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Baird Parker Agar Base, Oxoid is suitable for the isolation and enumeration of Staphylococcus aureus, with high selectivity and sensitivity. It contains carefully balanced selective inhibitory agents, glycine, lithium, and tellurite, to suppress the growth of most of the bacteria present in foods without inhibiting coagulase-positive staphylococci. The presence of egg yolk emulsion and sodium pyruvate aid the recovery of damaged cells for presumptive identification of Staphylococcus aureus in food specimens.

Baird Parker Agar Base, Oxoid Preparation:

Suspend 6.3g of Baird-Parker Agar Base (RPF) in 90ml of distilled water. Bring to the boil to dissolve completely. Sterilise by autoclaving at 121ºC for 15 minutes. Cool to 48ºC and add 1 vial of RPF Supplement (SR0122A), reconstituted as directed. Mix well and pour plates.

Storage Conditions and Shelf Life
Store the dehydrated medium at 10-30°C and RPF Supplement below 0°C. Use before the expiry date on the label.
Prepared plates of the medium are best used freshly prepared.

Precautions
Regard all suspicious colonies as Staphylococcus aureus regardless of negative reactions in the medium and carry out further tests.
Colonies of some contaminating organisms growing in close proximity to the coagulase positive colonies may partially digest the coagulase halo reaction.

A modified medium requiring the addition of basic fuchsin to form Endo Agar.

• Oxoid Endo Agar is an APHA recommended medium for the confirmation of coliforms.
• Also available Basic Fuchsin Indicator, Part No. BR0050A.

Endo Agar Base, Oxoid Composition

Endo Agar, Oxoid Preparation:
Suspend 36g in 1 litre of distilled water. Add 6ml (or as directed by the supplier) of a 10% w/v solution of basic fuchsin BR0050 (50:50 ethanol/distilled water). Bring to the boil to dissolve completely. Sterilise by autoclaving at 121°C for 15 minutes. Mix well before pouring. Plates should be stored in the dark to preserve their pale pink colour.

BASIC FUCHSIN IS A POTENTIAL CARCINOGEN AND CARE SHOULD BE TAKEN TO AVOID INHALATION OF THE POWDERED DYE AND CONTAMINATION OF THE SKIN.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared plates at 2-8°C away from light.

Precautions
Weigh out the basic fuchsin (BR0050) in a fume cupboard and avoid inhalation of the powder or contamination of the skin.
Keep the prepared medium away from light to avoid photo-oxidation.
Endo Agar is quoted by the American Public Health Association as a `Standard Methods’ medium for use in water¹ and dairy products. Windle Taylor recommended the medium for the isolation and differentiation of coli-aerogenes bacteria from water.

Oxoid MRVP Medium. A glucose-phosphate medium is used for the differentiation of the coli-aerogenes group by the Methyl Red and Voges-Proskauer tests.

MRVP Medium, Oxoid Composition

MRVP Medium, Oxoid Preparation:
Add 17g to 1 litre of distilled water. Mix well, distribute into final containers and sterilise by autoclaving at 121°C for 15 minutes.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared medium at 2-6°C.

Precautions
The MR-VP reactions are only part of the tests required to identify organisms.
Each laboratory should standardise on the inoculum density, volume of broth and the test container size.
MR tests require a minimum incubation of 48 hours before the pH indicator is added.
When using Barritt’s reagents add a-naphthol first and KOH second; do not reverse this order.
Vaughn et al. warned of false positive VP reactions if the completed tests are left standing for over an hour.