Whole genome sequencing confirmed the de novo development of macrolide resistance in a child with Mycoplasma pneumoniae infection receiving azithromycin treatment

A child undergoing azithromycin treatment for Mycoplasma pneumoniae infection developed macrolide resistance de novo. The patient initially presented with respiratory symptoms, and despite standard macrolide therapy, clinical improvement was not sustained. Whole genome sequencing (WGS) of Mycoplasma pneumoniae isolates, collected before and after treatment, confirmed the emergence of macrolide resistance, specifically identifying a 23S rRNA A2063G mutation. This genetic change was not present in the initial isolate but was detected in the post-treatment sample, directly linking the treatment to resistance development. The case highlights the importance of monitoring for acquired resistance during antimicrobial therapy, especially in pediatric populations.