Clinical Implications of Time to Culture Conversion in Mycobacterium Avium Complex Pulmonary Disease

The optimal timing for assessing treatment response in Mycobacterium avium complex pulmonary disease (MAC-PD) remains unclear. This study evaluated the association between time to culture conversion and microbiological cure.

We retrospectively included MAC-PD patients treated at Seoul National University Hospital between January 2011 and April 2024 who achieved culture conversion within 12 months of treatment initiation. Patients were categorized by time to culture conversion: 0-30, 31-60, 61-90, 91-180, and 181-360 days. Multivariable logistic regression was used to assess the impact of conversion timing on microbiological cure.

Among 440 patients, 294 (66.8%) achieved microbiological cure. Compared with those who converted within 30 days, patients who converted at 91-180 days (adjusted odds ratio [aOR], 0.45; 95% CI, 0.24-.87; P = .017) and 181-360 days (aOR, 0.29; 95% CI, .14-.61; P = .001) were significantly less likely to achieve cure. No significant differences were observed for patients converting at 31-60 days (aOR, 1.02; P = .951) or 61-90 days (aOR, 1.19; P = .664), compared with the reference group.

Failure to achieve culture conversion within 90 days was associated with a significantly lower likelihood of microbiological cure. These findings support the need for timely reassessment and potential modification of treatment strategies in patients who remain culture-positive beyond 90 days.