ARUP's Laboratory Test Directory

0060217: Antimicrobial Susceptibility - AFB/Mycobacteria

Test Mnemonic: MA AFB
Methodology: Varies with organism identification

Performed: Mon-Fri

Reported: Varies

Specimen Required:  
Collect: Viable organism in pure culture on solid or in liquid media.

Transport: Sealed container at 20-25°C.

Submit specimen according to Infectious Substance, Category A, shipping guidelines.

Pediatric Collection/Transport:

Submit specimen according to Infectious Substance, Category A, shipping guidelines.

Unacceptable Conditions: Mixed cultures, nonviable organisms, or organisms submitted on an agar plate.

Stability: Ambient: 2 weeks; Refrigerated: 2 weeks; Frozen: 2 weeks

Reference Interval:
By report

I.  M. tuberculosis, Primary Panel
Methodology: MGIT™ 960
The interpretation provided is based on results for the following drugs at the stated concentrations:
Drugs tested: Ethambutol: 5.0 µg/mL, Isoniazid: 0.1 µg/mL, (0.4 µg/mL if resistant to 0.1 µg/mL), Pyrazinamide: 100 µg/mL, Rifampin: 1.0 µg/mL.

This procedure screens isolates of M. tuberculosis complex for drug resistance. The procedure does not use serial dilutions to provide quantitative MIC values. Single critical concentrations for each antimycobacterial agent used have been defined by the United States Public Health Service.

CPT Code(s): 87188 x4

II. M. tuberculosis, Secondary Panel
Methodology: Agar proportion
Note: If M. tuberculosis isolate is resistant to rifampin or any two primary drugs, a secondary panel is indicated.  This panel will be performed by request as a sendout test. The interpretation provided is based on testing for the following drugs at the stated concentrations:
Drugs tested: Amikacin: 6 µg/mL; capreomycin: 10 µg/mL; cycloserine: 60 µg/mL; ethionamide: 10 µg/mL;  kanamycin: 6 µg/mL; PAS: 8 µg/mL; ofloxacin: 2 µg/mL; streptomycin at a low level (2.0 µg/mL) and a high level (4.0 µg/mL).

CPT Code(s):  87190 x6, 87188

III.  M. avium-intracellulare complex (MAC)
Methodology: Broth Microdilution
Drugs tested: Amikacin, ciprofloxacin, clarithromycin, ethambutol, gatifloxacin, linezolid, moxifloxacin, rifabutin, rifampin and streptomycin.

Clarithromycin is the only drug for which CLSI provides interpretive guidelines.  Clarithromycin results predict azithromycin.  For drugs other than clarithromycin or azithromycin, there are no CLSI interpretive guidelines. Therefore, only MIC is reported.  Because MIC results do not predict clinical response, rifampin, rifabutin, and ethambutol MICs are not reported.

CPT Code(s): 87186

IV.  Rapid Growing Mycobacteria
Methodology: Broth Microdilution
Drugs tested: Amikacin, cefoxitin, ciprofloxacin, clarithromycin, gatifloxacin, imipenem (M. fortuitum complex only), linezolid, minocycline, tobramycin (M. chelonae only), and trimethoprim/sulfamethoxazole (TMP/SXT).

CPT Code(s): 87186

V.  Other Slowly-Growing Nontuberculosus Mycobacteria (NTM)
Methodology: Broth Microdilution  

CLSI recommends that isolates of M. kansasii be tested against rifampin only. Rifampin-susceptible isolates are also susceptible to rifabutin.  If the isolate is rifampin-resistant, the following secondary drugs will also be reported: Amikacin, ciprofloxacin, clarithromycin, ethambutol, gatifloxacin, moxifloxacin, rifabutin, streptomycin and trimethoprim-sulfamethoxazole. Currently there are no CLSI interpretive criteria for gatifloxacin and moxifloxacin; therefore, only the MIC is reported.

M. marinum isolates are tested against amikacin, clarithromycin, ethambutol, minocycline, rifampin, and trimethoprim-sulfamethoxazole. Interpretation is based upon CLSI guidelines.

Slowly-growing NTM other than M.kansasii and M. marinum are tested against amikacin, ciprofloxacin, clarithromycin, ethambutol, gatifloxacin, moxifloxacin, rifabutin, rifampin, and streptomycin.
Interpretive criteria for all but gatifloxacin and moxifloxacin  are based on proposed CLSI guidelines.  Currently there are no CLSI interpretive criteria for gatifloxacin and moxifloxacin; therefore, only the MIC is reported.

CPT Code(s): 87186

Interpretive Data:


Please refer to Statement B in the Compliance Statements section in the front of the Laboratory Test Directory.



Note:
AFB susceptibility testing is billed at the panel level (I-V).  Charges will vary based on organism identified.  An additional handling fee will be billed for all organisms submitted that are not in pure culture as indicated in the specimen requirements.