Baird Parker Agar Base

Intended Use

Recommended for the enumeration of coagulase positive Staphylococci from food and animal feeding stuffs. The composition and performance criteria are as per the specification laid down in ISO 6888-1:1999 / Amd :2018 and ISO 11133:2014 & Amd. 2:2020 (Ε).

Composition

ISO specification -Baird-Parker agar medium

Baird Parker Agar Base M0431

Final pH after sterilization (at 25°C): 7.2±0.2 (for both)

**Formula adjusted, standardized to suit performance parameters

# Equivalent to Pancreatic digest of casein,

## Equivalent to Meat extract

Supplements to be added after autoclaving per 1000ml of medium

Directions

Suspend 58.0 gram in 1000 ml purified / distilled water. Heat to boiling to dissolve the medium completely. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. Cool to 45-50°C and aseptically add 50 ml concentrated Egg Yolk Emulsion (FD045) and 10 ml sterile PTe 1% Selective Supplement (1 ml per vial) (FD052). If desired add rehydrated contents of 1 vial of BP S Selective Supplement (FD069). Mix well and pour into sterile Petri plates.

Principle And Interpretation

Baird Parker Agar was developed by Baird Parker (1,2) from the Tellurite-glycine formulation of Zebovitz et al (3) for isolation and enumeration of Staphylococci in food and other material since it allows a good differentiation. The composition laid down is as per ISO 6888-1 (4). A high correlation has been found between the coagulase test and the presence of clear zone of lypolysis in this medium, which is due to the lecithinase of Staphylococci that breakdown, the egg yolk. On the other hand, studies show that almost 100% of coagulase positive Staphylococci are capable of reducing tellurite, which produces black colonies, whereas other Staphylococci cannot always do so. The identity of Staphylococcus aureus isolated on Baird-Parker Agar must be confirmed with a coagulase reaction. Baird-Parker Agar can also be used to detect coagulase activity by adding fibrinogen plasma (5). Smith and Baird-Parker (6) found that the addition of 50 mg/l Sulphamethazine in the medium, suppresses the growth and swarming of Proteus species.

Tryptone, HM extract and yeast extract are sources of nitrogen, carbon, sulphur and vitamins. Sodium pyruvate not only protects injured cells and helps recovery but also stimulates Staphylococcus aureus growth destroying selectivity. Lithium chloride and potassium tellurite inhibit most of the contaminating microflora except Staphylococcus aureus. The tellurite additive is toxic to egg yolk-clearing strains other than S.aureus and imparts a grey to black colour to the colonies. Glycine, pyruvate enhances growth of Staphylococcus. With the addition of egg yolk, the medium becomes yellow, opaque. The egg yolk additive, in addition to provide enrichment, aids in the identification process by demonstrating lecithinase activity (egg yolk reaction). A clear zone and grey-black colonies on this medium are diagnostic for coagulase positive Staphylococci. Upon further incubation, an opaque zone is developed around colonies, which can be due to lipolytic activity. Testing of medium is carried out as per ISO 11133:2014 (7)

Type of specimen

Food samples and animal feeding stuffs

Specimen Collection and Handling

For food samples, follow appropriate techniques for sample collection and processing as per guidelines (4,7).

After use, contaminated materials must be sterilized by autoclaving before discarding.

Warning and Precautions

Read the label before opening the container. Wear protective gloves/protective clothing/eye protection/face protection. Follow good microbiological lab practices while handling specimens and culture. Standard precautions as per established guidelines should be followed while handling specimens. Safety guidelines may be referred in individual safety data sheets.

Limitations

1. The identity of Staphylococcus aureus isolated on Baird-Parker Agar must be confirmed with a coagulase reaction.

Performance and Evaluation

Performance of the medium is expected when used as per the direction on the label within the expiry period when stored at recommended temperature.

Quality Control

Appearance: Cream to yellow homogeneous free flowing powder

Gelling: Firm, comparable with 1.5% agar gel.

Colour and Clarity of prepared medium: Basal medium: Yellow coloured clear to slightly opalescent gel. After addition of Egg Yolk Emulsion and Tellurite solution: Yellow coloured opaque gel forms in Petri plates.

Reaction: Reaction of 5.8% w/v aqueous solution at 25°C. pH : 7.2±0.2

pH: 7.00-7.40

Cultural Response

Productivity: Cultural response was observed with added Egg Yolk Emulsion (FD045) and sterile PTe 1% Selective Supplement (FD052) after an incubation at 37±1°C for 24±2 to 48 ±2 hours. Recovery rate is considered as 100% for bacteria growth on Reference medium - Soyabean Casein Digest Agar (Tryptone Soya Agar).

Specificity: Cultural response was observed with added Egg Yolk Emulsion (FD045) and sterile PTe 1% Selective Supplement (FD052), after an incubation at 37°1°C for 24-48°2 hours.

Selectivity: Cultural response was observed with added Egg Yolk Emulsion (FD045) and sterile PTe 1% Selective Supplement (FD052), after an incubation at 37°1°C for 48°2 hours.

Key: (*) - Corresponding WDCM numbers

Storage and Shelf Life

Store between 10-30°C in a tightly closed container and the prepared medium at 2-8°C. Use before expiry date on the label. On opening, product should be properly stored dry, after tightly capping the bottle in order to prevent lump formation due to the hygroscopic nature of the product. Improper storage of the product may lead to lump formation. Store in dry ventilated area protected from extremes of temperature and sources of ignition. Seal the container tightly after use. Product performance is best if used within stated expiry period.

Disposal

User must ensure safe disposal by autoclaving and/or incineration of used or unusable preparations of this product. Follow established laboratory procedures in disposing of infectious materials and material that comes into contact with sample must be decontaminated and disposed of in accordance with current laboratory techniques (8,9).

References

1. Baird-Parker A. C., 1962, J. Appl. Bacteriol., 25:12.
2. Baird-Parker A. C. and Davenport E., 1965, J. Appl. Bacteriol., 28:390
3. Zebovitz E., Evans J. B. and Niven C.F., 1955, J. Bacteriol., 70:686.
4. Microbiology of food and animal feeding stuffs - Horizontal method for the enumeration of coagulase positive Staphylococci (Staphylococcus aureus and other species). International Organization for Standardization (ISO), ISO 6888-1:1999 / Amd 2:2018-07.
5. Beckers N. J. et al, 1984, Can. J. Microbiol., 30:470.
6. Smith B. A. and Baird-Parker A.C., 1964, J. Appl. Bacteriol., 27:78.
7. Microbiology of food, animal feeding stuffs and water- Preparation, production, storage and performance testing of culture media, EN ISO 11133:2014 & Amd. 2 :2020 (E).
8. Isenberg, H.D. Clinical Microbiology Procedures Handbook 2nd Edition.
9. Jorgensen, J.H., Pfaller, M.A., Carroll, K.C., Funke, G., Landry, M.L., Richter, S.S and Warnock., D.W. (2015) Manual of Clinical Microbiology, 11th Edition. Vol. 1.