Cultural Characteristics of Mycobacterium tuberculosis 4.67/5 (18)




Cultural Characteristics of Mycobacterium tuberculosis

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 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 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 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 growth of most other contaminants.
  12. A faster result can now be obtained using 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

References

  1. http://www.meddean.luc.edu/lumen/MedEd/medicine/pulmonar/diseases/tbthc1.htm
  2. https://labtestsonline.org/understanding/analytes/afb-culture/tab/test/
  3. http://textbookofbacteriology.net/tuberculosis.html
  4. http://www.slideshare.net/deshkar/mycobacterium-tuberculosis-seminar
  5. http://textbookofbacteriology.net/tuberculosis.html
  6. http://www.microbiologyinpictures.com/mycobacterium%20tuberculosis.html
  7. https://en.wikipedia.org/wiki/Löwenstein–Jensen_medium
  8. https://microbewiki.kenyon.edu/index.php/Mycobacterium_tuberculosis
  9. http://www.microbeworld.org/component/jlibrary/?view=article&id=6641
  10. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3865090/
  11. http://www.sigmaaldrich.com/technical-documents/articles/microbiology-focus/mycobacteria-identification.html
  12. http://web.uconn.edu/mcbstaff/graf/Student%20presentations/Mtuberculosis/Mtuberculosis.html
  13. http://www.austincc.edu/microbio/2421a/tb

Cultural Characteristics of Mycobacterium tuberculosis

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The Author

Sagar Aryal

Sagar Aryal

I am Sagar Aryal, a passionate Microbiologist and the Scientific Blogger. I did my Master's Degree in Medical Microbiology and currently working as a Lecturer at Department of Microbiology, St. Xavier's College, Kathmandu, Nepal. I am particularly interested in research related to Medical Microbiology and Virology.

2 Comments

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  1. 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?????

  2. 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.

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