The Signifi cance of Mycobacterium abscessus Subsp ecies abscessus Isolation during Mycobacterium avium Complex Lung Disease Therapy

Abstract

BACKGROUND: Isolation of Mycobacterium abscessus subspecies abscessus (MAA) is common during Mycobacterium avium complex (MAC) lung disease therapy, but there is limited information about the clinical signifi cance of the MAA isolates. METHODS: We identifi ed 53 of 180 patients (29%) treated for MAC lung disease who had isolation of MAA during MAC lung disease therapy. Patients were divided into those without (group 1) and those with (group 2) MAA lung disease. RESULTS: There were no significant demographic differences between patients with and without MAA isolation or between groups 1 and 2. Group 1 and 2 patients had similar total sputum cultures obtained ( P=.7; 95% CI , - 13.4 to 8.6) and length of follow-up ( P=.8; 95% CI, - 21.5 to 16.1). Group 2 patients had signifi cantly more total positive cultures for MAA (mean ± SD, 15.0 ± 11.1 vs 1.2 ± 0.4; P , .0001; 95% CI, 2 17.7 to 2 9.9), were signifi - cantly more likely to develop new or enlarging cavitary lesions while on MAC therapy ( P < .0001), and were signifi cantly more likely to meet all three American Th oracic Society diagnostic criteria for nontuber culous mycobacterial disease (21 of 21 [100%] vs 0 of 32 [0%]; P < .0001) compared with group 1 patients. Group 1 patients were signifi cantly more likely to have single, positive MAA cultures than group 2 patients (25 of 31 vs 0 of 21; P < .0001). CONCLUSIONS: Microbiologic and clinical follow-up aft er completion of MAC lung disease therapy is required to determine the signifi cance of MAA isolated during MAC lung disease therapy. Single MAA isolates are not likely to be clinically signifi cant.