Implications of Intravenous and Inhaled Amikacin Breakpoint Reporting for Mycobacterium avium Complex Pulmonary
Christian M Gill1,2,3,4, Robin Chamberland5,6, Getahun Abate3
1Department of Pharmacy, SSM Health Saint Louis University Hospital, Saint Louis, MO 63104, USA.
Abstract:
The treatment of Mycobacterium avium complex (MAC) remains a clinical challenge as multidrug regimens are needed and may be limited by treatment-related toxicity. The Clinical and Laboratory Standards Institute (CLSI) endorses breakpoints for several agents used for MAC infection treatment. Amikacin has distinct breakpoints for intravenous (IV) therapy and inhaled therapy using amikacin liposome inhalation suspension (ALIS) for MAC pulmonary disease. The purpose of the present retrospective cohort study of MAC pulmonary isolates was to assess the number of amikacin non-susceptible isolates by the IV breakpoints that remain susceptible to the inhaled breakpoints. One isolate per patient per year was assessed and susceptibility was described for amikacin IV, amikacin inhaled, clarithromycin, moxifloxacin, and linezolid per the CLSI. Of the 218 isolates, 94% [204/218] tested as susceptible to amikacin per the IV breakpoints compared with 99.5% [217/218] to the inhaled breakpoints. Of the amikacin IV non-susceptible isolates, 93% [13/14] were susceptible by the inhaled breakpoints. For comparison, clarithromycin was the next most active agent followed by moxifloxacin and linezolid with 97% [211/218], 82% [178/218], and 66% [143/218] of isolates testing as susceptible to each, respectively. These data highlight the importance of laboratories to report both the IV and inhaled amikacin interpretive criteria so that clinicians do not disregard potential therapeutic options for the treatment of MAC pulmonary disease.
Insights
Inhaled amikacin demonstrates higher susceptibility rates for Mycobacterium avium complex (MAC) pulmonary disease compared to intravenous amikacin. This finding is crucial for optimizing MAC treatment strategies.
Area of Science:
- Pulmonary Medicine
- Infectious Diseases
- Clinical Microbiology
Background:
- Treatment of Mycobacterium avium complex (MAC) pulmonary disease is challenging due to multidrug regimens and potential toxicity.
- Clinical and Laboratory Standards Institute (CLSI) provides breakpoints for MAC treatment agents, including distinct criteria for intravenous (IV) and inhaled amikacin.
Purpose of the Study:
- To evaluate amikacin susceptibility in MAC pulmonary isolates using both IV and inhaled therapy breakpoints.
- To determine the proportion of amikacin-non-susceptible isolates (by IV breakpoints) that remain susceptible to inhaled amikacin.
Main Methods:
- Retrospective cohort study of MAC pulmonary isolates.
- Susceptibility testing for amikacin (IV and inhaled), clarithromycin, moxifloxacin, and linezolid according to CLSI guidelines.
- One isolate per patient per year was analyzed.
Main Results:
- 99.5% of isolates were susceptible to inhaled amikacin compared to 94% for IV amikacin.
- 93% of isolates non-susceptible to IV amikacin remained susceptible to inhaled amikacin.
- Susceptibility rates for other agents: clarithromycin (97%), moxifloxacin (82%), and linezolid (66%).
Conclusions:
- Inhaled amikacin exhibits higher susceptibility rates in MAC pulmonary isolates than IV amikacin.
- Laboratories should report both IV and inhaled amikacin susceptibility criteria to guide treatment decisions.
- This distinction is vital to prevent overlooking potential therapeutic amikacin options for MAC pulmonary disease.
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