In this study, 116 (97.4%) cases had a positive AFB smear, and the smear grades of patients with IR MAB T28 were significantly higher than those of patients with non-IR MAB T28 (P < 0.01). The sequencing analysis of all 119 isolates from each patient identified the following subspecies: MAB (51), MAM (66), and mixed infections with MAB and MAM (2). A total of 119 MABS were classified into three predefined groups according to the IR results: 29 with IR, 77 without IR, and 13 with acquired resistance (Table-Supplementary Material). Among these, 29 isolates with IR were identified 26 MAB T28, 1 MAB C28, and 2 mixed MAB T28 with MAM. Notably, 77 isolates without IR were identified, including 14 MAB T28, 5 MAB C28, and 58 MAM, and the remaining 13 isolates with acquired resistance were 5 MAB T28 and 8 MAM. The rrl sequencing analysis revealed mutations, wherein adenine was replaced by guanine in all eight acquired resistant MAM isolates. In contrast, three MAB T28 isolates failed to show any rrl mutations, and two isolates were concordant with substitutions at positions 2059 (8/8, 100.0% vs. 2/5, 40.0%; P = 0.03).
Among the 119 patients, 22 (18.5%) did not satisfy the sputum microbiological criteria for NTM-PD. Of the 22 patients with non-MABS-PD, 10 had MAB T28, and 12 had MAM. Notably, the percentage of patients with non-MABS-PD with MAB T28 was significantly higher in the non-IR T28 group (6 patients, 42.9%) than in the IR T28 group (4 patients, 12.9%) (P = 0.04). Of the 97 patients meeting the diagnostic criteria for NTM-PD, 12 (12.4%) did not receive antibiotic therapy for the following reasons: mild symptoms and no clear evidence of disease progression during the observation period (n = 5), loss to follow-up (n = 2), transfer to another hospital after the diagnosis of MABS-PD (n = 1), or death due to another disease (n = 4). Of the 12 patients with untreated MABS-PD, 1 patient with IR (MAB T28 + MAM) and 5 non-IR (1 T28, 1 C28, and 3 MAM) achieved spontaneous sputum culture conversion.
The proportion of the 85 patients who received multidrug therapy was significantly lower in the non-IR T28 group (5 patients) than in the IR T28 group (21 patients) (P = 0.04). The radiographic types between the IR and non-IR groups did not differ significantly; however, the sputum culture conversion rate was significantly higher in patients whose isolates in the non-IR group included T28 than in those whose isolates were IR or acquire resistance (4/5, 80.0% vs. 5/21, 23.8% vs. 0/5, 0.0%, respectively; P < 0.01).