Detection and Differentiation of Staphylococcus Aureus on Baird Parker Agar

Jvo Siegrist

Product Manager Microbiology,

AnalytiX Volume 10 Article 4

Baird Parker Agar is used for the isolation and differentiation of coagulase-positive staphylococci in food and pharmaceuticals according to the Baird Parker method.

As a nitrogen source for the organism, casein peptone and meat extract are added to the medium. Yeast extract provides nitrogen as well as other important nutrients like vitamin B12 complex. The medium contains lithium and tellurite, which inhibit most of the contaminating microflora, while glycine and pyruvate enhance Staphylococci growth. Staphylococci can reduce tellurite to telluride, which results in grey to black coloration of the colonies. With the addition of egg yolk, the medium becomes yellow and slightly opaque. A clear halo develops around colonies from coagulase-positive Staphylococcus aureus, and upon further incubation may produce an opaque zone due to an egg yolk–lecithinase reaction (lipolytic activity). Grey-black colonies and a halo on this medium are presumed to be indicative of coagulase-positive staphylococci, as a high correlation between coagulase test and lipophilic activity was found. Staphylococcus aureus and some strains of Staphylococcus saprophyticus (Shaw et al.[5]) may show both of these characteristics, but they are easily distinguished from each other by the different times at which the halo develops.

Baird Parker Agar Base

Baird Parker Agar with Rabbit Plasma Fibrinogen can be used for the detection of coagulase activity. Coagulase-positive organisms appear as grey to black colonies because of the tellurite reduction and as an opaque halo, due to the conversion by coagulase from fibrinogen to fibrin. Only plates with less than 100 characteristic colonies should be counted. The use of this medium eliminates the need for an additional coagulase test.

Media:

• 1.05406
• 79893
• 41712

Supplements:

• Egg yolk tellurite emulsion (Cat. No. 75208)
• RPF Supplement (Rabbit Plasma Fibrinogen Supplement; Cat. No 05939)
• Egg-Yolk Tellurite Emulsion Sterile, 20% 1.03785.0001

Microorganisms for testing performance:

Material No.	Productivity species (all concentrations)	WDCM No.	CFU
CRM06571L-10EA	Staphylococcus aureus	00035	30-120
CRM06571M-10EA	Staphylococcus aureus	00035	500-50,000
VT000357-10EA	Staphylococcus aureus	00035	50,000-150,000
VT000322-10EA	Staphylococcus aureus subsp. aureus	00032	15-80
VT000323-10EA	Staphylococcus aureus subsp. aureus	00032	80-130
VT000324-10EA	Staphylococcus aureus subsp. aureus	00032	130-300
VT000326-10EA	Staphylococcus aureus subsp. aureus	00032	1,000-10,000
VT000327-10EA	Staphylococcus aureus subsp. aureus	00032	50,000-150,000
VT000342-10EA	Staphylococcus aureus subsp. aureus	00034	15-80
VT000343-10EA	Staphylococcus aureus subsp. aureus	00034	80-130
VT000346-10EA	Staphylococcus aureus subsp. aureus	00034	1,000-10,000
VT000347-10EA	Staphylococcus aureus subsp. aureus	00034	50,000-150,000

Material No.	Selectivity species	WDCM No.	CFU
VT000127-10EA	Escherichia coli	00012	50,000-150,000
VT000137-10EA	Escherichia coli	00013	50,000-150,000

Material No.	Specificity species	WDCM No.	CFU
VT001596-10EA	Staphylococcus saprophyticus	00159	1,000-10,000

References

1. BAIRD-PARKER AC. 1962. AN IMPROVED DIAGNOSTIC AND SELECTIVE MEDIUM FOR ISOLATING COAGULASE POSITIVE STAPHYLOCOCCI. 25(1):12-19. https://doi.org/10.1111/j.1365-2672.1962.tb01113.x

2. Köhler W. 1975. E. H. Lennette, E. H. Spaulding and J. P. Truant (Editors), Manual of Clinical Microbiology (2nd Edition). 970 S., 241 Abb., 189 Tab., 1 Tafel. Washington 1974: American Society for Microbiology. $ 15.00. Z Allg Mikrobiol. 15(4):303-303. https://doi.org/10.1002/jobm.19750150418

3. Schau H. 1986. J. F. MacFaddin, Media for Isolation - Cultivation - Identification - Maintenance of Medical Bacteria, Volume I. XI + 929 S., 163 Abb., 94 Tab. Baltimore, London 1985. Williams and Wilkins. $ 90.00. ISBN: 0-683-05316-7. J Basic Microbiol. 26(4):240-240. https://doi.org/10.1002/jobm.3620260414

4. Niskanen A, Aalto M. 1978. Comparison of selective media for coagulase-positive enterotoxigenic Staphylococcus aureus.. 35(6):1233-1236. https://doi.org/10.1128/aem.35.6.1233-1236.1978

5. Shaw C, Stitt JM, Cowan ST. 1951. Staphylococci and their Classification. Journal of General Microbiology. 5(5):1010-1023. https://doi.org/10.1099/00221287-5-5-1010

6. ISO 6888-1:1999; Microbiology of food and animal feeding stuffs – Horizontal method for the enumeration of coagulasepositive staphylococci (Staphylococcus aureus and other species) – Part 1: Technique using Baird-Parker agar medium.. [Internet]. Available from: https://www.iso.org/standard/23036

7. ISO 6888-2:1999; Microbiology of food and animal feeding stuffs – Horizontal method for the enumeration of coagulase-positive staphylococci (Staphylococcus aureus and other species) – Part 2: Technique using rabbit plasma fibrinogen agar medium.. [Internet]. Available from: https://www.iso.org/standard/25571.html

8. ISO 6888-3:2003; Microbiology of food and animal feeding stuffs – Horizontal method for the enumeration of coagulasepositive staphylococci (Staphylococcus aureus and other species) – Part 3: Detection and MPN technique for low numbers.. [Internet]. Available from: https://www.iso.org/standard/33147.html