Mycobacterium abscessus – Molecular Subspeciation and Macrolide Resistance Testing

Testing Indications

Specimen collection is not required for this test.

Effective August 29, 2016, Public Health Ontario laboratory will identify the subspecies of all new patient isolates of Mycobacterium abscessus (M. abscessus ssp abscessus, M. abscessus spp bolletii, and M. abscessus ssp. massilense) using a new molecular testing algorithm, and will identify mutations in two targets that are predictive of macrolide resistance.

Isolate from Mycobacterium abscessus (M. abscessus ssp abscessus, M. abscessus spp bolletii, and M. abscessus ssp. massilense) testing will be used for Mycobacterium abscessus – molecular subspeciation and macrolide resistance testing.

Test Frequency and Turnaround Time (TAT)

The expected TAT is within 7-10 days after the primary culture identification.

Phenotypic drug susceptiblilty testing (DST) is referred to the National Microbiology Laboratory (NML). TAT is approximately four weeks.

Testing will be performed under one or more of the following conditions:

• All new culture positive non-tuberculous mycobacteria isolates are identified by the line-probe assay, the GenoType Mycobacterium CM or AS assays (HAIN Lifescience);
• Where the isolate cannot be identified by the line-probe assay, 16S rRNA sequencing is used for identification;
• Isolates identified as M. abscessus by either line-probe assay or 16S rRNA will be further subspeciated by DNA sequencing methods; additional isolates submitted > 3 months after the initial or previous isolate will be tested but all others will be referred to the first or previous isolate tested result;
• M. abscessus isolates will also be tested for the presence of an intact erm41 gene, and erm(41) sequencing will be performed for M. abscessus ssp abscessus and M. abscessus ssp bolletii to identify non-functional intact erm(41).
• All M. abscessus isolates will be tested by sequencing for mutations in the rrl locus known to confer resistance to macrolides
• M. abscessus ssp abscessus and M. abscessus ssp bolletii isolates where the erm(41) has been identified as non-functional and rrl is not mutated (predictive of macrolide susceptibility) will be sent to the National Microbiology Laboratory (NML) for confirmation by phenotypic drug susceptibility testing (DST), as isolates may still be macrolide resistant due to unknown mechanisms.

Reporting

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

References

LAB-SD-096, Tuberculosis and Mycobacteriology Laboratory Update: Revision of M. abscessus subspeciation algorithm and molecular detection of macrolide resistance