Description
R2A medium was primarily developed because it had become apparent to authorities working in the area of water & waste water testing that the results they were producing using the current methods & mediums available was only representing a fraction of the microbial population actually present. Organisms were failing to be detected either because they grew too slowly to be included in colony counts after 48 hours incubation, because they were too damaged to grow on the media available or conditions were not optimum for growth of non coliform bacteria.
R2A medium developed from the work of Reasoner & Geldreich1 is similar to modified Henrici medium & casein-peptone-starch media, minus the glycerol or iron (as FeCl3 or FESO4). As part of their trial, Reasoner & Geldreich compared seven medium/method combinations incorporating PCA & R2A using SPC (standard plate count), spread plate & membrane filter plate methods.
