Drug resistance and molecular epidemiology of pediatric Mycoplasma pneumoniae isolates in Southern China

To investigate antimicrobial susceptibility and molecular typing of recent pediatric Mycoplasma pneumoniae strains, analyze the correlations between drug resistance, pneumonia severity, and strain types, and provide evidence for precise M. pneumoniae infection management. Standard M. pneumoniae isolation and culture were applied to bronchoalveolar lavage fluid from 325 M. pneumoniae -infected children, with 23S rRNA resistance mutation detection. Antimicrobial susceptibility testing (eight antibiotics, microbroth dilution) was performed on 154 culture-positive strains, alongside multiple locus variable-number tandem repeat analysis (MLVA), whole-genome sequencing, and single-nucleotide polymorphism (SNP) genotyping. M. pneumoniae showed high macrolide resistance (99.35% for erythromycin and azithromycin), but high susceptibility to moxifloxacin/levofloxacin, with minocycline/doxycycline sensitivity at 98.71%. The 23S rRNA mutations occurred in 97.4% (150/154). MLVA type 4-5-7-2 dominated (135/154), with minor types totaling 15 cases. SNP typing clustered strains into four groups, mostly EC1 (138/154), with four genes showing cross-cluster mutations. Southern Chinese M. pneumoniae strains exhibit high macrolide resistance but good minocycline/doxycycline susceptibility, with EC1-cluster dominance driving rapid spread. This supports individualized therapy and epidemic trend tracking for pediatric M. pneumoniae lung infections. IMPORTANCE This study sheds light on why many children with Mycoplasma pneumoniae pneumonia do not respond well to common macrolide antibiotics—over 99% of strains in Southern China are resistant. It identifies effective alternative drugs and pinpoints the dominant spreading strain, helping doctors choose precise treatments. For public health, it provides key data to track outbreaks, guiding targeted surveillance and better management of pediatric respiratory infections post-COVID-19.