MRS Agar

Item No.  NCM0190A

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MRS Agar is a medium for the enumeration of mesophilic lactic acid bacteria according to ISO 15214:1998, and is not intended for use in the diagnosis of disease or other conditions in humans.

MRS Agar was originally developed in 1960 by de Man, Rogosa & Sharpe for the cultivation and enumeration of Lactobacillus spp. from various sources and is intended as a substitute for Tomato Juice Agar. This original formulation has been adapted and adjusted to pH 5.7 according to ISO 15214:1998.

Nutrition is provided by enzymatic digest of casein, glucose, meat & yeast extracts whilst polyoxyethylenesorbitan monooleate, magnesium and manganese sulphates act as growth stimulants. Selectivity against streptococci & molds is provided by ammonium citrate and sodium acetate. Used at low pH, ammonium citrate allows growth of lactobacilli whilst inhibiting a number of other organism groups.

Occasionally, sterilization of this medium at 121°C can cause the pH to fall outside of the specified pH limits 5.7 +/- 0.1. In these rare cases adjustment of the medium using acetic acid or sodium hydroxide is recommended.

Analyte Lactobacillus spp.
Brand NEOGEN® Culture Media
Formula Liter
Enzymatic Digest of Casein 10.0 g/L
Meat Extract 10.0 g/L
Yeast Extract 4.0 g/L
Triammonium Citrate 2.0 g/L
Sodium Acetate 5.0 g/L
Magnesium Sulphate Heptahydrate 0.2 g/L
Manganese Sulphate Tetrahydrate 0.05 g/L
Dipotassium Hydrogen Phosphate 2.0 g/L
Glucose 20.0 g/L
Polyoxyethylenesorbitan Monooleate 1.08 g/L
Agar 15.5 g/L
Grams per Litre 70.00
Litres per 500g 7.00
Mass 500 g
Package Dimensions 4.60 IN x 2.90 IN x 8.60 IN
Package Weight 1.35 LB
Plates per 500g 390.00
  1. Suspend 70 grams of the medium in one liter of purified water.
  2. Heat with frequent agitation and boil for one minute to completely dissolve the medium.
  3. Autoclave at 121ºC for 15 minutes.
  4. Cool to 45-50ºC.
Previous Item Number Product was previously known as LabM Product: LAB223 MRS Agar (ISO)



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