Mycoplasma pneumoniae macrolide resistance acquisition in a CCR2-deficient child.

Since November 2023, an increase in M. pneumoniae respiratory infections has been observed in France. Macrolides are the reference treatment and are indicated as first-line therapy. Macrolide-resistant strains have been described in clinical isolates, especially in Asian countries. In the present manuscript, we report the persistence of an M. pneumoniae strain from an immunocompromised child with CCR2 deficiency on prophylactic azithromycin treatment. Antimicrobial susceptibility testing showed acquisition of macrolide resistance after treatment with azithromycin. Molecular typing using two typing methods revealed the persistence of the same strain over time. This case highlights the need for access to rapid detection tools to determine the causative pathogen and potential antimicrobial resistance mechanisms. This is particularly important for patients with comorbidities receiving prophylactic antibiotics and require additional caution. Acquisition of resistance can lead to complications and extended hospitalisation. Higher molecular resolution would be useful for the detection of putative heteroresistance in M. pneumoniae.