MIDDLEBROOK 7H11 AGAR, MITCHISON MODIFIED

Technical Data #2851a / 2013.11.01

The selective Mitchison Modified 7H11 Agar is used for isolation of Mycobacterium sp. from contaminated specimens. The addition of 0.1% casein peptone enhances Mycobacterium growth more than on Middlebrook 7H10. The antibiotics inhibit bacteria Gram negative and Gram positive and fungi.

 


 

FORMULA
in grams per liter purified filtered water

Casein Peptone

1,0

Ammonium Sulfate

0,5

Glutamic Acid

0,5

Sodium Citrate

0,4

Potassium Phosphate, mono-basic

1,5

Sodium Phosphate, dibasic

1,5

Magnesium Sulfate

0,05

Ferric Ammonium Citrate

0,04

Biotin

0,0005

Pyridoxine

0,001

Malachite Green

0,001

Agar

15,0

Glycerol

5,0 ml

OADC Supplement

 

Albumin Fraction V

5,0 g

Dextrose

2,0

Sodium Chloride

0,85

Catalase

0,004

Antibiotics

 

Carbenicilline

0,05

Trimethoprim

0,02

Amphotericin B

0,01

Polymyxin B

200,000 units

pH 6,6 +/- 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 2-8° C protected from direct light and dehydrated powder, in a dry place, in tightly-sealed containers at 2-25° 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 21 g in 900 ml of purified water containing 5 ml of Glycerol. Heat with frequent agitation and boil for one minute. Sterilize at 121° C for 15 minutes. Cool to 45-50° C and, aseptically, add 100 mL of OADC Supplement(8673) and the antibiotics. Dispense into sterile culture tubes and let solidify in slant position.


PROCEDURE
Bring prepared medium at room temperature before inoculation. As usual, decontamination, homogenizing, grinding should be done before inoculation.

  1. Inoculate tubes with specimen as soon as possible.
  2. Incubate inoculated tubes with loosened caps, at 35° C in 5-10% CO2.
  3. Read weekly for a maximum of 3 months.


QUALITY CONTROL

Expected results after 21 days at 35ºC 5-10% CO2

Organisms

ATCC

GROWTH

Mycobacterium tuberculosis H3Ra

25177

+

Mycobacterium kansasii Group 1

12478

+

Mycobacterium scrofulaceum Group II

19981

+

Mycobacterium fortuitum Group IV

6841

+

Escherichia coli

25922

- (partial)

Staphylococcus aureus

25923

- (partial)


LIMITATIONS OF METHOD
This is only a part of the identification. Others tests may be required. Mitchison 7H11 Agar should be incubated at 35° C under 5-10% CO2 conditions.


REFERENCES

  1. Middlebrook G., and M.L. Cohn Am. J. Publ. Health, 48 844 Bacteriology of tuberculosis methods. 1958
  2. Mitchison D.A. et al. J. Med. Microbiol., 5:165-175, 1972


CATALOGUE NUMBERS

Dehydrated media 500 grams QB-39-2974
     
Glycerol 500 grams QB-39-9012
     
OADC Supplement 100 ml 8673
     
Prepared media    
tubes 20x125 mm, slant 10/pkg 2851
tubes 20x125 mm, slant 100/box 2161-H

 


 

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