MDDR in M. tuberculosis complex

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Brief Description

Molecular Detection of Drug Resistance (MDDR) is Polymerase Chain Reaction (PCR) testing provided by the Centers for Disease Control and Prevention (CDC) aimed at the detection of genetic markers of drug resistance for Mycobacterium tuberculosis complex (MTBC). Results are available in days as compared to weeks for conventional drug susceptibility testing.

Laboratory Unit



Deoxyribonucleic Acid (DNA) analysis for drug resistant mutations.

Specimen Requirements for Submission

Request for MDDR testing can be made if one of the following criteria is met:
  • High-risk of Rifampin resistance of Multi-Drug Resistant Tuberculosis (MDR-TB) (including previously treated Tuberculosis (TB) case, drug resistant TB contact, foreign-born from area with high rates of MDR-TB).
  • Known Rifampin resistant isolates.
  • High profile patients (e.g. daycare workers, healthcare provider).
  • Adverse reactions (e.g. patients allergic to Rifampin).
  • Mixed or non-viable cultures.
If your patient meets the above guidelines, contact the MSPHL, TB Unit at 573-751-3334.  You will be given instructions for MDDR testing.


Submit reference isolates of TB using a Category A mailer provided by the MSPHL in accordance with the Infectious Substance, Category A shipping guidelines.

Acceptable Specimen

Only isolates of M. tuberculosis complex can be submitted for MDDR testing.

Test Request Form(s)

Tuberculosis Test Request Form

Possible Results

Refer to the CDC Result Report

Reference Range


Unacceptable Conditions

Leaked during transport
No name on specimen
Mixed culture
Nonviable organism

Interfering Substances


Result Reported

Most results are reported within 24 – 48 hours after CDC receives the specimen.



CPT Codes




Additional Information

Limitations of MDDR:  Potential to identify mutations that do not confer phenotypic resistance.  Not all genetic loci associated with resistance are known, therefore, a susceptible molecular result does not rule out resistance.