Clinical features and treatment outcomes of Mycobacterium chimaera lung disease and antimicrobial susceptibility of the mycobacterial isolates.

BACKGROUND:Mycobacterium chimaera, one of the Mycobacterium avium complex (MAC) members, was recently identified using modern gene sequencing analysis. Unlike M. avium and M. intracellulare, little is known about the clinical features, antimicrobial susceptibilities, and treatment outcomes of M. chimaera lung disease. METHODS:This study was conducted in a medical center from December 2012 to July 2015. Patients who fulfilled the 2007 ATS/IDSA diagnostic criteria for nontuberculous mycobacterial lung disease were enrolled. M. chimaera isolates were identified based on the findings of sequencing of rpoB gene, the internal transcribed spacer (ITS) region of the 16S-23S rRNA gene, and the heat-shock protein 65 gene (hsp65). Minimum inhibitory concentrations (MICs) of 13 antimicrobial agents were determined. RESULTS:During the study period, 247 patients with MAC lung disease were identified, and 11.3% (28/247) of the patients had lung disease caused by M. chimaera. Among these patients, 17 (60.7%) were female, and their median age was 72.5 (40-100) years. All M. chimaera isolates were susceptible to clarithromycin and rifabutin. All the isolates were resistant to moxifloxacin and only 10 (35.7%) and 2 (7.1%) were susceptible to amikacin and linezolid, respectively. Of the nine patients who received macrolide-based regimens, more achieved radiographic resolution than those treated with non-macrolide-based regimens (66.7% vs. 15.8%, P = 0.013), and they tended to have better survival (P = 0.10). CONCLUSIONS:A substantial portion (11.3%) of MAC lung disease cases were caused by M. chimaera, and treatment with macrolide-based regimens resulted in better clinical outcomes for patients with M. chimaera lung disease.