Test Methodology
|
Phenotypic drug susceptibility testing of Mycobacterium tuberculosis complex at critical concentrations by BACTEC MGIT 960 system. Routinely tested drugs: isoniazid (INH) 0.1 μg/ml, rifampin (RIF) 1 µg/ml, pyrazinamide (PZA) 100 µg/ml, and ethambutol (EMB) 5 µg/ml. Submitters may request the alternative first-line DST panel where moxifloxacin (MFX) 0.25 µg/ml is tested instead of EMB.
|
Reflex Testing
Criteria
|
If resistance to any of the first-line drugs (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 μg/ml is detected, susceptibility testing to INH at 0.4 μg/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.
|
Pre-Approval Required
|
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)
|
Barcode submittal form 444 “Mycobacteriology-Drug Susceptibility Testing of MTBC (CA only)” or instructions for using the MDL Lab Web Portal (ETOR) can be found at: MDL Submission Instructions and Forms.
Indicate submitter’s test results on the submittal form.
|
Required Specimen Type(s)
|
Pure culture on solid or liquid media.
Slants (LJ/ 7H10) or liquid cultures (MGIT broth) are the preferred culture media for submission.
|
Minimum Volume Required
|
Viable growth should be present on subculture.
1.0 mL minimum if broth submitted
|
Specimen Stability
|
Room Temp: up to 4 weeks.
Refrigerated (2 – 8°C): up to 6 months.
Frozen: Subculture prior to submission.
If culture age exceeds above mentioned, subculture prior to submission and submit fresh culture
|
Rejection Criteria
|
- Samples with insufficient or conflicting labelling
- Leaking samples
- Isolates with no growth
- Isolates that are nonviable
- Mixed cultures
- Specimen/sample types not meeting acceptance criteria
|
Storage/Transport Conditions
|
Grow isolate under appropriate conditions and verify purity prior to shipping. Isolates may be stored refrigerated or at ambient temperature prior to shipping.
|
Transport Medium,
if applicable
|
Not Applicable
|
Specimen Labeling
|
Two identifiers, including patient full name, and at least one other identifier (specimen accession number, date of birth, medical record number).
|
Shipping Instructions and Specimen Handling Requirements
|
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 Health
Microbial Diseases Laboratory
ATTN: TB Drug Susceptibility Testing Unit
850 Marina Bay Parkway, Specimen Receiving Room B106
Richmond, CA 94804
|
Specimen Collection Instructions, if applicable
|
Not Applicable
|
Turnaround Time
|
17 days
|
Interferences & Limitations
|
Results may be delayed or unattainable if mixed culture is submitted.
|
Reference Range
|
Not Applicable
|
Additional Information
|
Isolates that are tested at MDL will be forwarded to the CDC if further characterization is needed or requested.
|
MDL Point of Contact
|
For questions regarding submissions, please email
CDPHTBDST@cdph.ca.gov or call the MMPDS Section at (510) 412-3929
|