MACKONKEY AGAR

MACKONKEY AGAR
A.
COMPOSITION
se peptone (meat and casein) :3 gm
Lactose monohydrate :10 gm
Bile salts :1.5 gm
Sodium chloride : 5 gm
Neutral red : 0.03 gm
Crystal Violet :0.001 gm
Peptone (Pancreatic digest of gelatin) : 17 gm
Proteo
Agar :13.5 gmH
C.
PRINCIPLE
1.MacConkey agar is used for the isolation of gram-negative enteric bacteria and the differentiation of lactose fermenting from lactose non-fermenting gram-negative bacteria.
2. Pancreatic digest of gelatin and peptones (meat and casein) provide the essential nutrients, vitamins and nitrogenous factors required for growth of microorganisms.
3.Lactose monohydrate is the fermentable source of carbohydrate. The selective action of this medium is attributed to crystal violet and bile salts, which are inhibitory to most species of gram-positive bacteria.
4. Sodium chloride maintains the osmotic balance in the medium. Neutral red is a pH indicator that turns red at a pH below 6.8 and is colorless at any pH greater than 6.8. Agar is the solidifying agent.
B.
PREPERATION
STEP1
Suspend 49.53 grams of dehydrated medium in 1000 ml purified/distilled water.
STEP2
Heat to boiling to dissolve the medium completely.ic
STEP3
STEP4
Cool to 45-50°C.ic
STEP 5
Mix well before pouring into sterile Petri plates.ic
D.
USES
Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes.c
MacConkey agar is used for the isolation of gram-negative enteric bacteria.
It is used in the differentiation of lactose fermenting from lactose non-fermenting gram-negative bacteria.
It is used for the isolation of coliforms and intestinal pathogens in water, dairy products and biological specimens.opic
Lactose non-fermenting strains, such as Shigella and Salmonella are colourless and transparent and typically do not alter appearance of the medium. Yersinia enterocolitica may appear as small, non-lactose fermenting colonies after incubation at room temperature
Lactose fermenting strains grow as red or pink and may be surrounded by a zone of acid precipitated bile. The red colour is due to production of acid from lactose, absorption of neutral red and a subsequent colour change of the dye when the pH of medium falls below 6.8.
RESULT
Science Prof Online (SPO): MacConkey Agar
Bacteriological Analytical Manual, 8th Edition, Revision A, 1998.
Collin County Community College District.
Microbe Online
Wikipedia
REFERENCES
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