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microbial diseases laboratory

Test Order Mycobacterium tuberculosis complex:
Molecular Detection of Drug Resistance by Pyrosequencing Assay

Pre-Approval Required

Yes

Supplemental Information or Form

Form LAB 444, 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. Smear negative samples need approval for submission

Minimum Volume Required

0.5 ml for sediment or broth, more if preferred

Storage & Preservation of Sample/Specimen Prior to Shipping

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

Transport

None

Sample/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 line panel for detecting isoniazid resistance are katG, inhA and ahpC promoters and fabG1; that for rifampin is rpoB. The molecular targets in the second line panel for detecting resistance to quinolones is gyrA and that for kanamycin, amikacin capreomycin and kanamycin is rrs.

  • The second line panel is tested when any mutation is detected in the first panel, or requested.

  • For more information on pyrosequencing, please contact us.

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, Mycotic and Parasitic Diseases Section
TB DST Unit (510) 412-3929 or (510) 412-3949

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