Test ID: MMLNS
Antimicrobial Susceptibility, Nocardia species
Useful For 
Suggests clinical disorders or settings where the test may be helpful
Determining the resistance of species of Nocardia and other aerobic actinomycetes to antimicrobial agents
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Nocardia asteroides, the most commonly recognized aerobic actinomycete, causes significant disease in immunocompromised patients. Clinical presentations can include pneumonia, skin abscess, bacteremia, brain abscess, eye infection, and joint infection. Other species associated with human disease include Nocardia brasiliensis, Nocardia otitidiscaviarum, Nocardia farcinica, Nocardia nova, and Nocardia transvalensis.
Treatment usually consists of trimethoprim-sulfamethoxazole, sometimes in combination with other antimicrobials, such as amikacin. However, some patients develop drug allergy, others develop resistant isolates due to noncompliance, and some antimicrobials penetrate the central nervous system better than others. Therefore, the selection of appropriate agents becomes extremely important to patient outcome.
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.
The following are interpretive values for susceptibility testing of Nocardia species using a broth microdilution method.
| Antimicrobial Agent | Concentration Range mcg/mL | Interpretations | ||
| S | I | R | ||
| Trimethoprim/ Sulfamethoxazole(3) | 0.25/4.75-8/152 | < or =2/38 | - | > or =4/76 |
| Linezolid(2) | 1-32 | < or =8 | - | - |
| Ciprofloxacin | 0.12-4 | < or =1 | 2 | > or =4 |
| Imipenem | 2-64 | < or =4 | 8 | > or =16 |
| Moxifloxacin(1,3) | 0.25-8 | - | - | - |
| Cefepime(3) | 1-32 | < or =8 | 16 | > or =32 |
| Augmentin(3) | 2/1-64/32 | < or =8/4 | 16/8 | > or =32/16 |
| Amikacin | 1-64 | < or =8 | - | > or =16 |
| Ceftriaxone(3) | 4-64 | < or =8 | 16-32 | > or =64 |
| Doxycycline | 0.12-16 | < or =1 | 2-4 | > or =8 |
| Minocycline(3) | 1-8 | < or =1 | 2-4 | > or =8 |
| Tobramycin | 1-16 | < or =4 | 8 | > or =16 |
| Clarithromycin | 0.06-16 | < or =2 | 4 | > or =8 |
Interpretation Provides information to assist in interpretation of the test results
Interpretive values for susceptibility testing of Nocardia species using a broth microdilution method. (Values expressed in mcg/mL):
| Antimicrobial Agent | Interpretations | ||
| S | I | R | |
| Trimethoprim/ Sulfamethoxazole(3) | < or = 2/38 | - | > or =4/76 |
| Linezolid(2) | < or =8 | - | - |
| Ciprofloxacin | < or =1 | 2 | > or =4 |
| Imipenem | < or =4 | 8 | > or =16 |
| Moxifloxacin(1,3) | - | - | - |
| Cefepime(3) | < or =8 | 16 | > or =32 |
| Augmentin(3) | < or =8/4 | 16/8 | > or =32/16 |
| Amikacin | < or =8 | - | > or =16 |
| Ceftriaxone(3) | < or =8 | 16-32 | > or =64 |
| Doxycycline | < or =1 | 2-4 | > or =8 |
| Minocycline(3) | < or =1 | 2-4 | > or =8 |
| Tobramycin | < or =4 | 8 | > or =16 |
| Clarithromycin | < or =2 | 4 | > or =8 |
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
No significant cautionary statements
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Corti ME, Villafane-Fioti MF: Nocardiosis: a review. Int J Infect Dis 2003;7:243-250
2. Saubolle MA, Sussland D: Nocardiosis: review of clinical and laboratory experience. J Clin Microbiol 2003;41:4497-4501
3. Brown-Elliott BA, Brown JM, Conville PS, Wallace RJ Jr: Clinical and laboratory features of the Nocardia species based on current molecular taxonomy. Clin Microbiol Rev 2006;19:259-282
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