Mayo Test Catalog, (Sorted By Test Name) - Mayo Medical ...

MTBRP
88807
MTBPZ
56099
Mycobacterium tuberculosis Complex, Molecular Detection,
PCR
Clinical Information: Each year, Mycobacterium tuberculosis accounts for nearly 2 million deaths
and is responsible for 9 million newly diagnosed cases of tuberculosis worldwide. Mycobacterium
tuberculosis is spread from person-to-person via respiratory transmission, and has the potential to become
resistant to many or all of the antibiotics currently used if antimycobacterial treatment is not promptly
initiated. Therefore, rapid and accurate detection of Mycobacterium tuberculosis in patient specimens is of
clinical and public health importance. Conventional culture methods can generally detect Mycobacterium
tuberculosis in 2 to 3 weeks, although up to 8 weeks of incubation may be required in some instances.
Developed at Mayo Clinic, this rapid PCR assay detects Mycobacterium tuberculosis complex DNA
directly from respiratory specimens and other specimens without waiting for growth in culture and,
therefore, the results are available the same day the specimen is received in the laboratory. The assay
targets a unique sequence within the katG gene, which is present in members of the Mycobacterium
tuberculosis complex. In addition, the assay can detect genotypic resistance to isoniazid mediated by
mutations in the katG target, when present.
Useful For: Rapid detection of Mycobacterium tuberculosis complex, preferred method Diagnosis of
tuberculosis, when used in conjunction with mycobacterial culture
Interpretation: A positive result indicates the presence of Mycobacterium tuberculosis complex DNA.
Members of the Mycobacterium tuberculosis complex detected by this assay include Mycobacterium
tuberculosis, Mycobacterium bovis, Mycobacterium bovis Bacillus Calmette-Guerin, Mycobacterium
africanum, Mycobacterium canetti, and Mycobacterium microti. The other species within the
Mycobacterium tuberculosis complex (Mycobacterium bovis subspecies caprae and Mycobacterium
pinnepedi) should, in theory, be detected using the primer and probe sequences in this assay, but they
have not been tested at this time. This assay method does not distinguish between the species of the
Mycobacterium tuberculosis complex. A negative result indicates the absence of detectable
Mycobacterium tuberculosis complex DNA. Isoniazid (INH) resistance mediated through a katG mutation
will be reported when observed but lack of a katG mutation does not imply that the isolate is susceptible
to INH. There are other genetic loci in addition to katG that can contribute to resistance for this drug.
Reference Values:
Not applicable
Clinical References: 1. Iseman MD: A clinicianâ€s guide to tuberculosis. Philadelphia, PA.
Lippincott Williams & Wilkins, 2000 2. Centers for Disease Control and Prevention: Treatment of
Tuberculosis, American Thoracic Society, CDC, and Infectious Diseases Society of America. MMWR
Morb Mortal Weekly Rep 2003;52(No. RR-11):1-88
Mycobacterium tuberculosis Complex, Pyrazinamide
Resistance by pncA DNA Sequencing
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.
Useful For: Detection of genotypic resistance to pyrazinamide by Mycobacterium tuberculosis
complex isolates
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." Wild-type 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
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