Approximate Formula:
|
Ingredients
|
gm/liter
|
|
Pancreatic digest of casein
|
10.0
|
|
Beef extract
|
5.0
|
|
Yeast extract
|
1.0
|
|
Sodium pyruvate
|
10.0
|
|
Glycine
|
12.0
|
|
Lithium chloride
|
5.0
|
|
Agar
|
15.0
|
|
Final pH 7.0±0.2 at 25℃
|
|
*Adjusted and/or supplemented as required to meet performance criteria.
|
Directions:
Suspend 58.0g of the medium in 950mL of deionized or distilled water. Mix well and heat with frequent agitation. Boil for 1 minute. Dispense and sterilize in the autoclave at 121℃(15 lbs.) for 15 minutes. Cool to 45-50℃and add 10 mL of 1% potassium tellurite solution and 50 mL of sterile egg yolk suspension. Mix gently and pour into Petri dishes. It must not store in the refrigerator exceed 48 hours before to use.
Principle and Interpretation:
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.Pancreatic digest of casein, beef extract and yeast extract provides source of carbon, nitrogen, and other essential growth nutrients. Sodium pyruvate and glycine stimulate the growth of Staphylococcus aureus. Glycine, lithium chloride and potassium tellurite act as selective agents. Egg yolk is the substrate to detect lecithinase production, and, in addition, lipase activity. Staphylococci produce dark gray to black colonies due to tellurite reduction; staphylococci that produce lecithinase break down the egg yolk and cause clear zones around respective colonies. An opaque zone of precipitation may form due to lipase activity.
Appearance:
Dehydrated medium is a free-flowing yellowish powder. The prepared medium is a kind of yellowish opaque gel.
Precautions:
This medium is for laboratory use only. Dried medium which is past shelf life, caking or color variation cannot be used.
Storage conditions and Shelf life:
Baird-Parker Agar must be stored tightly capped in the original container at 5-30°C. The dehydrated medium has a shelf life of 3 years from date of manufacturing. Prepared medium may be stored, out of direct light at 2-8°C.
Quality control:
Inoculate and incubate at 36±1℃for 45-48 hours.
|
Microorganism
|
Strains Number
|
Inoculum (CFU）
|
Recovery
|
Colony colour
|
Lecithinase production(Halos)
|
|
Staphylococcus Aureus
|
ATCC 25923
|
20-200
|
≥70%
|
Black
|
+
|
|
Escherichia coli
|
ATCC 25922
|
102-103
|
≤1%
|
Inhibited
|
-
|
|
Staphylococcus Aureus
|
ATCC 6538
|
20-200
|
≥70%
|
Black
|
+
|
|
Bacillus subtilis
|
ATCC 6633
|
102-103
|
<30%
|
Brown
|
-
|
|
Proteusmirabilis
|
ATCC 12453
|
20-200
|
≥50%
|
Brown-black
|
-
|
|
Staphylococcus epidermidis
|
CMCC(B)26069
|
20-200
|
≥50%
|
Black-grey
|
-
|
Reference :
1. GB4789.28-2013 People's Republic of China food safety national standard food microbiology test medium and reagent quality equirements.
2. Baird-Parker, A.C. 1962. An improved diagnostic and selective medium for isolating coagulase-positive staphylococci.. J. Appl. Bacteriol. 25: 12-19. 3.Wilkie M. E., Almond M. K., Marsh F. P., 1992, British Medical Journal 305:1137-1141. 
Technical Data: