Analysis of distribution characteristics of clinical isolates of nontuberculous mycobacteria in a general hospital

Abstract

Objective To investigate the current prevalence of nontuberculous mycobacteria (NTM) in Shanghai, and to study the distribution characteristics of NTM clinical isolates, which may help to improve the diagnostic level of NTM and provide guidance for effective prevention and treatment of NTM infection. Methods Culture-positive isolates of clinical mycobacteria were collected from 2008 to 2013 in Huashan Hospital affiliated to Fudan University. All isolates were heat inactivated, and the genomic DNA was extracted and the species were identified by comprehensive comparative analysis of 16S rDNA, hsp65 and rpoB target genes sequencing. Results From January 2008 to December 2013, the overall mycobacterial culture-positive rate was 4.1% (411/10 015). After excluding the repeated isolates, a total of 253 culture-positive mycobacteria isolates were collected for the species identification. By genes sequencing analysis, 140 isolates were identified as mycobacterium tuberculosis complex (MTBc), 102 NTM and 11 Nocardias, accounting for 55.3%, 40.3% and 4.4%, respectively. Positive rate of NTM isolates had an increasing trend from 25.0% in 2008 to 42.7% in 2013, reaching a highest rate of 54.9% in 2012. In further analysis of 102 NTM isolates, 16 species were identified. Among them, 28 were M. abscesses, 18 strains of M. marinum, 17 strains of M. avium-intracellulare complex and 10 strains of M. fortuitum, accounted for 27.5%, 17.6%, 16.7% and 9.8%, respectively. Conclusions Both of the isolation number and isolation rate of NTM in the general hospital are increasing. NTM related cases are also increasing in recent years, which mainly caused by M. abscess, M. marinum, M. avium-intracellulare complex and M. fortuitum. Key words: Nontuberculous mycobacterium; Target gene sequencing; Species identification; Distribution type