Diagnosis of Mycobacterium

Mycobacteria are mandatory aerobic or microaerophilic bacilli, acidophostal, gram-positive, and bar-shaped. Mycobacteria are mandatory intracellular bacteria that grow within monocytes and macrophages.

1) Mycobacterium genus

The Mycobacterium family contains only the genus Mycobacterium, which is a gram-positive aerobic basilar with a genomic content of GC of 70-62%.Mycobacterium in the cell wall itself contains mycological acid of the type IV chetotype.

Nevertheless, the coloring of Nelson is one of the most famous and yet simplest methods for early identification of mycobacteria. It is believed that many slow-growing species are related to disease in humans or animals. Unlike slow-growing species, most sparse species are less susceptible to human disease and are considered as opportunistic pathogens.

2) Mycobacterium tuberculosis

Mycobacterium tuberculosis Tuberculosis is a member of a collection that has at least 9 species:

  • tuberculosis sensu stricto, M. africanum, M. canetti, M. bovis, M. caprae,
  • microti, M. pinnipedii, M. mungi and M. orygis.

3) Non-TB Mycobacteria (NTM)

Non-TB mycobacteria are a large group of mycobacteria, and they are called differently: Mycoplasma, unclassified, tuberculoid and peripheral mycobacterium. These bacteria are widely found in the environment and through this can be transmitted to humans.

There is no evidence that humans or humans have human to human transmission of mycobacteria.

diagnosis of mycobacterium

diagnosis of mycobacterium

4) Principles and diagnosis of mycobacterial diseases

Principles of the isolation of mycobacterium are based on the isolation of the causative agents of the patient’s specimen, such as: phlegm, urine, bone tissue, body fluids, blood which may be associated with clinical signs, suspected radiographic findings, individual immune status, and history of the disease.

Tuberculosis diagnosis is based on clinical symptoms, laboratory results, microbiology, pathology, tuberculin skin test and radiography.

1-4) Identification of Mycobacterium Species

To identify and identify mycobacteria, a range of the simplest laboratory tests are designed to the most complex molecular and non-molecular methods, each of which has many strengths and weaknesses. Due to the nature of slow growth of mycobacteria and the very close proximity of a number of species to each other, the differentiation of mycobacterium species has their own complexity.

2-4) Common Microbiological Tests

When a species of mycobacterium is isolated from clinical specimens, a definitive diagnosis should be identified and, if necessary, epidemiologically, such as an examination of how to transfer from one patient to another, a new infection, or a recurrence of the disease. To be placed.

3-4) Microscopic examination (direct)

Microscopic or direct microscopic or direct microscopic or direct microscopic examination is the most important method for diagnosing and controlling the treatment process. The easiest way is to evaluate the patient’s infected specimens. Extending the sample, then staining.

4-4) cultivate

Cultivation is s golden standard for the detection of mycobacterium. Use of both solid and liquid media is used to cultivate mycobacterium. Generally, there are three types of media for mycobacterium:

1- Agar-based environments, such as Mid-Brok 7H11 or 7H10

2- Ampoule Moisture medium such as Mid-Broken 7H9 or 7H12 or Dubbine Tween Albumin

5-4) alternative culture media

While Leviin-Stein Johnson’s culture media are the most popular culture medium for mycobacteria, the International Tobacco Association has recommended several alternatives to be tested.

6-4) Solid culture medium


  • Egg-based – Petragnani mediumand Dorset medium
  • Middlebrook 7H10 agar
  • Middlebrook 7H11 agar
  • Blood-based – Tarshis medium
  • Serum-based – Loeffler medium
  • Potato-based – Pawlowsky medium

7-4) Liquid culture media

  • Dubos’ medium
  • Middlebrook 7H9 broth
  • Proskauer and Beck’s medium
  • Juice’s medium
  • Sauton’s medium

Disadvantages of Mycobacterium culture


  • The cultivation of bacteria for testing tuberculosis is much more complicated and more expensive than smear production from sputum and its microscopic observation. This is because bacterial culture requires special laboratory equipment and facilities. Tests and diagnosis of Mycobacterium tuberculosis by cultivation can last for weeks due to the slow growth of tuberculosis.
  • On average, the result of a reliable test for the cultivation of tuberculosis bacteria takes 4 weeks using common methods. Also, the duration of another 4 to 6 weeks is required to obtain drug resistance results. One of the ways to reduce time is to use liquid culture media. There are now automatic devices for bacterial culture.


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