INTENDED USE
MRS Agar is used for the growth and enumeration of cultures of Lactobacillus in dairy and other food
products and in animal feeding stuffs. The medium can be used to culture slowly-growing lactobacilli
such as Lactobacillus brevis and Lactobacillus fermentum. Acidified to low pH, it can be used to
enumerate Lactobacillus bulgaricus in yogurts. Following the NF / ISO standard 15214 for the
enumeration of mesophilic lactic acid bacteria, MRS agar should be used at pH 5.7. If yeast & mold
contamination in the sample being tested is of concern (for example in dry sausages), it is useful to add
sorbic acid to the medium in order to enhance inhibition. By addition of 0.1 mg of Clindamicine and 10
mg of Ciprofloxacine per liter, a medium known as MRS/CLC/CIP Agar can be obtained ; this medium
is used for the selective enumeration of Lactobacillus acidophilus in dairy products, according to the
standards ISO 20128 / IDF 192.
For the isolation and enumeration lactic acid bacteria in animal feeding stuffs, the pH of the MRS Agar
should be adjusted following the NF EN standards.