Mycobacterium avium Complex Susceptibility−Broth Dilution
- M avium Complex Susceptibility Testing
- AFB Susceptibility Testing
- MAC Susceptibility Testing
- Susceptibility Testing, M avium Complex
- Susceptibility Testing, MAC
Determine the susceptibility of Mycobacterium avium complex isolates to a profile of antimycobacterial agents. Routine susceptibility testing of MAC isolates is recommended for clarithromycin only since no correlation between in vitro susceptibility results for MAC and clinical response for agents other than macrolides has been established.1 Initial isolates from patients with previously untreated MAC lung disease should be tested against clarithromycin to establish a baseline value. Other MAC isolates to be tested should include:
Failure to take all drugs in a multidrug regimen can lead to a shift toward resistant organisms and treatment failure. Nontuberculous mycobacteria, particularly strains of the M avium complex, are resistant to those drugs used for therapy of M tuberculosis. Clarithromycin (and azithromycin) are the only agents for which CLSI interpretive guidelines are established. Treatment of MAC for most patients with nodular/bronchiectatic disease includes a three-times-weekly regiment of clarithromycin or azithromycin, rifampin, and ethambutol. For patients with MAC lung disease or severe nodular/bronchiectatic disease, a daily regime of clarithromycin or azithromycin, rifampin or rifabutin, and ethambutol with consideration of three-times-weekly amikacin or streptomycin early in therapy is recommended. Treatment should occur until the patient is culture negative for one year. Treatment of disseminated MAC disease should include clarithromycin or azithromycin and ethambutol with or without rifabutin until the symptoms have resolved and cell-mediated immune function has returned.
Mycobacterium avium complex isolated from a primary clinical specimen, on a submitted AFB conventional solid medium, or an AFB broth medium.
Pure culture isolate on an AFB conventional solid medium or a minimum of 1 mL of AFB broth medium.
Conventional or broth medium, tightly sealed, in etiologic agent packaging.
Maintain media at room temperature.
Specimen received in leaking or in broken transport tube or vial; specimen received in expired transport medium; mixed culture; unlabeled culture or name discrepancy between specimen and request label.
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