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microbial diseases laboratory branch

Test Name

Mycobacterium tuberculosis Complex: Drug Susceptibility Testing, First-Line



Test Methodologyā€‹

ā€‹Phenotypic drug susceptibility testing of Mycobacterium tuberculosis complex at critical concentrations by BACTEC MGIT 960 system.ā€‹ā€‹ Routinely tested drugs: isoniazid (INH) 0.1 Ī¼g/ml, rifampin (RIF) 1 Āµg/ml, pyrazinamide (PZA) 100 Āµg/ml, and ethambutol (EMB) 5 Āµg/ml. Submitters may request the alternative first-line DST panel where moxifloxacin (MFX) 0.25 Āµg/ml is tested instead of EMB. ā€‹ā€‹

ā€‹Reflex Testing
Criteria

ā€‹ā€‹ā€‹ā€‹If resistance to any of the first-line drugs (ā€‹except PZA) is detected, second-line drug susceptibility testing will be performed.

The default second-line drug panel includes amikacin (AMK), capreomycin (CAP), kanamycin (KAN), rifabutin (RFB), ethionamide (ETA), and MFX. If MFX testing was previously performed as part of alternative first-line DST and resistance to RIF, INH, or MFX was observed, EMB will be included in the second-line DST panel.

In addition, if resistance to INH at 0.1 Ī¼g/ml is detected, susceptibility testing to INH at 0.4 Ī¼g/ml will be performed.

Molecular detection of drug resistance by pyrosequencing may also be performed on cultures including mixed or contaminated cultures when there is known or suspected phenotypic drug resistance.

ā€‹Pre-Approval Requiredā€‹
ā€‹ā€‹No, unless:
Duplicate submission, i.e., samples from the same patient collected within 3 months from prior collection date.

Supplemental Information and Required Form(s)ā€‹
Barcode submittal form 444 ā€œMycobacteriology-Drug Susceptibility Testing of MTBC (CA only)ā€  or instructions for using the MDL Lab Web Portal (ETOR) can be found at:  MDL Submission Instructions and Formsā€‹.ā€‹ā€‹
ā€‹Indicate submitterā€™s test results on the submittal form.ā€‹ā€‹ā€‹
ā€‹Required Specimen Type(s)

ā€‹Pure culture ā€‹on solid or liquid media.
Slants (LJ/ 7H10) or liquid cultures (MGIT broth) are the preferred culture media for submission.

ā€‹Minimum Volume Required
ā€‹Viable growth should be present on subculture.
ā€‹ā€‹1.0 mL minimum if broth submitted

ā€‹Specimen Stabilityā€‹

ā€‹ā€‹ā€‹Room Temp: up to 4 weeks.
Refrigerated (2 ā€“ 8Ā°C): up to 6 months.
Frozen: Subculture prior to submission.
If culture age exceeds above mentioned, subculture prior to submission and submit fresh culture
ā€‹Rejection Criteria

  • ā€‹ā€‹Samples with insufficient or conflicting labellingā€‹ā€‹
  • ā€‹Leaking samples
  • ā€‹Isolates with no growth
  • ā€‹Isolates that are nonviable
  • Mixed cultures
  • Specimen/sample types not meeting acceptance criteriaā€‹ā€‹
ā€‹Storage/Transport Conditions

ā€‹Grow isolate under appropriate conditions and verify purity prior to shipping. Isolates may be stored refrigerated or at ambient temperature prior to shipping.ā€‹

ā€‹Transport Medium,ā€‹
if applicableā€‹ā€‹

ā€‹Not Applicable
ā€‹Specimen Labeling

ā€‹Two identifiers, including patient full name, and at least one other identifier (specimen accession number, date of birth, medical record number).ā€‹ā€‹
ā€‹Shipping Instructions and Specimen Handling Requirements

ā€‹ā€‹ā€‹Ship isolates at ambient temperature or with cold packs; do not freeze.

Follow the appropriate DOT/IATA approved shipping procedures. Suspected or confirmed MTBC cultures should be shipped as a Category A Infectious Substance, Affecting Humans (UN2814).

Ensure that culture isolates are sent in media flask or tubes containing a screw-top cap that is additionally sealed with parafilm or tape for additional protection against leaking. DO NOT send plate cultures.

Ship to:

California Department of Public Healthā€‹
Microbial Diseases Laboratory ā€‹
ATTN:  TB Drug Susceptibility Testing Unit ā€‹ā€‹
850 Marina Bay Parkway, Specimen Receiving Room B106
Richmond, CA  94804

ā€‹Specimen Collection Instructions, if applicable

ā€‹ā€‹Not Applicable
ā€‹Turnaround Time


ā€‹17 daysā€‹
ā€‹Interferences & Limitations

ā€‹ā€‹Results may be delayed or unattainable if mixed culture is submitted.

ā€‹Reference Range
ā€‹Not Applicableā€‹
ā€‹Additional Information
ā€‹ā€‹Isolates that are tested at MDL will be forwarded to the CDC if further characterization is needed or requested. 

ā€‹MDL Point of Contact
ā€‹For questions regarding submissions, please email  CDPHTBDST@cdph.ca.gov or call the MMPDS Section at (510) 412-3929ā€‹ā€‹

ā€‹

MDL ā€‹ā€‹Procedure Changeā€‹ Notification: Pyrazinamide (PZA) Drug Susceptibility Testing for TBā€‹ā€‹
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