Relationship Between Clarithromycin Minimum Inhibitory Concentrations and Treatment Responses in Mycobacterium avium...

Area of Science:

• Pulmonology
• Infectious Diseases
• Clinical Microbiology

Background:

• Mycobacterium avium complex pulmonary disease (MAC-PD) is a growing global health concern.
• Macrolides are essential for treating progressive MAC-PD, but their effectiveness is influenced by minimum inhibitory concentrations (MICs).
• The impact of clarithromycin MICs, particularly within the susceptible range, on treatment outcomes for MAC-PD is not well understood.

Purpose of the Study:

• To investigate the association between clarithromycin minimum inhibitory concentrations (MICs) and microbiological cure rates in patients with pulmonary disease caused by Mycobacterium avium complex (MAC-PD).
• To determine if clarithromycin MICs within the susceptible range affect treatment response in MAC-PD.
• To evaluate the impact of high clarithromycin MICs on treatment outcomes.

Main Methods:

• Retrospective analysis of adult patients treated for MAC-PD between March 2009 and March 2022.
• Categorization of patients into four groups based on clarithromycin MICs of causative strains at treatment initiation.
• Logistic regression analysis, adjusting for clinical factors and companion drug MICs, to assess the impact of clarithromycin MICs on microbiological cure.

Main Results:

• Microbiological cure rates were 51.8% (MIC ≤0.5 µg/mL), 51.9% (MIC 1-2 µg/mL), 50.0% (MIC 4-8 µg/mL), and 18.2% (MIC ≥32 µg/mL).
• No significant difference in cure rates was found for clarithromycin MICs within the susceptible range (≤8 µg/mL).
• Patients with MICs ≥32 µg/mL had a significantly lower odds ratio (0.25) for microbiological cure compared to susceptible strains (P=0.06).

Conclusions:

• Clarithromycin treatment response is comparable across susceptible MIC ranges for MAC-PD.
• Higher clarithromycin MICs (≥32 µg/mL) are associated with poorer treatment outcomes in MAC-PD.
• These findings highlight the importance of considering clarithromycin MICs for optimizing MAC-PD treatment strategies.