UREA CHRISTENSEN AGAR

Technical Data #2128a / 2013.06.23

Urea Christensen Agar is a solid differential medium by microorganism ability to split urea, forming two molecules of ammonia by the action of enzyme urease with alkaline result. Proteus sp. give faster positive results than other microorganisms.

 


 

FORMULA
in grams per liter purified filtered water

Gelatin Peptone

1,0

Dextrose

1,0

Sodium Chloride

5,0

Potassium Phosphate, monobasic

2,0

Urea

20,0

Phenol Red

0,012

Agar

15,0

pH 6,8 +/- 0,2 25 C

This approximate formula may be adjusted and/or enriched to obtain best results.


PRECAUTIONS
This medium is for IN VITRO diagnostic use only.


STORAGE
Store prepared media at 2-8 C protected from direct light and dehydrated powder, in a dry place, in tightly-sealed containers at 2-8 C.


SIGN OF DETERIORATION
Media should not be used if the expiry date has passed. Prepared media should not be used if there are signs of contamination or deterioration (shrinking, cracking, evaporation or discoloration). Do not use dehydrated media if it is caked.


DIRECTIONS
Suspend 15 g of bacteriological agar in 900 ml of purified filtered water. Heat with frequent agitation and boil for one minute. Sterilize at 121 C for 15 minutes. Cool to 45-50 C and aseptically, add 10x10 ml of Concentrated Urea (2864). Mix gently and dispense into sterile culture tubes.


PROCEDURE
Prior to inoculate, the prepared media should be brought to room temperature.

  1. Inoculate tubes with an overnight growth. Do not stab the butt.
  2. Incubate at 35 C for up to 6 days with loosened caps.
  3. Examine for urease activity every day.


QUALITY CONTROL

Results after 24 hrs at 35C

Organisms

ATCC

Color

Proteus mirabilis

12453

pink-reddish

Escherichia coli

25922

no change


LIMITATIONS OF METHOD
Some organisms may show a positive urease action after few days only. This medium is only a part of the identification. Other tests may be required.


REFERENCES

  1. Christensen, W.B., 1946 Urea decomposition as a means of differentiating Proteus and paracolon cultures from each other and from Salmonella and Shigella types. J. Bacteriol. 52:461-466
  2. Lennette, E.H., Ballows, A., Hausler, W.J.Jr., and Shadomy, H.J. Manual of Clinical Microbiology. 4th ed. 1985 Washington D.C.: American Society for Microbiology.
  3. Mac Faddin, Jean. F., 1985 Media for Isolation-Cultivation-Identification-Maintenance of Medical Bacteria. Vol. 1. Baltimore, MD.: Williams & Wilkins.


CATALOGUE NUMBERS

Dehydrated media 500 g QB-39-5306
Agar 500 g QB-39-0221
     
Concentrated Urea,10 ml 10/pkg 2864
     
Prepared media    
Tubes, 16X125 mm 10/pkg 2128
Tubes, 13x100 mm 100/box 2454-H

 


 

 

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