Susceptibility testing of Mycobacterium tuberculosis complex isolates growing in pure culture against pyrazinamide
Confirming M tuberculosis complex resistance to pyrazinamide
Test Id | Reporting Name | Available Separately | Always Performed |
---|---|---|---|
MTBVP | Mtb PZA Confirmation, pnc A Sequence | No, (Bill Only) | No |
Test Id | Reporting Name | Available Separately | Always Performed |
---|---|---|---|
STVP | Susceptibility, Mtb Complex, PZA | No, (Bill Only) | Yes |
When this test is ordered the additional test will always be performed at an additional charge.
If resistance to pyrazinamide is detected, the reflex test for confirmation of resistance will be performed at an additional charge.
Broth Dilution at Critical Drug Concentrations
Acid-Fast Bacilli (AFB)
AFB (Acid-Fast Bacilli)
Antibiotic Susceptibility
Antimicrobial Susceptibility, Mycobacterium tuberculosis
Bacillus, Acid-Fast
MTB (Mycobacterium tuberculosis)
Mycobacteria Antimicrobial Susceptibility (MIC) (Minimum Inhibitory Concentration)
Mycobacterium tuberculosis (MTB)
Susceptibility Testing
Susceptibility, Mycobacterium tuberculosis
TB (Tuberculosis)
Tubercle Bacilli: Mycobacterium tuberculosis
Tuberculosis (TB)
When this test is ordered the additional test will always be performed at an additional charge.
If resistance to pyrazinamide is detected, the reflex test for confirmation of resistance will be performed at an additional charge.
Varies
To test for first-line agents, isoniazid, rifampin and ethambutol, order TB1LN / Antimicrobial Susceptibility, Mycobacterium tuberculosis Complex, First Line, Varies
CTB / Mycobacteria and Nocardia Culture, Varies or CTBID / Culture Referred for Identification, Mycobacterium and Nocardia, Varies must also be ordered and will be charged separately unless identification of organism is provided.
1. See Infectious Specimen Shipping Guidelines in Special Instructions.
2. Place specimen in a large infectious container (T146) and label as an etiologic agent/infectious substance.
Specimen source and suspected organism identification are required.
Question ID | Description | Answers |
---|---|---|
Q00M0074 | Specimen source (Required) and Organism Identification (Required unless concurrent identification test is ordered) |
Specimen Type: Organism
Supplies: Infectious Container, Large (T146)
Container/Tube: Middlebrook 7H10 agar slant
Specimen Volume: Isolate
Collection Instructions:
If not ordering electronically, complete, print, and send a Microbiology Test Request (T244) with the specimen.
Other | Agar plate |
Specimen Type | Temperature | Time | Special Container |
---|---|---|---|
Varies | Ambient (preferred) | ||
Refrigerated |
Susceptibility testing of Mycobacterium tuberculosis complex isolates growing in pure culture against pyrazinamide
Confirming M tuberculosis complex resistance to pyrazinamide
When this test is ordered the additional test will always be performed at an additional charge.
If resistance to pyrazinamide is detected, the reflex test for confirmation of resistance will be performed at an additional charge.
Primary treatment regimens for Mycobacterium tuberculosis complex often include isoniazid, rifampin, ethambutol, and pyrazinamide (PZA). Susceptibility testing of each M tuberculosis complex isolate against these first-line antimycobacterial agents is a key component of patient management.
The Clinical and Laboratory Standards Institute (CLSI) provides consensus protocols for the methods, antimycobacterial agents, and critical concentrations of each agent to be tested in order to permit standardized interpretation of M tuberculosis complex susceptibility test results. Current recommendations indicate that laboratories should use a rapid broth method in order to obtain M tuberculosis complex susceptibility data as quickly as possible to help guide patient management. According to the CLSI, resistance can be confirmed by another method or by another laboratory at the discretion of the testing laboratory.
This test uses an FDA-cleared commercial system for rapid broth susceptibility testing of M tuberculosis complex against PZA. Since the literature indicates that broth testing of PZA can, at times, produce falsely resistant results, resistance to PZA by the broth method is automatically confirmed by pncA DNA sequencing. The pncA gene of M tuberculosis complex is responsible for activation of the prodrug PZA and hence PZA activity. Variations in the pncA gene and upstream promoter region have been reported to account for the majority (70%-97%) of PZA-resistant isolates. However, 3% to 30% of PZA-resistant isolates do not have a corresponding pncA variant and other genes (eg, rpsA) may also play a role.
A separate test is available for testing of the other first-line agents (isoniazid, rifampin and ethambutol). If desired, this must be ordered separately; TB1LN / Antimicrobial Susceptibility, Mycobacterium tuberculosis Complex, First Line, Varies.
Results are reported as susceptible or resistant.
Mycobacterium tuberculosis complex isolates are reported as susceptible or resistant to pyrazinamide at the critical concentration.
For resistant organisms, confirmatory testing using pncA DNA sequencing is automatically performed and the presence or absence of pncA variations associated with pyrazinamide resistance is reported.
In vitro susceptibility does not guarantee clinical response. Therefore, the decision to treat with a particular agent should not be based solely on the antimicrobial susceptibility testing result.
Susceptibility testing should be performed on pure culture isolates of Mycobacterium tuberculosis complex.
Some variants associated with pyrazinamide resistance that may occur outside of the pncA promoter and gene region and may therefore not be confirmed by DNA sequencing of this target.
1. Blumberg HM, Burman WJ, Chaisson RE, et al: American Thoracic Society/Centers for Disease Control and Prevention/Infectious Diseases Society of America: treatment of tuberculosis. Am J Respir Crit Care Med 2003;167(4):603-662
2. Woods GL, Lin S-Y G, Desmond EP: Susceptibility test methods: Mycobacteria, Nocardia and other Actinomycetes. In Manual of Clinical Microbiology.10th edition. Edited by J Versalovic, KC Carroll, G Funke, et al. ASM Press, 2011, pp 1215-1238
3. Dormandy J, Somoskovi A, Kreiswirth BN, et al: Discrepant results between pyrazinamide susceptibility testing by the reference BACTEC 460TB method and pncA DNA sequencing in patients infected with multidrug-resistant W-Beijing Mycobacterium tuberculosis strains. Chest 2007;131:497-501
4. Chedore P, Bertucci L, Wolfe J: Potential for Erroneous Results Indicating Resistance When Using the BACTEC MGIT 960 System for Testing Susceptibility of Mycobacterium tuberculosis to Pyrazinamide. J Clin Microbiol 2010 Jan;48(1):300-301
5. Campbell PJ, Morlock GP, Sikes RD, et al: Molecular resistance of mutations associated with first- and second-line drug resistance compared with conventional drug susceptibility testing of Mycobacterium tuberculosis. Antimicrob Agents Chemother 2011;55:2032-2041
6. Shi W, Zhang X, Jiang X, et al: Pyrazinamide inhibits trans-translation in Mycobacterium tuberculosis. Science 2011;333:1630-1632
7. CLSI, Susceptibility Testing of Mycobacteria, Nocardiae, and Other Actinomycetes; Approved Standard, Third edition. CLSI document M24. Clinical and Laboratory Standards Institute, 2018
8. CLSI. Performance Standards for Susceptibility Testing of Mycobacteria, Nocardia species, and Other Aerobic Actinomycetes. First edition. CLSI supplement M62. Clinical and Laboratory Standards Institute; 2018
9. LaBombardi VJ: Comparison of the ESP and BACTEC Systems for testing susceptibilities of Mycobacterium tuberculosis complex isolates to pyrazinamide. J Clin Microbiol 2002;40:2238-2239
10. Espasa M, Salvado M, Vicente E, et al: Evaluation of the VersaTREK system compared to the Bactec MGIT 960 system for first-line drug susceptibility testing of Mycobacterium tuberculosis. J Clin Microbiol 2012;50:488-491
11. 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. Confirmation of pyrazinamide resistance is done using Sanger dideoxy sequencing of approximately 700bp of the pncA gene and promoter region. J Clin Microbiol 2007;45:595-599
12. Jureen P, Werngren J, Toro JC, Hoffner S: Pyrazinamide resistance and pncA gene mutations in Mycobacterium tuberculosis. Antimicrob Agents Chemother 2008;52:1852-1854
This test method is based on presence or absence of growth of Mycobacterium tuberculosis in broth cultures with the presence of critical concentrations of the antimycobacterial drug pyrazinamide. One of 2 FDA-cleared platforms (VersaTREK or BD MGIT 960) may be used.
The VersaTrek platform uses the presence or absence of a pressure increase inside broth vials containing M tuberculosis in the presence of critical concentrations of the antimycobacterial drug pyrazinamide. Increasing pressure indicates the presence of actively growing M tuberculosis that is resistant pyrazinamide at 300 mcg/mL. Low or undetectable pressure increases in the presence of critical drug concentration suggests a lack of M tuberculosis growth and susceptibility to pyrazinamide 300 mcg/mL.(Package insert: VersaTREK Mycobacteria Detection and Susceptibility Testing system, TREK Diagnostics, 04/ 2014)
The BACTEC MGIT 960 platform uses the production and measurement of fluorescence within a Mycobacterial Growth Indicator Tube (MGIT) in the presence of actively growing M tuberculosis complex isolates in the presence of critical concentration of the antimycobacterial drug pyrazinamide. Low or undetectable levels of fluorescence in the presence of critical drug concentrations suggests lack of M tuberculosis growth and susceptibility to pyrazinamide at 100 mcg/mL. Increased fluorescence suggests active growth of M tuberculosis and resistance to pyrazinamide at 100 mcg/mL.(Package insert: BACTEC MGIT 960 SIRE Kit, BD Diagnostics, 10/ 2016)
Monday through Sunday
This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.
87188-Susceptibility, Mycobacterium tuberculosis Complex, Pyrazinamide
87153-Mtb PZA Confirmation, pncA Sequencing (if appropriate)
Test Id | Test Order Name | Order LOINC Value |
---|---|---|
TBPZA | Susceptibility, Mtb Complex, PZA | 56026-8 |
Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
---|---|---|
TBPZA | Susceptibility, Mtb Complex, PZA | 56026-8 |
Change Type | Effective Date |
---|---|
Test Status - Test Down | 2023-03-13 |
Test Status - Test Delay | 2023-02-13 |
Test Status - Test Resumed | 2022-11-30 |
Test Status - Test Down | 2022-01-20 |
Test Status - Test Resumed | 2021-08-16 |
Test Status - Test Down | 2021-07-14 |
Test Status - Test Delay | 2021-06-01 |