MMLRG - Clinical: Antimicrobial Susceptibility, Acid-Fast Bacilli, Rapidly Growing

Test Catalog

Test Name

Test ID: MMLRG    
Antimicrobial Susceptibility, Acid-Fast Bacilli, Rapidly Growing

Useful For Suggests clinical disorders or settings where the test may be helpful

Determination of resistance of rapidly growing mycobacteria to antimicrobial agents

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

When this test is ordered, Susceptibility Rapid Grower will be performed and charged.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

The rapidly growing species of mycobacteria (eg, Mycobacterium fortuitum, Mycobacterium peregrinum, Mycobacterium chelonae, Mycobacterium abscessus, and Mycobacterium mucogenicum) are seen with increasing frequency as causes of infection. Some examples of infections caused by this group of mycobacteria are empyema, subcutaneous abscess, cutaneous ulcerative and nodular lesions, peritonitis, endometriosis, bacteremia, keratitis, and urinary tract, prosthetic joint, wound, and disseminated infections.


Rapidly growing mycobacteria differ from other species of mycobacteria by their growth rates, metabolic properties, and antimicrobial susceptibility profiles. Most species are susceptible to some of the traditional antimycobacterial agents, but rapidly growing species may exhibit resistance to certain antimycobacterial agents. In contrast, they often are susceptible to several of the antibacterial agents used to treat common bacterial infections. Therefore, the antimicrobial susceptibility profile of an organism within this group varies depending on the species.


Antimicrobials tested in this assay are amikacin, cefoxitin, ciprofloxacin, clarithromycin, doxycycline, imipenem, tobramycin, trimethoprim/sulfamethoxazole, linezolid, moxifloxacin, minocycline and tigecycline.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.


Susceptible (mcg/mL)

Intermediate (mcg/mL)

Resistant (mcg/mL)


< or =16


> or =64


< or =16


> or =128


< or =1.0


> or =4.0


< or =2.0


> or =8.0


< or =1.0


> or =16


< or =4.0


> or =16


< or =2.0


> or =8


< or =8.0


> or =32


< or =2/38


> or =4/76


< or =1.0


> or =4.0


No interpretations available

Interpretation Provides information to assist in interpretation of the test results

Results are reported as the minimum inhibitory concentration in micrograms/mL.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Brown-Elliott BA, Wallace RJ Jr.: Clinical and taxonomic status of pathogenic nonpigmented or late-pigmenting rapidly growing mycobacteria. Clin Microbiol Rev 2002 October;15:716-746

2. Colombo RE, Olivier KN: Diagnosis and treatment of infections caused by rapidly growing mycobacteria. Semin Respir Crit Care Med 2008 October;29:577-588

3. Kasperbauer SH, DeGroote MA: The treatment of rapidly growing mycobacterial infections. Clin Chest Med 2015 March;336:67-78

Special Instructions and Forms Library of PDFs including pertinent information and consent forms, specimen collection and preparation information, test algorithms, and other information pertinent to test