Baird-Parker medium

Presumptive test The various types of media used for detecting Staphylococcus aureus are presented in Table 4.15. Water samples (100 mL) are filtered through a 0.45 xm membrane. The membrane is then placed on Baird-Parker medium and incubated at 35-37°C + 1°C for 24r-48 h. The medium contains pyruvate and glycine that selectively stimulate the growth of Staphylococcus spp. Colonies measuring 1-5 mm in diameter that are shining, black, convex, and surrounded by a clear zone suggest the presence of S. aureus [2]. 

Presumptive Test Baird-Parker medium Colonies surrounded 35°C-37°C 1°C for 24r-i8 h [2,65]... 

In media selective for enterobacteria a surface-active agent is the main selector, whereas in staphylococcal medium sodium and lithium chlorides are the selectors staphylococci are tolerant of salt concentrations to around 7.5%. Mannitol salt, Baird-Parker (BP) and Vogel-Johnson (VJ) media are three examples of selective staphyloccocal media. Beside salt concentration the other principles are the use of a selective carbon source, mannitol or sodium pyruvate together with a buffer plus acid-base indicator for visualizing metabolic activity and, by inference, growth. BP medium also contains egg yolk the lecithin (phospholipid) in this is hydrolysed by staphylococcal (esterase) activity so that organisms are surrounded by a cleared zone in the otherwise opaque medium. The United States Pharmacopeia (1990) includes a test for staphylococci in pharmaceutical products, whereas the British Pharmacopoeia (1993) does not. 

Baird-Parker (BP) medium Shiny, black convex colonies (1-5 mm in diameter) surrounded by clear zone 35°C for 48 + 2 h [2]... 

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