Minimum inhibitory concentration distributions for Mycobacterium avium complex-towards evidence-based susceptibility
Thomas Schön1, Erja Chryssanthou2
1Department of Clinical Microbiology and Infectious Diseases, Kalmar County Hospital, 391 85 Kalmar, Sweden; Department of Clinical and Experimental Medicine (IKE), Division of Medical Microbiology, Linköping University, Linköping, Sweden.
Summary
Minimum inhibitory concentration (MIC) distributions for Mycobacterium avium complex (MAC) infections were established. High MICs for key drugs suggest current susceptibility breakpoints may not correlate with clinical efficacy.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Mycobacterium avium complex (MAC) infections have suboptimal cure rates with current treatments.
- Correlation between drug susceptibility testing (DST) and clinical outcomes is poor for non-macrolide drugs.
- Systematic evaluation of clinical breakpoints for MAC is lacking.
Purpose of the Study:
- To establish minimum inhibitory concentration (MIC) distributions for MAC.
- To provide data for evaluating clinical breakpoints of antimicrobial agents against MAC.
Main Methods:
- Determined MICs for major anti-MAC drugs using 229 clinical MAC isolates.
- Utilized cation-adjusted Mueller-Hinton II broth for MIC testing.
Main Results:
- Established MIC50 and MIC ranges for clarithromycin, rifabutin, ethambutol, amikacin, moxifloxacin, linezolid, rifampicin, and trimethoprim-sulfamethoxazole.
- Compared obtained MICs with existing susceptibility breakpoints.
Conclusions:
- High MICs observed for rifabutin, rifampicin, ethambutol, linezolid, and moxifloxacin against MAC.
- Current dosing and susceptibility breakpoints may not align with clinical efficacy for these drugs.
- This finding may explain poor DST-clinical outcome correlation in MAC infections.
Keywords:
AmikacinAntimicrobial susceptibility breakpointsClarithromycinEpidemiological cut-off value (ECOFF)RifampicinSulfamethoxazole
