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HelpMayo Test ID MTBPZ Mycobacterium tuberculosis Complex, Pyrazinamide Resistance by pncA DNA Sequencing, Varies
Infectious
Shipping Instructions
1. See Infectious Specimen Shipping Guidelines.
2. Place specimen in a large infectious container (T146) and label as an etiologic agent/infectious substance.
Necessary Information
Specimen source and suspected organism identification are required.
Specimen Required
Specimen Type: Organism
Supplies: Infectious Container, Large (T146)
Container/Tube: Middlebrook 7H10 agar slant
Specimen Volume: Isolate
Collection Instructions: Organism must be in pure culture, actively growing.
Useful For
Detection of genotypic resistance to pyrazinamide by Mycobacterium tuberculosis complex isolates
Reflex Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| MTBVP | Mtb PZA Confirmation, pnc A Sequence | No, (Bill Only) | No |
Testing Algorithm
When this test is ordered, the reflex test may be performed and charged.
Special Instructions
Method Name
DNA Sequencing
Reporting Name
Mtb PZA Resistance, pncA SequencingSpecimen Type
VariesSpecimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Varies | Ambient (preferred) | ||
| Refrigerated | |||
Reject Due To
| Agar plate | Reject |
Clinical Information
The protein product of the Mycobacterium tuberculosis complex pncA gene is an enzyme that is responsible for activation of the prodrug pyrazinamide (PZA). DNA sequencing of the Mycobacterium tuberculosis complex pncA gene can be used to detect mutations that correlate with in vitro PZA resistance.(1,2) The sequencing result can be available in as little as 1 day after the Mycobacterium tuberculosis complex isolate grows in culture, thereby providing a more rapid susceptibility result than the average 10 to 14 days required by phenotypic broth methods.
Reference Values
Pyrazinamide resistance not detected
Interpretation
Polymorphisms in the pncA gene that have been previously correlated in our laboratory with pyrazinamide (PZA) resistance will be reported as "Mutation was detected in pncA suggesting resistance to pyrazinamide."
Wildtype pncA or a silent pncA gene polymorphism (ie, no change in the amino acid translation) will be reported as "No mutation was detected in pncA."
New polymorphisms in the pncA gene that have not previously been seen in our laboratory will require additional testing using a reference broth method to determine their correlation with PZA resistance.
Cautions
According to the literature,(3) 72% to 97% of pyrazinamide (PZA)-resistant clinical isolates carry mutations in the pncA gene or promoter region. However, other resistance mechanisms (eg, changes in PZA uptake or increased PZA efflux) will not be detected by this method.
Correlation of the in vitro sequencing result with clinical presentation is strongly recommended.
Clinical Reference
1. Somoskovi A, Dormandy J, Parson LM, et al: Sequencing of the pncA Gene in members of the Mycobacterium tuberculosis complex has important diagnostic applications: identification of a species-specific pncA mutation in "Mycobacterium canettii" and the reliable and rapid predictor of pyrazinamide resistance. J Clin Microbiol. 2007;45(2):595-599
2. Dormandy J, Somoskovi A, Kreiswirth BN, Driscoll JR, Ashkin D, Salfinger M: Discrepant results between pyrazinamide susceptibility testing by the reference BACTEC 460TB method and pncA DNA sequencing in patients infected with multi-drug resistant W-Beijing Mycobacterium tuberculosis strains. Chest. 2007;131(2):497-501
3. Somoskovi A, Parson LM, Salfinger M: The molecular basis of resistance to isoniazid, rifampin, and pyrazinamide in Mycobacterium tuberculosis. Respir Res. 2001;2(3):164-168
4. Bouzouita I, Cabibbe AM, Trovato A, Draoui H, Ghariani A, Midouni B, Essalah L, Mehiri E, Cirillo DM, Slim-Saidi L. Is sequencing better than phenotypic tests for the detection of pyrazinamide resistance? Int J Tuberc Lung Dis. 2018 Jun 1;22(6):661-666. doi:10.5588/ijtld.17.0715
Method Description
Organisms identified as Mycobacterium tuberculosis complex using the Mycobacterium tuberculosis AccuProbe (GenProbe) are lysed using the PrepMan Ultra lysis buffer. Using the pncA primers described by Shenai and colleagues, an approximately 700 base pair-polymerase chain reaction (PCR) product is generated that flanks the entire pncA gene and the upstream promoter region. The PCR product is cleaned and sequenced using the Big Dye terminator v 1.1 Cycle Sequencing reagents (Applied Biosystems). Results are analyzed versus the wildtype pncA sequence using MicroSeq Microbial ID software. A custom library of non-wildtype sequences was constructed in MicroSeq. An exact match to the custom nucleotide library is required to report the result.(Shenai S, Rodrigues C, Sadani M, Sukhadia N, Mehta A: Comparison of phenotypic and genotypic methods for pyrazinamide susceptibility testing. Indian J Tuberc. 2009;56(2):82-90)
Day(s) Performed
Varies
Report Available
7 to 21 daysSpecimen Retention Time
1 yearPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
87153-Mtb PZA Confirmation, pncA Sequence
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| MTBPZ | Mtb PZA Resistance, pncA Sequencing | 46245-7 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| MTBPZ | Mtb PZA Resistance, pncA Sequencing | 46245-7 |