for isolation & enumeration of coagulase positive Staphylococci from foods & pharma products
BAIRD PARKER AGAR BASE is used for the isolation and enumeration of coagulase positive Staphylococci. Casein enzymatic hydrolysate, Beef extract are the source of carbon and nitrogen. Yeast extract provides vitamins (B-complex) which helps in stimulating bacterial growth. The selectivity of the medium is maintained by the addition of Lithium chloride and 3.5 % of Potassium Tellurite solution. Both are helpful in suppressing the growth of other organism except Staphylococci sp.Lithium chloride and potassium tellurite inhibit the accompanying flora. Glycine and Sodium pyruvate stimulate the growth of Staphylococci. Staphylococci that contain lecithinase break down the egg yolk and form clear zones around the colonies. Black colonies are formed due to reduction of the Potassium tellurite to tellurium. The plates should be dry before inoculation (the drying can be done by incubating at 35 ± 2°C for approximately 10 minutes before use). Prepare the sample in an adequate solution, dilute it and place from 0.1 ml to 1.0 ml of the appropriate dilution in the plates. Spread the inoculum over the entire surface. Typical S. aureus colonies are black, shiny, convex and surrounded by a clear zone of approximately 2 - 5 mm in diameter. Some other micro-organisms, which occasionally grow on this medium, are micrococci that form small dark or black colonies, yeasts that form white colonies and some species of Bacillus that form dark brown matte colonies.