In vitro antimicrobial susceptibility of Mycoplasma pneumoniae and mechanism of macrolide resistance for isolates obtained in Shanghai from 2005 to 2008 / 中华微生物学和免疫学杂志

ABSTRACT

Objective To learn the current in vitro antimicrobial susceptibility of Mycoplasma pneu-moniae in Shanghai and to understand the mechanisms of resistance to macrolides. Methods M. pneumoniae was isolated from pediatric patients with low respiratory tract infections(RTI) using broth and PPLO agar medi-um. PCR amplification and sequence analysis of P1 adhesion gene were performed to identify all M. pneumoniae strains. Susceptibility testing was carried out for macrolides, tetracyclines and fluoroquinolones using broth mi-crodilution method with SP4 broth. PCR amplification and sequence analysis of 23S rRNA genes were performed for all M. pneumoniae strains. P1 gene PCR-RFLP typing was performed to subtype the M. pneumoniae strains. Results One hundred and two M. pneumoniae strains were isolated in Shanghai from Oct 2005 to Dec 2008. All M. pneumoniae isolates were susceptible to the tetracyclines and fluoroquinolones tested. Of 102 clinical isolates, 83(81.4%) was resistant to erytbromycin and all 83 erythromycin-resistant strains had MIC>128 mg/L. An increasing trend of resistance rates were showed 16.7% (1/6) in 2005, 76.5% (13/17) in 2006, 100.0% (24/24) in 2007 and 81.8% (45/55) in 2008. All macrolide-resistant M. pneumoniae strains harbored an A2063G transition mutation in domain V of 23S rRNA genes. The P1 gene RFLP type 1 is predominant (85.3%, 87/102) in M. pneumoniae clinical isolates. Conclusion The macrolide resistance rate of M. pneu-moniae is very high in Shanghai. The mechanism of macrolide resistance is associated with transition mutation on the 23S rRNA gene.