BAM Media M95: Mannitol-Egg Yolk-Polymyxin (MYP) Agar

January 2001

Bacteriological Analytical Manual


Beef extract 1 g
Peptone 10 g
Mannitol 10 g
NaCl 10 g
Phenol red (1% solution in 95% ethanol) 2.5 ml
Agar 15 g
Distilled water 900 ml

Heat with agitation to dissolve agar. Adjust pH so that value after sterilization is 7.2 ± 0.2. Dispense 225 ml portions to 500 ml Erlenmeyer flasks. Autoclave 15 min at 121°C. Cool to 50°C. MYP agar is commercially available from Difco.

Polymyxin B solution, 0.1%

Dissolve 500,000 units polymyxin B sulfate in 50 ml distilled water. Filter-sterilize and store in the dark at 4°C until needed.

Egg yolk emulsion, 50%

(see M51). Also available from commercial suppliers.

Final medium

To 225 ml melted base add 2.5 ml polymyxin B solution and 12.5 ml egg yolk emulsion. Mix and dispense 18 ml portions to sterile 15 × 100 mm petri dishes. Dry plates at room temperature for 24 h before use.

Original Source: Bacteriological Analytical Manual, 8th Edition, Revision A, 1998.

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