Analysis of the potentially pathogenic bacteria of lower respiratory tract infections in children per-, during and post-COVID-19: a retrospective study.

Background: The coronavirus disease 2019 (COVID-19) pandemic has caused significant changes in lower respiratory tract infections (LRTIs). This study aimed to characterize potentially pathogenic bacterial infections in paediatric patients hospitalized for LRTIs per-, during and post-COVID-19.

Methods: Sputum culture data from 85,659 children with LRTIs at the Children's Hospital of Soochow University from January 2016 to May 2024 were analyzed for eight bacteria: Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus, Moraxella catarrhalis, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Acinetobacter baumannii. The data during the pandemic (2020-2022, during COVID-19) and after the pandemic (January 2023-May 2024, post-COVID-19) were compared with those before the pandemic (2016-2019).

Results: Overall, 85,659 children with LRTIs were enrolled. Of these, 42,567 cases (49.7%) were diagnosed in the pre-COVID-19 period, 22,531 cases (26.3%) during the COVID-19 period and 20,561 cases (24.0%) in the post-COVID-19 period. The overall positive rate for pathogenic bacteria was 37.1%, with the top three being S. pneumoniae (14.5%), H. influenzae (12.1%) and S. aureus (6.5%). Compared to the average pre-COVID-19 levels, the bacterial pathogen positive rate decreased by 3.5% during the COVID-19 period (OR: 0.94, 95% CI: 0.91-0.98) and by 23.4% in the post-COVID-19 period (OR: 0.66, 95% CI: 0.64-0.69). During the COVID-19 period, the positive rates for S. pneumoniae, H. influenzae, E. coli, K. pneumoniae and mixed infections decreased by 11.7%, 35.3%, 22.2%, 33.3% and 45.7% respectively, while the positive rates for S. aureus, M. catarrhalis and P. aeruginosa increased by 21.7%, 44.7% and 25% respectively. In the post-COVID-19 period, the positive rates for S. pneumoniae, H. influenzae, E. coli, P. aeruginosa, K. pneumoniae, A. baumannii and mixed infections decreased by 50.0%, 7.4%, 22.2%, 50.0%, 44.4%, 60.0% and 32.6% respectively, while there was no statistical change in the positive rates for S. aureus and M. catarrhalis. Bacteria case detection decreases in 2020 (67.0%), 2021 (60.5%), 2022 (76.3%) and 2023 (72.7%) compared to predicted cases.

Conclusions: Measures to restrict COVID-19 as a driver of declining bacterial positive rates. Respiratory bacteria in children are change across COVID-19 phases, age groups and seasons. After COVID-19, clinicians should continue to increase surveillance for pathogenic bacteria, especially drug-resistant flora.