MIDDLEBROOK 7H11 SELECTIVE AGAR

Technical Data #39-1265a / 2013.08.18

Middlebrook 7H11 Selective Agar is a solid selective medium used for isolation and cultivation of mycobacteria. Inorganic salts permit mycobacterial growth, glycerol is a source of carbon and energy and malachite green inhibits partially bacterial growth. Cycloheximide, lincomycin and nalidixic acid are the inhibitors.

 


 

FORMULA
in grams per liter purified filtered water

Casein Peptone

1,0

Ammonium Sulfate

0,5

Monopotassium Phosphate

1,5

Disodium Phosphate

1,5

Sodium Citrate

0,4

Magnesium Sulfate

0,05

L-Glutamic Acid

0,5

Ferric Ammonium Citrate

0,04

Pyridoxine

0,001

Biotin

0,0005

Malachite Green

0,001

Agar

15,0

Enrichments

 

OADC Supplement

100 ml

Glycerol

5 ml

Antibiotics

 

Cycloheximide

0,36

Lincomycin

0,002

Nalidixic Acid

0,02

pH 6,9 +/- 0,2 25 C

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


PRECAUTIONS
This medium is for laboratory 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 of dehydrated media in 900 ml of purified filtered water with glycerol. Heat with frequent agitation and boil for one minute. Sterilize at 121 C for 15 minutes. Cool to 45-50 C. Add 100 ml of OADC Supplement (8673) and sterile antibiotics. Mix gently and dispense into sterile Petri dishes.


PROCEDURE
Prior to inoculate, the prepared media should be brought to room temperature. As usual, decontamination, homogenizing, grinding should be done before inoculation..

  1. Incubate inoculated plates at 35C in 5-10% CO2
  2. Read weekly for at least 3 weeks if there is no growth.


QUALITY CONTROL

Expected results after 21 days at 35C 5% CO2

Organisms

ATCC

Growth

Mycobacterium tuberculosis H3Ra

25177

+

Mycobacterium kansasii Group 1

12478

+

Mycobacterium scrofulaceum Group II

19981

+

Mycobacterium intracellulare Group III

13950

+

Mycobacterium fortuitum Group IV

6841

+

Escherichia coli

25922

- or partial


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


REFERENCES

  1. Balows, A., Hausler Jr. W., Herrmann, L.K., Isenberg, D.H., and Shadomy, H.J. 1991 Manual of Clinical Microbiology. 5th ed. American Society for Microbiology. Washington, D.C.
  2. N.C.C.L.S. Quality Assurance for Commercially prepared Microbiological Culture Media. Approved Standard. 1990 Document M22-A.
  3. Sommers, H.M., Mc Clatchy, J.K., Morello, J.A. 1983 Laboratory Diagnosis of the Mycobacteriosis. Cumitech 16. American Society for Microbiology. Washington, D.C.,
  4. Vestal, A.L. 1978 Procedures for the Isolation and Identification of Mycobacterium. DHEW Publication No. CDC 79-8230, CDC Atlanta.


CATALOGUE NUMBERS

Dehydrated media 500 g QB-39-2974
     
Glycerol 100 ml 8467
OADC Supplement 100 ml 8673
     
Prepared media    
Plates, 100X15mm 10/pkg 1265

 


 

 

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