Mycobacterium – TB Susceptibility Testing

NOTICE: Expected delay in Mycobacterium tuberculosis complex (MTBC) bedaquiline, clofazimine, and levofloxacin susceptibility testing Turnaround Time (TAT)

Due to reagent supply issues at the National Reference Centre for Mycobacteriology (NRCM), bedaquiline, clofazimine, and levofloxacin phenotypic drug susceptibility testing for MTBC performed at the NRCM is currently delayed and is expected to return to normal by early April. The NRCM will offer antimicrobial resistance prediction by whole genome sequencing and proceed with phenotypic testing once reagents are received. Please contact PHO’s Laboratory Customer Service for urgent requests.

Consistent with O. Reg. 671/92 of the French Language Services Act, laboratory testing information on this page is only available in English because it is scientific or technical in nature and is for use only by qualified health care providers and not by members of the public.

*Uncontrolled print copy. Valid only on day of print: 01 May 2024.

Specimen Collection and Handling

Specimen Requirements

Test Requested	Required Requisition(s)	Specimen Type	Minimum Volume	Collection Kit
Mycobacterium – TB Susceptibility testing	Reference Bacteriology Requisition	M. tuberculosis complex culture	N/A	N/A

Submission and Collection Notes

Submit viable growth of a viable M. tuberculosis complex culture on solid or in liquid Mycobacterium culture medium.

Contaminated or non-viable cultures will not be tested.

Storage and Transport

Label the specimen container with the patient’s full name, date of collection and one other unique identifier such as the patient’s date of birth or Health Card Number. Failure to provide this information may result in rejection or testing delay.

Place specimen container in the biohazard bag and seal bag, and insert the completed requisition in the pocket on the outside of the sealed biohazard bag.

Special Instructions

Continue to incubate if transport is delayed more than one hour. Specimens should be transferred to the lab ASAP where possible.

Requisitions and Kit Ordering

Test Frequency and Turnaround Time (TAT)

Mycobacterium tuberculosis complex susceptibility testing is performed daily from Monday to Friday.

Turnaround time for 1st line MTBC susceptibility testing is up to 12 days from the date of the culture report.

Turnaround time for reporting 2nd line MTBC susceptibility results is up to 12 days after the 1st line test results are reported.

Test Methods

Susceptibility testing for MTBC is performed using the BACTEC MGIT 960 method, Becton Dickinson, MD. For information on the BACTEC 960 see BACTEC MGIT 960 User’s manual.

The first culture of MTBC isolated from a patient is routinely tested for susceptibility to each of the four first line anti- tuberculosis drugs isoniazid (INH), rifampin (RIF), ethambutol (EMB) and pyrazinamide (PZA). Susceptibility testing to the first line drugs is repeated at three months if cultures are still positive.

MTBC isolates resistant to INH at 0.1mg/L are also tested at 0.4 mg/L and Moxifloxacin and is also tested. Any test that shows resistance to rifampin or any two of the first line drugs is further tested for susceptibility to second line drugs.

In the case of resistance to PZA, testing to determine whether the strain is M.bovis or M.bovis BCG is automatically performed at the TB and Mycobacteriology Laboratory in Toronto since these species are resistant to PZA.

Reporting

Results are reported to the ordering physician or health care provider as indicated on the requisition.

Specimens that are positive for Mycobacterium tuberculosis complex are reported to the Medical Officer of Health as per Health Protection and Promotion Act.