Background: Pulmonary disease caused by nontuberculous mycobacteria has a variable clinical course. Although this is possibly the result of not only host factors, but also bacterial factors, many questions remain to be answered regarding these manifestations.
Methods: To assess the relationship between the progression of pulmonary Mycobacterium avium disease and bacterial factors we performed variable number tandem repeats (VNTR) typing analysis of M. avium tandem repeats (MATR) in M. avium isolates from 46 patients with different clinical courses, and furthermore, examined the association between disease progression and a pMAH135 plasmid derived from M. avium.
Results: In patients whose treatment was initiated because of worsenedchest radiograph findings and/or clinical symptoms within 18 months after being diagnosed with pulmonary M. avium disease, the detection rate of 6 genes located in pMAH135 was 35.3-47.1% for 17 isolates. However, in untreated patients with a stable condition, these rates were 10.3-13.8% in 29 isolates. MATR-VNTR typing analysis showed that isolates from patients with worsened disease and those with stable disease are clustered differently. In cluster III, the number of isolates from patients with worsened disease was higher than that from patients with stable disease (p = 0.019), and furthermore, the number of isolates carrying pMAH135 genes was higher than that not carrying pMAH135 genes (p ≤ 0.001).
Conclusion: These results indicate an association between the progression of pulmonary M. avium disease and pMAH135. The presence of pMAH135 genes might be a useful prognostic indicator for pulmonary M. avium disease and may serve as one criterion for treatment initiation.