title: Species identification of Mycobacterium abscessus subsp. abscessus and Mycobacterium abscessus subsp. bolletii using rpoB and hsp65, and susceptibility testing to eight antibiotics.
abstract: OBJECTIVE
  To separate Mycobacterium abscessus subsp. bolletii from Mycobacterium abscessus subsp. abscessus using species identification, and to investigate the in vitro activity of amikacin, cefoxitin, imipenem, levofloxacin, moxifloxacin, clarithromycin, azithromycin, and linezolid against Mycobacterium abscessus.
  
  
  METHODS
  Seventy M. abscessus isolates, previously identified by 16S rRNA sequencing, were further identified by comparative sequence analysis of rpoB and hsp65. Drug susceptibility testing was conducted using the microplate Alamar Blue assay in accordance with Clinical and Laboratory Standards Institute (CLSI) guidelines and interpreted using CLSI breakpoints.
  
  
  RESULTS
  Of the 70 strains, 45 (64%) were M. abscessus subsp. abscessus and 25 (36%) were M. abscessus subsp. bolletii. The majority of M. abscessus isolates were susceptible to azithromycin, amikacin, linezolid, and imipenem (M. abscessus subsp. abscessus: 93%, 98%, 93%, and 73%, respectively; M. abscessus subsp. bolletii: 96%, 96%, 80%, and 68%, respectively). Approximately half of the M. abscessus isolates were moderately susceptible to cefoxitin and moxifloxacin (M. abscessus subsp. abscessus 53% and 49%; M. abscessus subsp. bolletii 72% and 68%). Nearly all the M. abscessus isolates were resistant to levofloxacin (M. abscessus subsp. abscessus 96%, M. abscessus subsp. bolletii 100%). Inducible clarithromycin resistance was found in M. abscessus. After 14 days of incubation, 83% M. abscessus subsp. abscessus and 36% M. abscessus subsp. bolletii were resistant to clarithromycin.
  
  
  CONCLUSIONS
  Using rpoB and hsp65, M. abscessus subsp. bolletii could be distinguished from M. abscessus subsp. abscessus. Amikacin and azithromycin showed excellent activity against M. abscessus in vitro. Imipenem, linezolid, cefoxitin, and moxifloxacin also showed good activity. Levofloxacin was inactive against M. abscessus. Although clarithromycin showed excellent activity against M. abscessus on day 3, inducible resistance occurred, and after 14 days clarithromycin showed little activity against M. abscessus subsp. abscessus, but still had good activity against M. abscessus subsp. bolletii.
authors.affiliation: Department of Tuberculosis, Beijing Chest Hospital, Capital Medical University, Tongzhou District, Beijing, PR China.
authors.forename: Wenjuan
authors.initials: W
authors.lastname: Nie
authors.affiliation: Department of Tuberculosis, Beijing Chest Hospital, Capital Medical University, Tongzhou District, Beijing, PR China.
authors.forename: Hongfei
authors.initials: H
authors.lastname: Duan
authors.affiliation: Reference Laboratory, Beijing Chest Hospital, Capital Medical University, Tongzhou District, Beijing, PR China.
authors.forename: Hairong
authors.initials: H
authors.lastname: Huang
authors.affiliation: Department of Pharmacology, Beijing Chest Hospital, Capital Medical University, Tongzhou District, Beijing, PR China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Lu
authors.affiliation: Department of Internal Medicine, The Second People's Hospital of Jinan, Huaiyin District, Jinan City, Shandong Province, PR China.
authors.forename: Dapeng
authors.initials: D
authors.lastname: Bi
authors.affiliation: Department of Tuberculosis, Beijing Chest Hospital, Capital Medical University, Tongzhou District, Beijing, PR China. Electronic address: dongchu1994@sina.com.
authors.forename: Naihui
authors.initials: N
authors.lastname: Chu
mesh_terms: D000904:Antibiotics, Antitubercular / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics*; D018834:Chaperonin 60 / Q000235:genetics*; D060005:Genotyping Techniques; D006801:Humans; D008826:Microbial Sensitivity Tests; D009165:Mycobacterium Infections, Nontuberculous / Q000382:microbiology*; D009170:Nontuberculous Mycobacteria / Q000145:classification / Q000187:drug effects* / Q000235:genetics* / Q000254:growth & development; D010641:Phenotype; D016133:Polymerase Chain Reaction; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D013183:Sputum / Q000382:microbiology
chemical_list: D000904:Antibiotics, Antitubercular; D001426:Bacterial Proteins; D018834:Chaperonin 60; D012336:RNA, Ribosomal, 16S; C074119:heat-shock protein 65, Mycobacterium
keywords: Clarithromycin; Inducible resistance; Mycobacterium abscessus subsp. abscessus; Mycobacterium abscessus subsp. bolletii; Susceptibility testing