Microbiology

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.

Isolate, enumerate, and identify coagulase positive Staphylococcus aureus in food samples with selective Thermo Scientific™ Oxoid™ Baird Parker Agar (ISO) Base (Dehydrated) while adhering to ISO 6888-1:1999.

Baird Parker Agar (ISO) Base, Oxoid Composition

Baird Parker Agar (ISO) Base, Oxoid Preparation:
Suspend 63g of Baird-Parker Agar (ISO) Base in 1,000ml of distilled water. Boil to dissolve the medium and sterilise by autoclaving at 121°C for 15 minutes. Cool to 47°C and aseptically add 50ml of Egg Yolk Tellurite Emulsion (SR0054). Mix well and pour into sterile Petri dishes.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
The prepared medium is best used freshly prepared, but may be suitable for longer storage following in-house validation.

Precautions
Atypical colonies have the same size as typical colonies but can be shining black with or without a narrow white edge; the clear zone or opacity halo can also be absent or barely visible. Grey colonies, free of clear zone, can also be regarded as atypical.
Regard all typical and atypical colonies as coagulase-positive staphylococci irrespective of negative reactions on 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.

• The Oxoid Baird-Parker RPF Agar Base is a selective medium for the isolation and enumeration of coagulase positive staphylococci from food.
• For use with RPF supplement, Part No. SR0122A
• Do not use Egg Yolk Tellurite Emulsion.

Baird-Parker Agar Base (RPF), Oxoid Composition

Baird-Parker Agar Base (RPF), 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 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 medium are best used freshly prepared.

Precautions
Colonies of some contaminating organisms growing in close proximity to the coagulase positive colonies may partially digest the coagulase halo reaction.

Oxoid Basic Fuchsin Indicator is a dye for use with Endo Agar Base, Part No. CM0479B and m Endo (LES) Agar Base, Part No. MM0551B.

Basic Fuchsin Preparation:

BR0050 should be dissolved to create a 10% w/v solution using 95% ethyl alcohol.

For each litre of culture medium use the amount described in the product reconstitution details.  This should be in a 10% w/v solution of the dye dissolved in 50:50 ethanol/distilled water.  E.g. For CM0479 add 6ml of a 10% w/v Basic Fuchsin solution per litre of medium.

The magenta dyes are closely related to known carcinogenic substances; therefore basic fuchsin should be handled with care, avoiding inhaling the powder or staining the skin with dye.

Oxoid BiGGY Agar (Nickerson Medium) for the isolation and presumptive identification of Candida spp.

BiGGY Agar, Oxoid Composition

BiGGY Agar, Oxoid Preparation:
Suspend 42g in 1 litre of distilled water and bring gently to the boil to dissolve the agar. Allow to cool to 50-55°C. Mix gently to disperse the flocculant precipitate and pour into sterile Petri dishes.
DO NOT AUTOCLAVE THE MEDIUM.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Medium should be freshly prepared just prior to use.

Precautions
Carry out further tests to confirm identity of isolated yeasts.
Do not use slants of medium because the reactions are unsatisfactory.
The flocculent precipitate present in the molten medium must be evenly suspended whilst dispensing the agar.

Isolate and presumptively identify enterococci / Group D streptococci with Thermo Scientific™ Oxoid™ Bile Aesculin Agar (Dehydrated). Bile Aesculin Agar is designed to differentiate between Group D streptococci and non-Group D streptococci.

Group D streptococci hydrolyse aesculin to form aesculetin and dextrose. Aesculin hydrolysis is indicative of a positive result. Bile salts in the medium inhibit Gram-positive bacteria other than enterococci/ Group D streptococci.

Bile Aesculin Agar, Oxoid Composition

Bile Aesculin Agar, Oxoid Preparation:
Suspend 44.5g in 1 litre of distilled water and bring gently to the boil to dissolve completely. 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.

Oxoid Bile Salts is a standardized ox-bile extract used as a selective inhibitory agent in culture media.

Oxoid Bile Salts No. 3 is a specifically refined fraction of bile acid salts.

• Normal working concentration 0.15% w/v.
• Each vial supplements 500mL of medium.

Isolate Salmonella typhi and other salmonllae from pathological material, sewage water supplies, food and other products with Thermo Scientific™ Oxoid™ Bismuth Sulphite Agar (Modified Wilson & Blair Medium) (Dehydrated). Bismuth Sulphite Agar is a modification of the original Wilson and Blair Medium and is particularly useful for the isolation of lactose-fermenting salmonellae. The presence of bismuth sulphite and brilliant green make this medium highly selective for salmonellae.

Bismuth Sulphite Agar, Oxoid Composition

Bismuth Sulphite Agar, Oxoid Preparation:
Suspend 20g in 500ml of distilled water in a 1 litre flask. Heat gently with frequent agitation until the medium just begins to boil and simmer for 30 seconds to dissolve the agar. Cool to 50-55°C, mix well to disperse suspension and pour thick plates (25 ml medium per plate). Allow the medium to solidify with the dish uncovered. Larger volumes may be prepared if great care is taken and adequate head space provided.
Dry the plates before use but take care to avoid overdrying. Correctly prepared plates should have a smooth, cream-like opacity with a pale straw colour. There should be no sedimentation of the indicator.
DO NOT OVERHEAT – DO NOT AUTOCLAVE

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label. Note the following comments:
Due to its contents of reactive and hygroscopic substances, dehydrated Bismuth Sulphite Agar quickly deteriorates when exposed to the atmosphere. This is usually indicated by aggregation into a solid non-friable mass, and by the development of a brown coloration. Medium reconstituted from such material is brown, does not become green on storage, and is characterised by loss of differential and selective properties. For this reason the powder should be stored in a cool, dry place and after use the container should be properly closed.

Precautions
Prepared plates of medium should not be stored for longer than two days at 2-8°C; after which time the dye oxidises to give a green medium that can be inhibitory to some salmonellae.

Shigella species are usually completely inhibited.

Salmonella sendai, Salmonella cholera-suis, Salmonella berta, Salmonella gallinarum and Salmonella abortus-equi are markedly inhibited.
It is important that the spreading technique yields well separated colonies. The typical colonial characteristics will not develop if the growth is too heavy or confluent; Salmonella typhi colonies will appear light green in these circumstances. Therefore, when in doubt, almost any growth on the medium should be subject to further tests.