A selective culture medium for separating listeria monocytogenes by taking benefit from propolis (bee glue)

High incidence of food listeriosis, especially listeriosis resulted from consumption of diary products has been reported to be as the second lethal cause resulted from food contamination after salmonella. Due to the importance of rapid diagnosis and treatment of this bacterium, there is a need to provide suitable culture medium for listeria growth and separating it from contaminated food products. The aim of this study was to investigate the possibility of applying a natural substance ;propolis (bee glue); in order to make a selective culture medium for separating listeria.Crude samples of propolis collected from 3 different regions were diluted in 30 ml of 70% ethanol. After performing the Minimal Inhibitory Concentration (MIC) and finding the effective concentration of propolis for listeria monocytogenes to grow and preparation of different dilutions, propolis was added to 170 plates containing 4 various media including Muller Hinton Broth, Blood Agar, Muller Hinton Agar and Brain Heart Infusion Agar and different strains of bacteria were cultured. All bacterial strains growth including: E.coli, Shigella flexeneri, Klebsiella pneumoniae, Staphylococcus auricularis, Shigella sounei, Pseudomonas aeroginosa, Salmonella typhi murium, Enterobacter aeroginosa and Staphylococcus aureus was inhibited except for listeria monocytogenes. The effect of propolis for separating listeria monocytogenes was proved as the main effective substance in the new media.