Rogosa SL Agar

This selective medium was modified by Rogosa to contain high levels of sodium acetate and ammonium citrate at a low pH, which inhibits most microorganisms, including streptococci and molds, and limits swarming but allows the growth of lactobacilli.

Sucrose, arabinose and dextrose are fermentable carbohydrates as carbon and energy sources. Tryptone provides nitrogen, vitamins, minerals and amino acids essential for growth. Yeast extract is a source of vitamins, particularly of the B-group. Sulfate salts provide inorganic ions. Polysorbate 80 is a surfactant and is incorporated to neutralize phenols, hexachlorophene and formalin. Monopotassium phosphate acts as a buffer system. Bacteriological agar is the solidifying agent.

Typical formula in g/L, adjusted and/or supplemented as required to meet performance criteria.

Preparation

Suspend 75 grams of the medium in one liter of distilled water. Mix well and dissolve by heating with frequent agitation. Boil for one minute until complete dissolution. Add 1.32 mL of glacial acetic acid and mix well. Heat again at 90-100 °C for two minutes. DO NOT AUTOCLAVE. Cool the medium to 40-45 °C and dispense into appropriate sterilized containers.

Instructions for use

1. Direct inoculation or plate count methodologies can be used.
2. Inoculate the medium and incubate at 35 ± 2 °C for 24-48 hours.

• Rogosa, M., J. A. Mitchell and R.F. Wiseman. 1951. A selective medium for the isolation and enumeration of oral and fecal lactobacilli. J. Dental Res. 30:682.
• MacFaddin, J. D. 1985. Media for isolation-cultivation-identification-maintenance of medical bacteria, vol. 1. p. 678-680. Williams & Wilkins, Baltimore, M.D.