• Customer Questions About Chromogenic Media

Bile Agar (BGBA) are used. Unfortu-nately, these selective media do not clearly differentiate Salmonella spp. from the background bacterial flora associated with seed sprouts. Additional tests and time are required to confirm the identification of Salmonella spp. Due to this problem, our lab has engi-neered numerous Salmonella strains to express Green Fluorescent Protein (GFP) to allow for clear differentiation from non-Salmonella bacteria as well as being able to use nonselective media to enumerate injured cells. However, at low dilution levels, the GFP-Salmonella are masked due to the high numbers of normal background bacteria. Recently, a media comparison study was performed that involved BSA, BBL ™ CHROMagar ™ Salmonella and nonselective Tryptic Soy Agar (TSA) for the isolation of Salmonella spp. from alfalfa seeds and sprouts. Initially, a 5-strain cocktail of S. enterica as described above was inoculated onto alfalfa seeds as described by Hu et al. (2004)1 and subjected to 55°C for a period of 6 days. Samples of heat-treated seeds were taken periodically and sampled for levels of Salmonella spp. A portion of the sample was allowed to sprout at 30°C with misting and then enumerated for Salmonella in the finished sprouts. Representative samples of heat-treated seeds and sprouted seeds from the variou