title: Clinical significance of differentiation of Mycobacterium massiliense from Mycobacterium abscessus.
abstract: BACKGROUND
  Mycobacterium massiliense has been recognized as a separate species from Mycobacterium abscessus; however, little is known regarding the clinical impact of this differentiation.
  
  
  OBJECTIVE
  To compare clinical features and treatment outcomes between patients with M. abscessus lung disease and those with M. massiliense lung disease.
  
  
  METHODS
  We performed molecular identification of stored clinical isolates of M. abscessus complex and compared clinical characteristics and treatment outcomes between 64 patients with M. abscessus lung disease and 81 patients with M. massiliense lung disease.
  
  
  RESULTS
  The clinical and radiographic manifestations of disease caused by each species were similar. Standardized combination antibiotic therapy, including a clarithromycin-containing regimen in combination with an initial 4-week course of cefoxitin and amikacin, was given to 57 patients (24 with M. abscessus and 33 with M. massiliense) for more than 12 months. The proportion of patients with sputum conversion and maintenance of negative sputum cultures was higher in patients with M. massiliense infection (88%) than in those with M. abscessus infection (25%; P < 0.001). Inducible resistance to clarithromycin (minimal inhibitory concentrations ≥ 32 μg/ml) was found in all tested M. abscessus isolates (n = 19), but in none of the M. massiliense isolates (n = 28).
  
  
  CONCLUSIONS
  Treatment response rates to combination antibiotic therapy including clarithromycin were much higher in patients with M. massiliense lung disease than in those with M. abscessus lung disease. The inducible resistance to clarithromycin could explain the lack of efficacy of clarithromycin-containing antibiotic therapy against M. abscessus lung disease.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
authors.forename: Won-Jung
authors.initials: WJ
authors.lastname: Koh
authors.forename: Kyeongman
authors.initials: K
authors.lastname: Jeon
authors.forename: Nam Yong
authors.initials: NY
authors.lastname: Lee
authors.forename: Bum-Joon
authors.initials: BJ
authors.lastname: Kim
authors.forename: Yoon-Hoh
authors.initials: YH
authors.lastname: Kook
authors.forename: Seung-Heon
authors.initials: SH
authors.lastname: Lee
authors.forename: Young Kil
authors.initials: YK
authors.lastname: Park
authors.forename: Chang Ki
authors.initials: CK
authors.lastname: Kim
authors.forename: Sung Jae
authors.initials: SJ
authors.lastname: Shin
authors.forename: Gwen A
authors.initials: GA
authors.lastname: Huitt
authors.forename: Charles L
authors.initials: CL
authors.lastname: Daley
authors.forename: O Jung
authors.initials: OJ
authors.lastname: Kwon
mesh_terms: D000583:Amikacin / Q000627:therapeutic use; D000904:Antibiotics, Antitubercular / Q000627:therapeutic use; D002440:Cefoxitin / Q000627:therapeutic use; D017291:Clarithromycin / Q000627:therapeutic use; D024881:Drug Resistance, Bacterial; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D009165:Mycobacterium Infections, Nontuberculous / Q000175:diagnosis / Q000188:drug therapy / Q000382:microbiology*; D009170:Nontuberculous Mycobacteria / Q000187:drug effects; D012189:Retrospective Studies; D013183:Sputum / Q000382:microbiology; D016896:Treatment Outcome
chemical_list: D000904:Antibiotics, Antitubercular; D002440:Cefoxitin; D000583:Amikacin; D017291:Clarithromycin