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Test Code TB2LN Susceptibility, Mycobacterium tuberculosis Complex, Second Line, Varies

Infectious

Useful For

Determination of Mycobacterium tuberculosis complex minimal inhibitory concentrations to second-line antimicrobial agents

Additional Tests

Test ID Reporting Name Available Separately Always Performed
STV2 Susceptibility, Mtb Cx, 2nd Line No, (Bill Only) Yes

Testing Algorithm

When this test is ordered, the additional test will always be performed at an additional charge.

Reporting Name

Susceptibility, Mtb Complex, 2 Line

Specimen Type

Varies


Additional Testing Requirements


If organism identification is not provided, 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.



Shipping Instructions


1. For shipping information see Infectious Specimen Shipping Guidelines.

2. Place specimen in a large infectious container 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.


Specimen Stability Information

Specimen Type Temperature Time Special Container
Varies Ambient (preferred)
  Refrigerated 

Reject Due To

Agar plate Reject

Clinical Information

The Clinical and Laboratory Standards Institute (CLSI) provides a consensus protocol for the methods, antimycobacterial agents, and concentrations of each agent to be tested to permit standardized interpretation of Mycobacterium tuberculosis complex susceptibility testing results. CLSI guidelines suggest that additional agents should be tested when an isolate of M tuberculosis complex is resistant to rifampin, is monoresistant to the critical concentration of isoniazid and the physician intends to use a fluoroquinolone for therapy or is resistant to any combination of two first-line agents.

 

This test uses a broth microdilution minimal inhibitory concentration (MIC) method for susceptibility testing of M tuberculosis complex against antimycobacterial agents. Agents tested are amikacin, ethionamide, kanamycin, moxifloxacin, ofloxacin, p-aminosalicylic acid, rifabutin, and streptomycin.

Reference Values

Interpretive criteria and reporting guidelines are followed using the Clinical Laboratory Standards Institute (CLSI) M24S document.

Interpretation

Results are reported as minimal inhibitory concentrations in mcg/mL.

 

This test is used as an alternative to TB1LN / Antimicrobial Susceptibility, Mycobacterium tuberculosis Complex, First Line, Varies for ethambutol, isoniazid and rifampin when reagents are not available to perform the TB1LN test. Ethambutol, isoniazid, and rifampin are not routinely reported with this test.

Cautions

Clinical and Laboratory Standards Institute (CLSI) interpretive criteria are used for agents with established criteria. For all other agents, tentative breakpoints were established by Mayo Clinic by comparison to the critical concentration established by CLSI for each drug and are considered tentative until consensus guidelines are established.

  

Drug susceptibility testing should be performed on pure culture isolates of Mycobacterium tuberculosis complex.

Method Description

This test utilizes the Sensititre MycoTB broth microtiter dilution plate (Trek/ThermoFisher). Antimicrobials are tested according to CLSI M24 guidelines.(Thermo Scientific Sensititre MIC Susceptibility Plates for Mycobacterium tuberculosis. Product Insert. 011-MYCOTB-CID9502. Revision Date: 09/07/2016; Brown-Elliott, BA, Cirillo DM, Musser KA, Rowlinson M-C. Susceptibility Test Methods: Mycobacteria, Nocardia, and Other Actinomycetes. In: Carroll KC, Pfaller MA, eds. Manual of Clinical Microbiology, 13th Edition. ASM Press, 2023)

Day(s) Performed

Monday through Sunday

Report Available

21 to 30 days

Performing 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

87186-Susceptibility, Mtb Cx, 2nd Line

LOINC Code Information

Test ID Test Order Name Order LOINC Value
TB2LN Susceptibility, Mtb Complex, 2 Line 29579-0

 

Result ID Test Result Name Result LOINC Value
TB2LN Susceptibility, Mtb Complex, 2 Line 29579-0

Method Name

Minimum Inhibitory Concentration (MIC) by Microtiter Broth Dilution Method

Specimen Minimum Volume

See Specimen Required