COBA (COLISTIN OXOLINIC BLOOD) AGAR W/ 5% HORSE BLOOD

Technical Data #1451a / 98.05.12

COBA Agar w/ 5% horse blood is a selective solid medium for the isolation of pathogenic streptococci. Antimicrobial agents, colistin and oxolinic acid, suppress growth of the other bacteria. The addition of blood permits the interpretation of hemolytic activities.

FORMULA
in grams per liter purified filtered water

Casein Peptone

10,0

Beef Extract

5,0

Yeast Extract

5,0

Heart Peptone

3,0

Corn Starch

1,0

Sodium Chloride

5,0

Agar

13,5

Antibiotics

 

Colistin

0,010

Oxolinic Acid

0,005

Defibrinated Horse Blood

50 ml

pH 7,3 +/- 0,2 à 25º 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 2-8º C protected from direct light and dehydrated powder, in a dry place, in tightly-sealed containers at 2-25º 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 42,5 g of dehydrated media in 950 ml of purified filtered water. Heat with frequent agitation and boil for one minute. Sterilize at 121º C for 15 minutes. Cool to 45-50º C. Aseptically add 50 ml of Defibrinated Horse Blood (4526) and 2x5 ml of Colistin-Oxolinic Acid Supplement (8723). Mix gently and dispense into sterile Petri dishes.


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

  1. Directly, inoculate plate as soon as possible with specimen and streak for isolation.
  2. Incubate at 35º C under 5-10% CO2 for 24-48 hours.
  3. Examine for growth and hemolysis activity.


QUALITY CONTROL
Results after 24 hrs at 35ºC W/ CO2

Organisms

ATCC

Growth

Hemolysis

Streptococcus pyogenes

19615

+

bêta

Streptococcus pneumoniae

6305

+

alpha

Enterococcus faecalis

29212

+

 

Escherichia coli

25922

-

 

Pseudomonas aeruginosa

27853

-

 

Staphylococcus aureus

25923

-

 


LIMITATIONS OF METHOD
This medium is only a part of the identification. Other tests may be required.


REFERENCES

  1. Mac Faddin, Jean. F., 1985 Media for Isolation-Cultivation-Identification-Maintenance of Medical Bacteria. Vol. 1. Baltimore, MD.: Williams & Wilkins.
  2. Murray, P.R., A.D. Wold, C.A. Schreck, J.A. Washington II 1976 Effects of selective media and atmosphere of incubation on the isolation of group A streptococci. J. Clin. Microbiol. 4:54-56
  3. , D.N., 1984 Colistin-Oxolinic Acid Blood Agar: a new selective medium for streptococci. J. Clin. Microbiol. 19:3-7


CATALOGUE NUMBERS

Dehydrated media 500 g QB-39-1006
     
Prepared media    
Plates, 100x15 mm 10/pkg 1451
Mono-Plates, 100x15 mm 10/pkg 1451M
     
Defibrinated Horse Blood 50 ml 4526
     
COBA Supplement 10x5 ml 8723

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