In vitro antimicrobial susceptibility of Mycoplasma pneumoniae isolates across different regions of China in 2023

Objectives To analyse the in vitro antimicrobial susceptibility of Mycoplasma pneumoniae (M. pneumoniae) isolates from 10 different provinces/municipalities across China during the 2023 epidemic. Methods We collected respiratory specimens from paediatric patients diagnosed with M. pneumoniae pneumonia from 10 different provinces/municipalities including Beijing, Shanghai, Liaoning, Gansu, Shanxi, Henan, Hunan, Jiangsu, Guangxi and Guangdong across China from October to December 2023. M. pneumoniae was isolated and cultured from these specimens. Macrolide resistance-associated mutations A2063G or A2064G in the 23S rRNA gene were detected. Minimum inhibitory concentrations (MICs) of five antibiotics (erythromycin, azithromycin, tetracycline, moxifloxacin and doxycycline) were determined using PPLO broth and microdilution susceptibility tests. Results A total of 190 M. pneumoniae isolates were analysed. All isolates harboured the A2063G mutation. All isolates (100%) were highly resistant to erythromycin (MIC range: 128–1024 mg/L) and azithromycin (MIC range: 4–256 mg/L), but susceptible to tetracycline (MIC range: ≤0.125–1 mg/L), doxycycline (MIC range: ≤0.125–1 mg/L) and moxifloxacin (MIC range: ≤0.125 mg/L). For azithromycin and tetracycline, M. pneumoniae isolates from different regions of China showed different susceptibilities. The MICs of tetracycline against M. pneumoniae from northern China were significantly lower than those from central China and southern China. Comparisons among provinces/municipalities suggested that isolates from Hunan and Beijing were more resistant to azithromycin. For tetracycline, the MICs were significantly lower among isolates from Beijing. Conclusions During the 2023 epidemic, isolates of M. pneumoniae were highly resistant to macrolides but remained susceptible to tetracycline and quinolones. For the treatment of macrolide-resistant M. pneumoniae, tetracycline, moxifloxacin and doxycycline would be the recommended antibiotics based on our findings.