Clnico-microbiological analysis of mycobacaterium abscessus complex in Japan

Background: The reports on three subspecies of M. abscesses have been increasing in recent years. While macrolide containing regimens are associated with poor reponse to M.abscessus (subsp. abscessus ) and M. bolletii (subsp. bolletii ), M.massiliense (subsp. massiliense ) shows relatively favorable oucome. This clinical inconsistency within subspecies is mainly due to erm gene activation. However, there are a few data analysing clinico-microbiological interrelations about Japanese patients. Methods: A total of 103 M. abscessus stains from 84 patients through 2003 to 2014 at Fukujuji Hospital were identified using rpoB sequenced analysis. The drug ssceptibility testing was performed following CLSI M24-A2. Point mutation at 28 in erm gene and at 2058 in 23S rRNA were analysed by pyrosequencing. Results: rp o B sequence analysis identified 47 M.abscessus (56%), 35 M.massiliense (42%), and 2 M. bolletii (2%). While all M.abscessus and M.bolletii strains were resistant to clarithromycin (CAM) (MIC ≥8)except for three strains that two of them have C28, only one M.massiliense strains holding point mutation at position 2058 in 23S rRNA was resistant to CAM. No significant difference was observed on patients9 clinical manifestations (age, p=0. 347, gender, p=0. 158, radiological findings, p=0.796) between cases of M.abscessus (30 cases) and M.massiliense (29 cases). Eight M. abscessus cases died, while only two mortal cases in M.massiliense , but due to other diseases (p Conclusion: This study showed difficulty in subspecies classification of M.abscessus by clinical presentations. Proper identification and susceptibility testing shall be warranted in routine clinical settings.