MYP Agar Base (Phenol Red Egg Yolk Polymyxin Agar Base)

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SKU:
M636S
Used for isolation and identification of pathogenic Staphylococci and Bacillus species as recommended by BIS committee under the specifications IS:5887(Part V)-1976.


Composition**

Ingredients Gms/Litre
Peptic digest of animal tissue 10.000
Meat extract 1.000
D-Mannitol 10.000
Sodium chloride 10.000
Phenol red 0.025
Agar 15.000
Final pH (at 25°C) 7.2±0.1

**Formula adjusted, standardized to suit performance parameters

Directions

Suspend 46.03 grams in 900 ml distilled water. Heat to boiling to dissolve the medium completely. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. Cool to 55°C. Aseptically add sterile Polymyxin B Sulphate (FD003) solution to a final concentration of 100 units per ml and 100 ml sterile Egg Yolk Emulsion (FD045) per 1000 ml medium. Mix well and pour into sterile Petri plates.

Principle And Interpretation

Mannitol Yolk Polymyxin (MYP) Agar was formulated by Mossel et al (1) and is recommended by APHA (2) for enumeration of Bacillus cereus When present in large numbers in certain foodstuffs, Bacillus cereus can produce metabolites responsible for the clinical symptoms of food poisoning (3). MYP Agar Base is recommended by BIS for isolation and enumeration of Bacillus cereus. (4).

The medium contains peptic digest of animal tissue and meat extract which provide nitrogen source. Mannitol fermentation can be detected with the phenol red, which yields yellow colour to the mannitol fermenting colonies. Added egg yolk emulsion helps in differentiation of lecithinase producing colonies which are surrounded by a zone of white precipitate. Addition of Polymyxin B Sulphate helps to restrict growth of gram-negative bacteria such as Escherichia coli and Pseudomonas aeruginosa. These differentiating media allow differentiation of Bacillus cereus from other Bacillus species by its inability to ferment mannitol and poor sporulation. Acid produced by organisms other than Bacillus cereus often diffuse through the medium, making it difficult to distinguish between mannitol fermenters and nonfermenters. So it is advised to transfer the suspected colonies to a fresh medium to ascertain the true reaction.

Colonies from MYP Agar are subcultured on Nutrient Agar and incubated at 30°C for 24 hours to observe/determine vegetative cells, sporangium and spore morphology and lipid globules within vegetative cell.

Quality Control

Appearance
Light yellow to light pink homogeneous free flowing powder

Gelling
Firm, comparable with 1.5% Agar gel

Colour and Clarity of prepared medium
Basal medium : Red coloured clear to slightly opalescent gel. After Addition of Egg Yolk Emulsion (FD045) : Light orange coloured opaque gel forms in Petri plates

Reaction
Reaction of 4.6% w/v aqueous solution at 25°C. pH: 7.2±0.1

Cultural Response

pH
7.10-7.30

M636S: Cultural characteristics observed with added Egg Yolk Emulsion (FD045)and Polymyxin B Sulphate(FD003) after an incubation at 32°C for 18-40 hours.

Organism Inoculum (CFU) Growth Recovery Colour of colony Lecithinase activity
Bacillus cereus ATCC 10876 50-100 luxuriant >=50% red positive, opaque zone around the colony
Bacillus subtilis ATCC 6633 50-100 luxuriant >=50% yellow negative
Escherichia coli ATCC 25922 50-100 none-poor <=10%
Proteus mirabilis ATCC 25933 50-100 luxuriant >=50% red negative
Pseudomonas aeruginosa ATCC 27853 50-100 none-poor <=10%
Staphylococcus aureus ATCC 25923 50-100 luxuriant >=50% yellow positive, opaque zone around the colony

Storage and Shelf Life

Store below 30°C in tightly closed container and the prepared medium at 2 - 8°C. Use before expiry date on the label.

More Information
Product Name MYP Agar Base (Phenol Red Egg Yolk Polymyxin Agar Base)
SKU M636S
Product Type Regular
Physical Form Powder
Origin Animal
Packaging type HDPE
References 1.Bergdoll M. S., 1981, Clin. Microbiol. Newsletter 3: 85-87.
2.Centers for Disease Control: Bacillus cereus- Maine, MMWR, 35: 408-410, 1986.
3.Mossel D. A. A., Koopman M. J. and Jongerium E., 1967, Appl. Microbiol, 15:650.
4.Downes F. P. and Ito K., (Eds.), 2001, Compendium of Methods for the Microbiological Examination of Foods, 4th Ed.,APHA, Washington, D.C.
5.Nygren B., 1962, Acta Path. Microbiol. Scand., 56: Suppl. 1.
6.Donovan K. O., 1958, J. Appl. Bacteriol., 21:100.
7.Colimer A. R., 1948, J. Bacteriol., 55:777.
8.Rhodehamel J. and Harmon S. M., 1995, FDA Bacteriological Analytical Manual, 8th Ed., AOAC International,Gaithersburg, Md.
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