Comparing the Genotype and Drug Susceptibilities between Mycobacterium avium and Mycobacterium intracellulare in China

摘要

Objective Mycobacterium avium(M. avium) and Mycobacterium intracellulare(M. intracellulare) are the major causative agents of nontuberculous mycobacteria(NTM)-related pulmonary infections. However, little is known about the differences in drug susceptibility profiles between these two species. Methods A total of 393 NTM isolates were collected from Shanghai Pulmonary Disease Hospital. Sequencing of partial genes was performed to identify the strains at species level. The minimum inhibitory concentration(MIC) was used to evaluate the drug susceptibility against 20 antimicrobial agents. Variable number of tandem repeat(VNTR) typing was conducted to genotype these two species. Results A total of 173(44.0%) M. avium complex(MAC) isolates were identified, including 41(10.4%) M. avium isolates and 132(33.6%) M. intracellulare isolates. Clarithromycin and amikacin were the two most effective agents against MAC isolates. The Hunter-Gaston Discriminatory Index(HGDI) values for VNTR typing of M. avium and M. intracellulare isolates were 0.993 and 0.995, respectively. Levofloxacin resistance was more common among the unclustered strains than among the clustered strains of M. intracellulare. Conclusion M. intracellulare was the most common NTM species in China. Clarithromycin and amikacin had high antimicrobial activities against MAC. VNTR typing of MAC isolates revealed a high discriminatory power. Levofloxacin resistance was associated with unclustered strains of M. intracellulare.