacterial activity

The behavior of microorganisms towards the antibiotic action of propolis ha s been widely investigated. Since reports dealing with seasonal effect on p ropolis activity are not available, this assay was carried out aiming to ob serve the in vitro antimicrobial activity of propolis, collected during the four seasons, on bacterial strains isolated from human infections. Dilutio n of ethanolic extract of propolis (EEP) in agar was the method performed, with serial concentrations ranging from 0.4 to 14.0% (% v/v). The behavior of some bacteria was analysed according to the incubation period in medium plus propolis, and the survival curve was plotted. It was verified that the growth of Gram-positive bacteria is inhibited by low propolis concentratio ns (0.4%) whereas Gram-negative bacteria were less susceptible to this subs tance, the minimal inhibitory concentration ranging from 4.5 to 8.0%. There was no significant difference with regards to the seasonal effect on the s urvival curve of Staphylococcus aureus and Escherichia coli; after incubati on with propolis, there was an efficient antimicrobial action, mainly towar ds Gram-positive bacteria. (C) 2000 Elsevier Science Ireland Ltd. All right s reserved.