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Test Code MMLSG Antimicrobial Susceptibility, Acid-Fast Bacilli, Slowly Growing, Varies

Infectious

Additional Codes

Internal / Beaker: LAB4147

External: SLOAFBSUSC

Reporting Name

Susc, AFB, Slowly Growing

Useful For

Determination of resistance of slowly growing mycobacteria to antimicrobial agents

Additional Tests

Test ID Reporting Name Available Separately Always Performed
RSLG Susceptibility Slow Grower No, (Bill Only) Yes

Testing Algorithm

When this test is ordered, susceptibility for slow growers will be performed at an additional charge. Antimicrobials are tested and reported using the Clinical and Laboratory Standards Institute (CLSI) guidelines.(1,2)

 

Antimicrobials tested for Mycobacterium avium complex (MAC): amikacin, clarithromycin, clofazimine, linezolid, and moxifloxacin. Per the CLSI standards set in document M24 for susceptibility testing of M avium complex, Minimum inhibitory concentration (MIC) data for ethambutol, rifampin, and rifabutin have shown poor correlation with clinical response.(1,2) Therefore, although these drugs are in the recommended Infectious Diseases Society of America treatment regimen for MAC, breakpoints for these agents that separate susceptible from resistant strains cannot be determined.(3,4) Reporting of MICs for these drugs is not recommended for use in patient care. Synergy testing for nontuberculous mycobacteria has also not been standardized and its value is unclear at this time. For these reasons, ethambutol, rifampin, rifabutin and combinations of these drugs will not be tested or reported. M avium complex isolates will not be forwarded to other institutions for susceptibility testing of rifampin, rifabutin, ethambutol or synergy testing since this practice is not recommended by the CLSI nor the IDSA.(5,6) An Infectious Diseases expert with experience in difficult or refractory MAC cases should be consulted since in vitro MIC values are not useful for these drugs.

 

Antimicrobials tested for all other slowly growing Mycobacterium species: amikacin, clarithromycin, clofazimine, ciprofloxacin, doxycycline, linezolid, minocycline, moxifloxacin, rifabutin, rifampin, and trimethoprim /sulfamethoxazole. Interpretive criteria are provided according to the CLSI standards.(1,2)

 

Clofazimine interpretive criterion is not available.

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Varies


Ordering Guidance


For Mycobacterium tuberculosis complex, see TB1LN / Antimicrobial Susceptibility, Mycobacterium tuberculosis Complex, First Line, Varies and TBPZA / Susceptibility, Mycobacterium tuberculosis Complex, Pyrazinamide, 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


1. Specimen source is required.

2. Organism identification is required unless either CTB / Mycobacteria and Nocardia Culture, Varies or CTBID / Culture Referred for Identification, Mycobacterium and Nocardia, Varies is also ordered.



Specimen Required


Specimen Type: Organism

Supplies: Infectious Container, Large (T146)

Container/Tube: Middlebrook 7H10 agar slant or other appropriate media

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 

Reference Values

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

Day(s) Performed

Varies

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

LOINC Code Information

Test ID Test Order Name Order LOINC Value
MMLSG Susc, AFB, Slowly Growing 29579-0

 

Result ID Test Result Name Result LOINC Value
MMLSG Susc, AFB, Slowly Growing 29579-0

Report Available

12 to 35 days

Reject Due To

Agar plate Reject

Method Name

Microtiter Broth Dilution

Forms

If not ordering electronically, complete, print, and send a Microbiology Test Request (T244) with the specimen.

Specimen Minimum Volume

See Specimen Required

Secondary ID

34805