A Review and Testing of Selective Media for Psychrotrophic Bacteria

A thorough review of the literature revealed numerous selective media developed for culturing psychrotrophic spoilage bacteria of foods. Diamide (diazenedicarboxylic acid bisdimethylamide), cetrimide (cetyltrimethylammonium bromide), or cephaloridine were added to two nutrient media and eight media previously reported for selectively culturing pseudomonads and other psychrotrophic spoilage bacteria of foods. Four strains of bacteria associated with poultry spoilage and 9 strains suspected of interfering with the selectivity of the media were cultured. The addition of .025% diamide inhibited all the unwanted strains tested except Pseudomonas aeruginosa. It also inhibited P. fragi but permitted growth of P. fluorescens and P. putida. Cetrimide at 10 ppm allowed the growth of P. fragi but did not inhibit two Enterobacter strains. Cephaloridine inhibited E. coli and Proteus vulgaris while permitting growth of P. aeruginosa, fluorescens, and putida.