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de Man, Rogosa & Sharpe (MRS) Agar M.R.S. Agar is intended for the cultivation and enumeration of Lactobacillus spp from a variety of sources and can be used as an alternative to Orange Serum Agar for that purpose. Magnesium Sulphate, Manganese Sulphate, Sodium Acetate and Tween are included as growth supplements. The medium can be made more specific for lactobacilli generally by lowering the pH to between 5.0 and 5.5. This has the effect of inhibiting most streptococci that may otherwise grow on the medium and can be readily confused with lactobacilli. -
Recent developments in culture media have given rise to the use of chromogenic substrates as a means of differentiating bacteria particularly among the coliform group of organisms. This is one such medium and has been developed primarily as a selective medium for the isolation and enumeration of Escherichia coli in food samples. Based on Tryptone Bile Agar it incorporates the chromogenic agent X-glucuronide, which detects glucuronidase activity, the same enzyme as is detected by MUG reagent. Escherichia coli can be differentiated from other coliform organisms by the presence of glucuronidase resulting in the colonies being blue/green while the other coliforms are colourless. For information on the full technical detail as to the functionality of this medium reference should be made to the many publications available.
