Association of Antimicrobial Susceptibility with Treatment Response in Mycobacterium avium complex Pulmonary Disease

Understanding the clinical implications of minimum inhibitory concentration (MIC) may facilitate optimal drug selection in Mycobacterium avium complex pulmonary disease (MAC-PD) treatment. This study aimed to investigate the association of individual MICs with treatment response of MAC-PD. A retrospective cohort study was conducted in China, including eligible patients diagnosed with MAC-PD between 2018 and 2021. Treatment success rates were calculated across different MIC levels in a subgroup of patients receiving relatively uniform regimens. Associations between MICs and treatment outcomes were investigated by logistic regression analysis. In total, 209 patients with confirmed MAC-PD and initiated treatment were included. The median age was 60.0 years. Among 155 patients who completed treatment, 67.1% achieved treatment success. The treatment success rate was low in patients with clarithromycin MIC ≥ 64 mg/L (25.0%, 1/4) or ethambutol MIC > 16 mg/L (42.9%, 3/7), while remaining relatively stable (75-100%) at other MIC levels. Univariate analyses showed that clarithromycin and ethambutol MICs above these thresholds were associated with increased risk of treatment failure. Our findings suggest an association between clarithromycin MICs and treatment outcomes in patients with MAC-PD receiving standard guideline-recommended regimens. Meanwhile, elevated ethambutol MICs exhibited potential clinical relevance, warranting further investigation.