Increased macrolide resistance rate of correlated with epidemic in Beijing, China in 2023.

We collected respiratory specimens from 128 pediatric patients diagnosed with pneumonia in Beijing in late 2023. was detected in 77.3% (99/128) patients, with 36.4% (4/11), 82.9% (34/41), 80.3% (61/76) in children aged less than 3 years, 3-6 years, over 7 years, respectively. () was characterized using P1 gene typing, MLVA typing and sequencing of domain V of the 23S rRNA gene. P1 gene type 1 (P1-1; 76.1%, 54/71) and MLVA type 4-5-7-2 (73.7%, 73/99) were predominant. MLVA identified a new genotype: 3-4-6-2. Macrolide resistance-associated mutations were detected in 100% of samples, with A2063G accounting for 99% and A2064G for 1%. The positive rate of was higher compared to previous reports, especially in children less than 3 years, suggesting a epidemic showing a younger age trend occurred in late 2023 in Beijing, China. Higher proportions of macrolide-resistant , P1-1 and 4-5-7-2 genotype indicated increased macrolide resistance rate and genotyping shift phenomenon, which might be attributable to this epidemic. Additionally, complete clinical information from 73 pneumonia inpatients were analyzed. The incidence of severe pneumonia was 56.2% (41/73). pneumonia patients exhibited longer duration of fever, with a median value of 10.0 days (IQR, 8.0-13.0), and higher incidence of complications (74.0%, 54/73). However, in this cohort, we found that the severity of pneumonia, co-infection, or complications were not associated with P1 gene or MLVA types. Clinicians should be aware that patients infected with macrolide-resistant exhibited more severe clinical presentations.