Overview:
Bacillus Cereus Agar Base (commonly known as MOSSel Agar or PEMBA when supplements are added) is the internationally recognized selective and differential solid medium for the isolation and enumeration of Bacillus cereus and other members of the B. cereus group from foods, cosmetics, and clinical samples. It is the reference method in ISO 7932, FDA-BAM Chapter 14, and most national standards. The combination of polymyxin, egg-yolk emulsion, and mannitol produces characteristic peacock-blue/green colonies with a clear egg-yolk precipitation halo (lecithinase-positive).
Applications:
?? Detection and enumeration of Bacillus cereus in foods (spices, dairy, rice, pasta, infant formula, etc.)
?? Official reference method ISO 7932 and FDA-BAM
?? Confirmation of emetic and diarrhoeal toxin-producing B. cereus group strains
?? Quality-control testing in food industry and public-health laboratories
Key Features:
?? Polymyxin B strongly inhibits Gram-negative bacteria and most Gram-positives
?? Mannitol not fermented ? red/pink background
?? Egg-yolk emulsion ? turquoise to peacock-blue colonies with opaque lecithinase halo
?? Highly specific and reproducible
Composition (per liter � base only):
Peptone    � 10.0 g
Mannitol     � 10.0 g
Sodium Chloride (NaCl)  � 5.0 g
Magnesium Sulfate (MgSO?�7H?O)� 0.1 g
Disodium Phosphate (Na?HPO?)  � 2.5 g
Monopotassium Phosphate (KH?PO?)� 0.25 g
Bromothymol Blue   � 0.12 g
Sodium Pyruvate � 1.0 g (enhances sporulation)
Agar� 15.0 g
Final pH: 7.2 � 0.2 at 25�C
Supplements (added after autoclaving, cooled to 50�C):
Polymyxin B Supplement        � 100,000 IU/L (or 10 mg pure polymyxin B)
Egg-Yolk Emulsion (50 %)  � 100 mL/L (or Egg-Yolk Tellurite Emulsion in some versions)
Preparation:
Suspend 43.97 g of dehydrated base in 900 mL purified water.
Boil to dissolve completely.
Autoclave at 121�C for 15 minutes.
Cool to 50�C.
Aseptically add filter-sterilized Polymyxin B and 100 mL sterile Egg-Yolk Emulsion.
Mix well and pour into sterile plates.
Typical colony appearance (after 24�48 h at 30�32�C):
Bacillus cereus group: 3�7 mm, peacock-blue to turquoise, rough/matte surface, surrounded by wide egg-yolk precipitation zone
Other bacteria: inhibited or small pink/red colonies without halo
Storage:
Dehydrated base: cool, dry place below 30�C
Prepared plates: 2�8�C, protected from light, use within 3 weeks
For laboratory food and environmental microbiology use only. Official ISO 7932 reference medium.