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 Test Order

Mycobacterium tuberculosis complex:
Molecular Detection of Drug Resistance

Pre-Approval Required

Yes

Supplemental Information or Form

Form LAB 444 (03/12) (MDL-N-25), EXAMINATION FOR MYCOBACTERIA TUBERCULOSIS DRUG SUSCEPTIBILITY

Performed on Specimens from

Patients suspected of having drug-resistant tuberculosis, patients who are especially susceptible to treatment failure, cultures of M. tb complex mixed with non-TB mycobacteria or other bacteria.

Acceptable Sample/ Specimen Type for Testing

Sediment or culture.   At least 0.5 ml of a concentrated sample which is acid-fast smear positive.

Minimum Volume Required

0.5 ml for sediment, more if preferred.

Storage & Preservation of Specimen Prior to Shipping

If sediment, refrigerate. If culture, incubate at 35-37°C.

Transport Medium

None

Specimen Labeling

Patient’s name, accession number

Shipping Instructions which Include Specimen Handling Requirements

Ship cultures of M. tb complex as infectious substances.   Sediments may be shipped as diagnostic specimens with a cold pack.

Test Methodology

  • The method used to identify mutations associated with drug resistance is pyrosequencing (PSQ). The molecular targets in the first panel for detecting isoniazid resistance are katG, inhA and ahpC promoters and fabG1; that for rifampin is rpoB. The molecular targets in the second panel for detecting resistance to quinolones is gyrA and that for kanamycin, amikacin capreomycin and kanamycin is rrs.
  • The second panel is tested when any mutation is detected in the first panel, or requested.
  • For more information on pyrosequencing, see the bulletin “Pyrosequencing (PSQ) for XDR TB Screening” (see Submission Instruction and Forms page).

Turnaround Time

1 to 3 days

Interferences & Limitations

Inhibitory substances in the specimen may prevent successful DNA amplification and pyrosequencing.

Additional Information

None

MDL Points of Contact

Mycobacterial Diseases Section (drug susceptibilities) (510) 412-3929
Email: grace.lin@cdph.ca.gov

 

 
 
Last modified on: 8/26/2016 11:13 AM