Baird Parker Agar

Description

The presence of tellurite and egg yolk allows the differentiation of presumptive pathogenic staphylococcal colonies. There is a high correlation between the coagulase test and the presence of clear zones of lipolysis in this medium, which is due to the staphylococcal lecithinase. 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.

Technique

Collect, dilute and prepare samples and volumes to be filtered as required according to specifications, directives, official standard regulations and/or expected results.

Filter the sample through a 0.45 µm pore membrane and apply it onto the surface of the agar.

Incubate the plates right side up, aerobically, at 37 ± 1.0 °C for 48 ± 2 h.

(Incubation times greater than those mentioned above or different incubation temperatures may be required depending on the sample, on the specifications, etc.)

After incubation, enumerate all the colonies on the surface of the membrane.

Calculate total microbial count per mL of sample by multiplying the average number of colonies per membrane by the inverse dilution factor. Report results as colony forming units (CFU) per mL along with incubation time and temperature.

Limitations of use: MF hinders the formation of the halo (lecithinase) on the surface of the plate, therefore it is necessary to confirm this test for colonies suspected of being pathogenic S. aureus. The black colonies must be confirmed in Baird Parker medium directly or in BP-RPF medium.

Physical/chemical control

Microbiological control

Membrane filtration / practical range 100 ± 20 CFU, min. 50 CFU (productivity) / 10⁴-10⁶ CFU (selectivity) / ≥ 10³ CFU (specificity).

Aerobiosis. Incubation at 37 ± 1 °C, reading after 24-48 ± 2 h.

Microbiological control according to ISO 11133:2014/Amd 1:2018.

Sterility control

Incubation 48 hours at 30-35 °C and 48 hours at 20-25 °C: NO GROWTH.

Check at 7 days after incubation in same conditions.

• ATLAS R.M. & L.C. PARKS (1993) Handbook of Microbiological Media. CRC Press. London.
• BAIRD-PARKER, A.C. (1962) An improved diagnostic and selective medium for isolating coagulase-positive staphylococci. J. Appl. Bact. 25:12.
• COLIPA (1997) Guidelines on Microbial Quality Management (MQM). Brussels.
• DOWNES, F.P. & K. ITO (2001) Compendium of Methods for the Microbiological Examination of Foods. 4th ed. APHA. Washington. USA.
• EUROPEAN PHARMACOPOEIA (2007) 5th ed. Suppl. 5.6 § 2.6.13 Microbiological examination of non-sterile products. EDQM. Council of Europe. Strasbourg.
• FIL-IDF 60:2001 Standard. Lait et produits à base de lait - Detection des staphylocoques à coagulase positive - Technique du nombre le plus probable. Brussels.
• ISO 5944:2001 Standard. Milk and Milk based products - Detection of coagulase positive staphylococci - MPN Technique. Geneva.
• ISO 6888-1:1999/Amd 2:2018. Standard. Microbiology of food and animal feeding stuffs - Horizontal method for the enumeration of coagulase-positive staphylococci (Staphylococcus aureus and other species) - Part 1 Technique using Baird-Parker Agar medium. Amendment 2: Inclusion of an alternative confirmation test using RPFA stab method.
• ISO 6888-2:1999 Standard. Microbiology of food and animal feeding stuffs - Horizontal method for the enumeration of coagulase-positive staphylococci - Part 1 Technique using rabbit plasma fibrinogen agar medium. Geneva.
• ISO 11133:2014/Amd 1:2018. Microbiology of food, animal feed and water. Preparation, production, storage and performance testing of culture media.
• ISO 22718 Standard (2015). Cosmetics - Microbiology - Detection of Staphylococcus aureus.
• USP 31 - NF 26 (2008) <61> Microbial Limit Tests. US Pharmacopeial Conv. Inc. Rockville. MD. USA.
• ZANGERL, P. & H. ASPERGER (2003) Media used in the detection and enumeration of Staphylococcus aureus. In Handbook.