Part of Thermo Fisher Scientific
Organisms this product works with:
Other products used in the isolation of Staphylococcus sp:
BAIRD-PARKER AGAR BASE (RPF)
Code: CM0961
a new improved base medium for use with RPF Supplement (SR0122). This conforms to ISO 6888 Part 21 for the enumeration of coagulase-positive staphylococci.
Typical Formula* |
gm/litre |
Pancreatic digest of casein |
10.0 |
Meat extract |
5.0 |
Sodium pyruvate |
10.0 |
Yeast extract |
1.0 |
Glycine |
12.0 |
Lithium chloride |
5.0 |
Agar |
20.0 |
pH 7.2 ± 0.2 @ 25ºC |
RPF SUPPLEMENT
Code: SR0122
Typical Formula |
SR0122A |
per litre
|
Bovine fibrinogen |
375mg |
3.75g |
Rabbit plasma |
2.5ml |
25.0ml |
Trypsin inhibitor |
2.5mg |
25.0mg |
Potassium tellurite |
2.5mg |
25.0mg |
Directions
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.
N.B.: Baird-Parker Agar Base (RPF) should only be used with RPF Supplement SR0122
Description
Staphylococcus aureus is a Gram-positive coccus capable of producing enterotoxin which can induce food poisoning. The organisms may be present in small numbers in many foods, and, if allowed to multiply unchecked, may produce highly heat resistant enterotoxins. The ability of Staphylococcus aureus to produce lecithinase and lipase has been recognised for many years, and the detection of these enzymes in egg yolk media has become a widely used procedure for the identification of this organism. Its ability to produce coagulase using a similar basal formulation enables confirmatory diagnosis with the incorporation of rabbit plasma into the base medium.
Rabbit Plasma Fibrinogen (RPF) Agar is based on the formulation described by Beckers et al2. This medium is a modification of Baird-Parker Medium and is recommended for the selective isolation, enumeration and confirmation of Staphylococcus aureus from food and other specimens3. The RPF Agar formulation retains the Baird-Parker Agar Base which has been specifically formulated to resuscitate injured cells4. This medium differs from Baird-Parker Medium in that the egg yolk emulsion has been replaced by fibrinogen, rabbit plasma and trypsin inhibitor. The fibrinogen was added to enhance the coagulase reaction in the RPF Agar5. The addition of rabbit plasma was found to be more specific for the coagulase activity when compared to other sources of plasma2. Trypsin inhibitor was added to prevent fibrinolysis.
The RPF Supplement (SR0122) has been modified in one respect from the original formulation, in that the potassium tellurite content has been reduced four-fold, from 0.01% to 0.0025% w/v. This reduction was necessary as it was discovered in the Oxoid laboratory that some strains of Staphylococcus aureus were sensitive to potassium tellurite when used at 0.01% w/v in RPF Agar6. This modification of RPF Agar was found to give comparable growth and selectivity to that achieved on Baird-Parker Medium (CM0275 or CM1127 and SR0054). The improved productivity of RPF Agar has also been confirmed by other laboratories7,8. The reduction in potassium tellurite concentration in RPF Agar results in Staphylococcus aureus strains forming white, grey or black colonies, which are surrounded by an opaque halo of precipitation, i.e. the coagulase reaction.
Technique
Surface Inoculation Method
Pour Plate Method
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 prepared1,2.
Appearance
Dehydrated medium: Straw coloured, free-flowing powder
Prepared medium: Straw coloured gel
Quality Control
Quality control of the medium includes testing in accordance with ISO 111339.
Positive control: |
Expected results |
Staphylococcus aureus ATCC® 25923* WDCM00034 |
1-3 mm grey/black colonies coagulase zones |
Negative control: |
|
Staphylococcus saprophyticus ATCC® 15305* WDCM00159 |
No growth pinpoint - 2 mm grey/black colonies, no zone |
Escherichia coli ATCC® 25922* WDCM00013 |
No growth |
Precautions
Colonies of some contaminating organisms growing in close proximity to the coagulase positive colonies may partially digest the coagulase halo reaction.
References
1. International Organization for Standardization ISO 6888-2 (1999) Microbiology of food and animal feeding stuffs - Enumeration of coagulase positive staphylococci (Staphylococcus aureus and other species) – Part 2 Technique using rabbit plasma fibrinogen agar.
2. Beckers H. J., van Leusden F. M., Hogeboom W. M. and Delfgon-van Asch E. H. M. (1980) (English summary) De Ware(n)-Chemicals 10. 125-130.
3. Beckers H. J., van Leusden F. M., Bindshedler O. and Guerraz D. (1984) Can. J. Microbiol. 30. 470-474.
4. Baird-Parker A. C. (1962) J. Appl. Bacteriol. 25. 12-19.
5. Hauschild A. H. W., Park C. E. and Hilsheimer R. (1979) Can. J. Microbiol. 25. 1052-1057.
6. Sawhney D. (1986) J. Appl. Bact. 61. 149-155.
7. Beckers H. J. (1985) Personal Communication.
8. van Schothorst M. (1985) Personal Communication.
9. International Organization for Standardization ISO 11133:2014 Microbiology of food, animal feed and water - Preparation, production, storage and performance testing of culture media