Baird Parker Agar w/o Egg Yolk Emulsion

Intended Use

Recommended for direct enumeration of coagulase positive staphylococci without using Egg yolk emulsion.

Composition**

Final pH (at 25°C): 7.0±0.2

**Formula adjusted, standardized to suit performance parameters # - Equivalent to Beef extract

Directions

Suspend 47.73 grams (the equivalent weight of dehydrated media per litre) 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. 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 of coagulase positive strains. A high correlation has been found between the coagulase test and the presence of clear zone of lipolysis in this medium, which is due to the lecithinase of Staphylococci that breakdown, the egg yolk. The limitation of the medium is inadequacy of the egg yolk clearing activity to differentiate S. aureus from other contaminant bacteria (4). Baird Parker Agar without the addition of Egg Yolk Emulsion for isolation of Staphylococci from food samples was found to be less inhibitory to Staphylococcus aureus than other media at the same time being more selective (5,6,7). This medium successfully replaces Egg yolk emulsion with Tween 80 and Magnesium chloride. The efficacy of the medium was compared with Baird Parker Agar Base, and the results were found to be comparable.

Tryptone, HM peptone B and yeast extract are sources of nitrogen, carbon, long chain amino acids, sulphur and vitamins. Tween 80 and Magnesium ions helps for identification of coagulase activity. Maltose is the source of carbohydrate. Sodium acetate has an inhibitory effect on gram-negative bacteria.

Alternatively the medium can also be tested using Fibrinogen Plasma Trypsin Inhibitor supplement (FD195). On this medium, coagulase positive colonies appear white to grey-black surrounded by an opaque zone due to coagulase activity within 24-48 hours incubation at 35°C. Reduction in tellurite is necessary because of absence of egg yolk emulsion. This results in translucent agar and white to grey coloured colonies of Staphylococci.

Type of specimen

Clinical samples-pus, wounds, skin lesions, etc ; Food samples

Specimen Collection and Handling

For clinical samples, follow appropriate techniques for sample collection and processing as per guidelines (8,9).

For food samples, follow appropriate techniques for sample collection and processing as per guidelines (10).

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

Warning and Precautions

In Vitro diagnostic use. For professional use only. 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 clinical specimens. Safety guidelines may be referred in individual safety data sheets.

Limitations

1. Though the medium is recommended for detection of coagulase positive Staphylococcus aureus, other bacteria may grow.
2. Certain stressed cell of Staphylococcus aureus may show poor growth.
3. Further biochemical test have to be performed for confirmation.

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 1.2% agar gel.

Colour and Clarity of prepared medium: Light yellow coloured slightly opalescent gel forms in Petri plates.

Reaction: Reaction of 4.8% w/v aqueous solution at 25°C. pH : 7.0±0.2

pH: 6.80-7.20

Cultural Response: Cultural response was observed after an incubation at 35-37°C for 24-48 hours. Recovery rate is considered as 100% for bacteria growth on Soyabean Casein Digest Agar.

Key : (*) Corresponding WDCM numbers.

Storage and Shelf Life

Store between 10-30°C in a tightly closed container and the prepared medium at 20-30°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 clinical sample must be decontaminated and disposed of in accordance with current laboratory techniques (8,9).

Reference

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.Assoc. off. Anal. Chem., 1971, 54:401.
3. Zebovitz E., Evans J. B. and Niven C.F., 1955, J. Bacteriol., 70:686.
4. R. Victoria Lachica, 1984 Egg Yolk-Free Baird-Parker Medium for the Accelerated Enumeration of Foodborne Staphylococcus aureus.
5. Assoc. off. Anal. Chem., 1971, 54:401.
6. Baer, 1971, J. Assoc. Off. Anal. Chem., 54:732.
7. Tardio and Baer, 1971, J. Assoc. Off. Anal. Chem., 54:728.
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.
10. Salfinger Y., and Tortorello M.L., 2015, Compendium of Methods for the Microbiological Examination of Foods, 5th Ed., American Public Health Association, Washington, D.C.