Molecular Detection of Drug Resistance (MDDR) for Mycobacterium tuberculosis complex
Molecular-based antimicrobial susceptibility testing (AST) is a rapid DNA sequencing based platform aimed at the detection of the presence of Mycobacterium tuberculosis complex within a processed clinical specimen (NAAT) as well as the detection of genetic markers that may indicate drug resistance (MDDR) within Mycobacterium tuberculosis complex (MTBC). Results are available in hours as compared to weeks for conventional antimicrobial susceptibility testing. Culture based drug susceptibility testing remains the gold standard for determining drug resistance within a MTBC isolate and will continue to be conducted in parallel with molecular methods.
Rapid detection of M. tuberculosis complex specific marker (IS6110) and molecular-based antimicrobial susceptibility testing using DNA pyrosequencing.
Molecular and growth-based susceptibility testing are automatically performed on MTBC isolated from each patient.
Submit isolates using the tuberculosis (TB) Category A carrier provided by the MSPHL in accordance with the Infectious Substance, Category A shipping guidelines.
Acceptable Specimen Type(s)
Submit a slant (L-J, Middlebrook, or Mitchison) or liquid broth culture (MGIT, VersaTREK, or MP).
Mixed or non-viable MTBC organism is acceptable; however, growth-based AST may not be available.
Test Request Form(s)
- NAAT (IS610 Marker)
- MDDR (Rifampin Interpretation, Isoniazid Interpretation, Fluoroquinolones Interpretation, Amikacin, Kanamycin, Capreomycin Interpretation)
- Mutation Detected or Not Detected
- Indicates Susceptibility or Resistance or Clinical Significance Unknown
No name or patient identifier on specimen
Specimen leaked during transport to the laboratory
Results are reported the same day of receipt for known TB isolates
An isolate with mutations present confirming multidrug-resistant TB (MDR-TB) or extensively drug resistant TB (XDR-TB) will automatically be submitted to the CDC for confirmation and second-line antimicrobial susceptibility testing.
Testing will automatically be repeated, or upon request, on MTBC isolated from patients who has been on three months of antitubercular therapy to determine if the patient has developed resistance.
The Association of State and Territorial Health Officials (ASTHO) recognized the use of a universal laboratory screening test for multidrug-resistant tuberculosis (MDR-TB); resistance to rifampin and isoniazid. Reflex testing is beneficial, as it allow the most rapid detection of MDR and XDR-TB patients.
If NAAT is negative for the IS6110 marker no MDDR results will be reported to the submitter.
Culture based drug susceptibility testing remains the gold standard for determining drug resistance within a MTBC isolate and will continue to be conducted in parallel with molecular methods.