Part III: Culture
diagram 2

NIACIN TEST FOR IDENTIFICATION OF M. tuberculosis
Procedure

Add 1 ml of sterile water  to the culture slant. If growth is confluent, puncture the medium with a Pasteur pipette  to allow contact of the water with the medium

    
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Place the tube horizontally  so the fluid covers the entire surface of the medium

   
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Allow 30 minutes for the extraction of niacin. The extraction time may be longer if the culture has few colonies

   
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Raise the  slants upright for 5 minutes to allow the fluid to drain to the bottom

   
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Remove 0.5ml of  the fluid extract to a clean screwcap tube

  
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Sequentially add 0.5ml of the 4% aniline solution and 0.5ml of 10% cyanogen bromide

   
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Close the tubes  and observe the solution for the formation of a yellow colour (= positive result) within 5 minutes. The yellow colour appears as a ring at the interface of the two reagents, or if the tube is shaken, as a yellow column of liquid

    
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Add 2-3 ml of  4% NaOH to each tube and discard

CONTACTS:

Dr Martie van der Walt
E-mail: vdwalt@mrc.ac.za

Dr Roxanna Rustomjee
E-mail: roxanna.rustomjee@
mrc.ac.za

Prof Valerie Mizrahi
E-mail: mizrahiv@
pathology.wits.ac.za

Prof. Paul van Helden
E-mail: pvh@sun.ac.za

 

Last updated:
22-Jun-2011

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