Mycobacterium – NTM Susceptibility Testing

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.

Background
This page provides antimicrobial susceptibility testing information for non-tuberculous mycobacteria (NTM) at Public Health Ontario (PHO). NTM are opportunistic pathogens that can be causative agent(s) of various disease presentations including respiratory, cutaneous, and disseminated infections.

For information regarding other testing options, refer to the following PHO webpages:

Updates

Addition of the Request for Susceptibility Testing of Non-tuberculous Mycobacteria (NTM) form required by the National Reference Centre for Mycobacteriology for all susceptibility testing requests.

*Uncontrolled print copy. Valid only on day of print: 05 March 2026.

Testing Indications

The physician must contact PHO Laboratory Customer Service Centre to obtain test approval from a PHO Microbiologist or designate before submitting the specimen and requisition. Test requests for NTM susceptibility written on the requisition will not be accepted without prior approval.

Approval is based on meeting clinical disease and/or microbiological criteria:
Pulmonary or systemic symptoms and nodular or cavitary opacities on chest X-ray or CT scan showing bronchiectasis with multiple small nodules (for NTM pulmonary disease) and
Positive culture results from at least 2 separate expectorated sputum specimens, at least one bronchial wash or lavage, or at least one sterile source.
Treatment is planned, ongoing, or antimicrobial susceptibility results are required to modify therapy.

Specimen Collection and Handling

Specimen Requirements

Test Requested	Required Requisition(s)	Specimen Type	Minimum Volume	Collection Kit
Mycobacterium – NTM Susceptibility Testing	Reference Bacteriology Requisition	Referred NTM cultures	N/A	Appropriate solid or liquid media to support growth of acid-fast bacilli

Submission and Collection Notes

Complete all fields of the requisition form, including:

Test(s) requests and indications for testing
Patient setting/population/source
Specimen information
Patient information
Submitter/Health Care Provider (HCP) Information

NTM susceptibility testing is performed once per year unless a different clinically significant NTM is isolated or in settings of treatment failure.

Clinical history, reason for request, treatment history, duration of antimicrobials used (if applicable), and if clofazimine results are required on the report must be provided using the Request for Susceptibility Testing of Non-tuberculous Mycobacteria (NTM) form or during consultation with PHO’s Microbiologist or the laboratory’s Operational Lead. The form may be submitted by fax to PHO Laboratory Customer Service Centre at 416-235-6552 or with a referred culture in the pocket on the outside of the sealed biohazard bag.

NTM susceptibility testing requests must be made within 3 months of culture identification.

Approval for NTM susceptibility testing must be given prior to specimen submission for referred NTM cultures.

Submit viable growth of NTM culture on solid or in liquid Mycobacterium culture medium. A completed Request for Susceptibility Testing of NTM form must be submitted together with the referred culture if NTM identification and susceptibility testing is indicated on the requisition.

NTM susceptibility testing is not performed on M. gordonae and M. paragordonae isolates as these species are generally considered clinically insignificant.

Storage and Transport

Label the culture 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 delay in testing.

Before packaging, place culture container(s) in a biohazard bag and insert the completed requisition and Request for Susceptibility Testing of NTM form in the pocket on the outside of the sealed biohazard bag. Continue to incubate if transport is delayed more than one hour. All clinical specimens should be shipped to PHO as soon as possible and in accordance to the Transportation of Dangerous Good Act.

Requisitions and Kit Ordering

Test Frequency and Turnaround Time (TAT)

NTM susceptibility testing is referred out to the National Reference Centre for Mycobacteriology (NRCM). The time required to obtain sufficient growth for shipment varies by species: slowly growing mycobacteria may require 3-4 weeks, whereas rapidly growing mycobacteria may produce adequate growth within 1-2 weeks.

Turnaround time (TAT) is up to 45 calendar days from date of sample receipt at the NRCM.

Test Methods

If testing is approved by PHO, a subculture will be prepared from the original isolate. Once adequate growth has been attained, the subculture will be shipped to the National Reference Center for Mycobacteriology (NRCM).

NTM susceptibility testing is performed by broth microdilution at the NRCM. Slowly growing mycobacteria are tested using SLOMYCO2 Sensititre^TM Panels. Rapidly growing mycobacteria are tested using RAPMYCO2 Sensititre^TM Panels. RAPMYCO2 Sensititre^TM Panels with a sensitive clarithromycin result at day 3 will be incubated for up to 14 days to identify the presence of inducible macrolide resistance.

Antimicrobial agents included in the SLOMYCO2 Sensititre^TM Panel include amikacin, ciprofloxacin, clarithromycin, clofazimine (request for result must be indicated), doxycycline, linezolid, minocycline, moxifloxacin, rifabutin, rifampin, streptomycin, trimethoprim/sulfamethoxazole.
Antimicrobial agents included in the RAPMYCO2 Sensititre^TM Panel include amikacin, cefoxitin, ciprofloxacin, clarithromycin, clofazimine (request for result must be indicated), doxycycline, imipenem, linezolid, moxifloxacin, tigecycline, and trimethoprim/sulfamethoxazole.

For susceptibility testing of antimicrobial agents not part of the SLOMYCO2 or RAPMYCO2 Sensititre^TM Panels, the physician must contact PHO’s Microbiologist, the laboratory’s Operational Lead, or PHO Laboratory Customer Service Centre for consultation and test approval.

Interpretation

Interpretations for minimum inhibitory concentration (MIC) values are provided as per the CLSI guidelines¹ when available. For species with no breakpoints and interpretation categories, MIC values for antimicrobial agents will be provided. Refer to the National Reference Centre for Mycobacteriology – Slowly Growing Broth Microdilution MIC Panels for NTM and Rapidly Growing Broth Microdilution MIC Panels for NTM for further information.

Reporting

Results are reported to the physician, authorized health care provider (General O. Reg 45/22, s.18) or submitter as indicated on the requisition.

References

CLSI. Performance Standards for Susceptibility Testing of Mycobacteria, Nocardia spp., and Other Aerobic Actinomycetes. 2nd edition. CLSI supplement M24S. Clinical and Laboratory Standards Institute; 2023.