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Linked Node

  • Identification and Susceptibility Methods for MTB/Isolated Mycobacteria

    Learning Objectives

    List methods to identify MGIT growth as MTB that differentiates it from other contaminants

    • Immunochromatographic Test SD Bioline Assay: Participants will acquire knowledge about the SD Bioline assay for rapid identification of MTB.
    • Biochemical Tests for MTB: Participants will gain understanding of various biochemical tests to confirm MTB identification, including:
      • Niacin Production Test: Knowledge about the niacin production test to differentiate MTB from other mycobacteria.
      • Nitrate Reduction Test: Understanding the nitrate reduction test to identify MTB based on its ability to reduce nitrate to nitrite.
      • Catalase Peroxidase Test: Insight into the catalase peroxidase test to assess enzyme activity specific to MTB.
    • SIRE Susceptibility Testing: Participants will learn about SIRE (Streptomycin, Isoniazid, Rifampicin, and Ethambutol) susceptibility testing to determine drug resistance.
    • Pyrazinamide (PZA) Susceptibility Testing: Knowledge about susceptibility testing for Pyrazinamide to assess MTB resistance.
    • Susceptibility of MTB to p-Nitrobenzoic Acid (PNB): Understanding how to test MTB isolates for susceptibility to p-nitrobenzoic acid and interpret the findings.
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Content

The following observations can make tentative identification:

  1.   Rate of growth: Generally, M. tuberculosis, M. bovis and, to some extent, M. Kansasii are slow growers and take a longer time to turn positive in an MGIT tube as compared to other non tuberculous mycobacteria (NTM). 

  2.   Nature of turbidity: In liquid medium, M. tuberculosis appears as granular or flaky growth, while most NTM form uniform slight turbidity (except M. kansasii).

  3.   Smear examination: M. tuberculosis forms typical clumps and serpentine cords, while other mycobacteria appear as loose, smaller clumps and cording single cells. M. kansasii may be difficult to differentiate as it is morphologically closer to M. tuberculosis.

  4.   Lateral flow immunochromatography (Capilia TB Test): Used to differentiate M. tuberculosis from NTM. 

  5.  Other methods: For complete speciation, other biochemical tests can be used.

    Resource

Mycobacteriology Laboratory Manual 

Assessment

Question 1

Answer 1

Answer 2

Answer 3

Answer 4

Correct Answer

Correct Explanation

Page id

Part of Pre-Test

Part of Post-Test

The majority of mycobacterial species grow well at 37°C ± 1ºC.

True

False

 

 

True

Most mycobacterial species grow well at 37°C ± 1ºC; however, some may require temperatures other than 37°C.

 

Yes

Yes

Question 2

 

 

 

 

 

 

 

 

 

The reagents for decontamination can be used, which were prepared one month back.

True

False

 

 

False

It is better to use freshly prepared reagents.

 

Yes

Yes

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