Etiological characteristics of Mycoplasma pneumoniae infection and macrolide resistance in children in beijing: a retrospective study from 2018 to 2024.

Background: Mycoplasma pneumoniae (MP) is a major cause of pediatric respiratory tract infections (RTIs), with recent increases in incidence and macrolide resistance. The epidemiology of MP, macrolide-resistant MP (MRMP), co-infection patterns, and their relationship with disease severity in the post-COVID era remain poorly understood. We analyzed temporal trends in MP infection and MRMP prevalence and assessed their association with severe community-acquired pneumonia (SCAP).

Methods: Children aged < 18 years hospitalized with RTIs at Beijing Children's Hospital were retrospectively enrolled during 2018-2024. Respiratory samples were tested for MP and macrolide resistance mutations. Data on co-infecting bacterial and viral pathogens were collected in clinical practice and retrospectively included in this study. We analyzed temporal trends and risk factors for SCAP.

Results: Among 8,453 children, MP-positive patients accounted for 39.7%, declining to 17.0% in 2021 and rising sharply to 62.8% in 2024. The highest MP-positivity rates were seen in children aged 5-9 years, although a notable increase occurred in children aged < 5 years in 2024. MRMP was detected in 96.9% of MP-positive cases, with resistance rates > 95% from 2022. After 2021, co-infections were detected in 19.9% of cases tested for bacterial and viral pathogens, most commonly involving human rhinovirus-MP, Haemophilus influenzae-MP, and Streptococcus pneumoniae-MP. Risk factors for SCAP included female sex, age > 5 years, cold season onset, pure MP infection, and MP co-infection. MRMP was not an independent predictor of SCAP.

Conclusions: The burden of MP infection has resurged post-COVID, with sustained high macrolide resistance and evolving co-infection patterns. Our findings underscore the importance of ongoing surveillance and tailored management strategies for pediatric MP infections.