Frequency and clinical relevance of rapidly growing mycobacterium isolated from respiratory samples

Abstract

To assess the frequency and clinical relevance of rapidly growing mycobacterium (RGM) isolates in a tuberculosis referral center in Beijing, China. All isolates were identified by using targeted gene sequencing. RESULTS of species identification for 228 nontuberculous Mycobacterium (NTM) isolates from respiratory samples were analyzed, and available medical files of patients from whom NTM were isolated were reviewed retrospectively. Diagnostic criteria for RGM pulmonary disease issued by the American Thoracic Society (ATS) were used to determine clinical relevance. Isolates of Mycobacterium abscessus (M.abscessus) and Mycobacterium fortuitum (M.fortuitum) accounted for 28.9% (66 isolates) and 8.8% (20 isolates)of NTM isolates, respectively. Sixty-six M. abscessus isolates from 32 patients had evaluable medical files, including 28 cases diagnosed as definite M. abscessus lung disease, and 4 as probable M. abscessus lung disease. Eight M. fortuitum isolates from 8 cases had evaluable medical files, and all of them were diagnosed as unlikely lung disease. Mycobacteria Growth Indicator Tube (MGIT) was more effective to diagnose M. abscessus lung disease, as compared with Lowestein-Jensen medium (23/24 vs 18/28). RGM is a common NTM in our institute. M. abscessus is mostly associated with RGM lung disease, but M. fortuitum is not.