Cultural Characteristics of Mycobacterium tuberculosis

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Last Updated on January 3, 2020 by Sagar Aryal

Cultural Characteristics of Mycobacterium tuberculosis

  1. Culture is the gold standard for laboratory confirmation of Tuberculosis.
  2. Growing bacteria are required to perform drug-susceptibility testing and genotyping.

In the Lowenstein-Jensen (LJ) medium

  1. It is an egg-based medium and growth is quite slow.
  2. It takes 6-8 weeks to get visual colonies on this type of media.
  3. Colonies are non-pigmented, dry, rough, raised, irregular with a wrinkled surface
  4. They are creamy-white initially, becoming yellowish or buff-colored on further incubation.
  5. Growth is eugonic (grows more luxuriantly in culture).
  6. Optimum temperature is 35-37°C and the optimum pH is 6.4 to 7.
  7. It is an obligate aerobe.
  8. Increased carbon dioxide (5-10%) enhances the growth of Mycobacterium tuberculosis.
  9. 5% Glycerol also stimulates the growth.
  10. LJ media contain inhibitors to keep contaminants from out-growing Mycobacterium tuberculosis.
  11. The green color of the medium is due to the presence of malachite green which is one of the selective agents to prevent the growth of most other contaminants.
  12. A faster result can now be obtained using the Middlebrook medium or BACTEC.

Other Culture Media used for Mycobacterium tuberculosis

Solid media

  1. Egg-based – Petragnini medium and Dorset medium
  2. Middlebrook 7H10 Agar
  3. Middlebrook 7H11 Agar
  4. Blood-based – Tarshis medium
  5. Serum based – Loeffler medium
  6. Potato based – Pawlowsky medium

Liquid media

  1. Dubos’ medium
  2. Middlebrook 7H9 Broth
  3. Proskauer and Beck’s medium
  4. Sula’s medium
  5. Sauton’s medium



Cultural Characteristics of Mycobacterium tuberculosis

6 thoughts on “Cultural Characteristics of Mycobacterium tuberculosis”

  1. gold standard does not mean it is crucial to do for each cases. In such case other rapid tests can be done , such as PCR, Gene Expert etc.

  2. As it takes 6 to 8 weeks to grow on LJ medium, and if the patient’s health is getting worse and cannot wait upto 8 weeks, then what will be the gold standard diagnostic test?????


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