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Susceptibility of Mycobacterium tuberculosis isolates to first line anti-tuberculosis antimicrobials

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Accredited by the Standards Council of Canada to Laboratory no. 594 (ISO/IEC 17025)

Requisition Forms

Reference Details


Susceptibility of Mycobacterium tuberculosis isolates to first line anti- tuberculosis antimicrobials isoniazid, rifampin, ethambutol, and pyrazinamide at critical concentrations using BACTEC™ MGIT™ 960 detection system.

Test Category:
Susceptibility Testing
Mycobacterium tuberculosis
Illnesses and Diseases:
  • Tuberculosis (TB)

Solid or liquid media growth. 

  • For solid media growth, isolated colonies on plated media.  Mycobacterium tuberculosis complex species must show visible growth and be no more than 4 weeks old.
  • For liquid culture, a minimum volume of 4 mL of actively growing culture. 
  • If the culture has inadequate growth, contamination, or mixed Mycobacterium species, the submitted culture will be rejected and a resubmission will be requested.
Collection Method:

Primary cultures should be used when possible.

Specimen Processing, Storage and Shipping:

Ship all cultures at room temperature (DO NOT freeze) for overnight delivery, and prior to Wednesday each week to ensure receipt by Friday.

Transportation of Dangerous Goods:

Shipping of specimens shall be done by a TDG certified individual in accordance with TDG regulations. For additional information regarding classification of specimens for the purposes of shipping, consult either Part 2 Appendix 3 of the TDG Regulations or section 3.6.2 of the IATA Dangerous Goods Regulations as applicable.


Patient Criteria:

Tuberculosis is a reportable disease and susceptibility testing for all cases in Canada is mandatory.

Accompanying Documentation:

Notification of sample submission must be emailed or faxed prior to shipping isolates. Samples should be shipped attention: Melissa Rabb, Head, Reference and Diagnostic Services, NRCM/NML at 204-789-6081/204-789-6038.  A requisition for the NRCM must be completed and signed off by the supervisor/designate of the submitting laboratory and include the source of specimen, patient gender, date of birth, clinical history, submitting laboratory identifier and submitter information.  Please also include isolate characteristics: microscopy, pigmentation, culture characteristics, growth rate/temperature, and identification. 


The test request must be accompanied by preliminary results if testing was performed by the originating laboratory and confirmation of resistance is requested.  Cultures may be rejected if appropriate documentation is incomplete or missing.

Methods and Interpretation of Results:

Susceptibility results for isoniazid, rifampin ethambutol and pyrazinamide will be determined using the BACTEC™ MGIT™ 960 at critical concentrations. The higher isoniazid concentration, moxifloxacin and ofloxacin will be tested if resistance is detected at the critical concentration of isoniazid. Interpretations are made as per the CLSI guidelines (1).

Turnaround Time:

The specimen turnaround time is 30 calendar days from the date of specimen receipt. This TAT includes sample processing and culture growth times. 

Phone #: (204) 789-2136 or (204) 789-6038
Fax: (204) 789-2036
  1. CLSI. Susceptibility Testing of Mycobacteria, Nocardiae, and Other Aerobic Actinomycetes.3rd ed. CLSI standard M24. Wayne, PA: Clinical and Laboratory Standards Institute; 2018.
  2. Inderlied CB and Pfyffer GE.  (2003)  Susceptibility Test Methods: Mycobacteria, p. 1149 – 77.  In Murray PR, Baron EJ, Jorgensen JH, Pfaller MA, and Yolken RH (ed).  Manual of Clinical Microbiology, 8th ed.  American Society for Microbiology, Washington, D.C.
  3. Sabine Rüsch-Gerdes, Gaby E. Pfyffer, Manuel Casal, Maureen Chadwick, and Salman Siddiqi. 2006. Multicenter Laboratory Validation of the BACTEC MGIT 960 Technique for Testing Susceptibilities of Mycobacterium tuberculosis to Classical Second-Line Drugs and Newer Antimicrobials. J. Clin. Microbiol. 44: 688-692.
  4. Annika Krüüner, Malcolm D. Yates, and Francis A. Drobniewski. 2006 Evaluation of MGIT 960-Based Antimicrobial Testing and Determination of Critical Concentrations of First- and Second-Line Antimicrobial Drugs with Drug-Resistant Clinical Strains of Mycobacterium tuberculosis. J. Clin. Microbiol. 44: 811-818.