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

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.

Solid or liquid media growth.

• For solid media growth, isolated colonies on plated media are preferred. 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 is preferred.

• If there is inadequate growth, or there is contamination, submitted cultures will be rejected and a resubmission will be requested.

N/A

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

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.

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

Requisitions must be faxed prior to shipping isolates to NRCM - attention Joyce Wolfe, Program Manager, NRCM/NML at 204-789-2036. 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. Also include isolate characteristics: microscopy, pigmentation, culture characteristics, growth rate/temperature, and identification.

Must be accompanied by preliminary results if testing was performed by the originating laboratory. Cultures may also be rejected if appropriate documentation is incomplete or missing.

Susceptibility results for isoniazid, rifampin ethambutol and pyrazinamide will be determined using the BACTECTM MGITTM 960 using critical concentrations recommended by the CLSI (1).

It can take 1-2 weeks for appropriate culture growth before the test can be set up. This can add up to 2 weeks to the test turnaround time of 14 calendar days from date of test set up. A specimen turnaround time of 30 calendar days from the date of specimen receipt includes sample processing and culture growth times.

1. CLSI (2011) Susceptibility Testing of Mycobacteria, Nocardiae, and Other Aerobic Actinomycetes; Approved Standard. M24-A2. Vol. 31, No. 5

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