Treatment outcomes and relapse in patients with Mycobacterium avium-intracellulare complex pulmonary disease

The treatment responses and outcomes in patients with Mycobacterium avium-intracellulare complex pulmonary disease (MAC-PD) remain uncertain. This retrospective study was conducted in Taiwan between 2011 and 2020. A microbiological cure was defined as the requirement for a minimum of three consecutive negative cultures following culture conversion that continued until the completion of anti-MAC treatment. A total of 97 patients with MAC-PD were enrolled in this study. The sputum smear-negative conversion rate was 40% (19/47). Thirty (31%) patients achieved sputum culture-negative conversion rates within 3 years after treatment initiation. All patients with negative sputum culture conversion rates achieved microbiological cure. Patients treated with a macrolide + rifamycin + ethambutol (M + R + EMB)-based regimen had a higher microbiological cure rate than the other patients (39% vs 17%, P = 0.023). Patients with persistently positive sputum smears after 6 months of treatment had a lower microbiological cure rate than those with negative sputum smears (6% vs 44%, P < 0.001). Among 30 patients with microbiological cure, the median time from sputum culture conversion to treatment completion was 221.5 (0-483) days, and the 1-year relapse rate was 17%. Treatment with the M + R + EMB-based regimen was associated with a higher microbiological cure rate, and patients with persistently positive sputum smears after 6 months of treatment had a lower microbiological cure rate. IMPORTANCE The treatment responses and outcomes in patients with Mycobacterium avium-intracellulare complex pulmonary disease (MAC-PD) remain uncertain. In this study, patients with MAC-PD treated with a macrolide + rifamycin + ethambutol (M + R + EMB)-based regimen had a higher microbiological cure rate than those treated with other regimens. After 6 months of treatment, patients with persistently positive sputum smears had a lower microbiological cure rate than those with negative sputum smears. Among patients with microbiological cure, the median time from sputum culture conversion to treatment completion was 221.5 days (range, 0-483), and the 1-year relapse rate was 17%.

Long-Term Prognosis and Antimycobacterial Glycolipid Antibody as Biomarker in Mycobacterium avium-intracellulare Complex Pulmonary Disease

Clinical characteristics and outcomes of multidrug chemotherapy have been used as the main prognostic factors for Mycobacterium avium-intracellulare complex pulmonary disease (MAC-PD) over the last decade; however, no useful prognostic biomarkers have been reported. The aim is to ascertain whether the serum antibody titers could include useful prognostic predictors of MAC-PD. Ninety-four patients with MAC-PD were enrolled and regularly followed up with for more than 5 years or until death. Cox proportional hazard regression and receiver operating characteristic (ROC) curve analyses were used to identify predictors of mortality in this prospective observational study. According to treatment outcomes, 85 patients completed follow-up and were classified into four groups. Seventeen patients (20%) died during follow-up (median, 10.1 years; interquartile range, 8.1 to 12.4 years). All 11 patients with MAC-PD-specific death were included in the 14 patients of the group nonresponsive to the multidrug chemotherapy. They had significantly higher anti-Mycobacterium glycolipid (MBGL) antibody titers than those in the other groups and a significantly (P < 0.0001) poorer survival prognosis. The anti-MBGL antibody titers also served as a negative prognostic factor. A cutoff score of 7, which was calculated by clinical poor prognostic characteristics and anti-MBGL antibody titers, differentiated the nonresponse group and the other groups at baseline (sensitivity, specificity, and area under the curve: 92.9%, 81.7%, and 0.95, respectively). In conclusion, anti-MBGL antibody titers were useful to assess the refractory MAC-PD. The predictions of treatment outcome and mortality become more accurate by using anti-MBGL antibody and clinical poor prognostic characteristics together. IMPORTANCE The natural history of MAC-PD is challenging to predict in immunocompetent patients at diagnosis, and the current multidrug chemotherapy options are not strong enough to eliminate mycobacteria from the lungs. Therefore, the diagnosis of MAC-PD does not necessarily lead to the decision to start chemotherapy. We have also observed refractory patients in clinical practice, who were resistant to multiple-drug chemotherapy and showed persistent excretion of MAC bacilli and progressive worsening of chest radiographic findings until death. We have reported that the measurements of anti-MBGL antibody titers helped assess refractory MAC-PD in this study. Furthermore, the predictions of treatment outcome and mortality become more accurate by using the anti-MBGL antibody in addition to clinical poor prognostic characteristics, which were older age, lower body mass index, the positive results of a smear test for acid-fast bacteria (AFB), and presence of cavitary disease.