Jing Wang,1 Renyan Wang,1 Chunmei Jing,2 Yupei Xiang,3 Zhongzheng Xiong,4 Fang Liu1 

1Department of Clinical Laboratory, Chongqing Red Cross Hospital (People’s Hospital of Jiangbei District), Chongqing, People’s Republic of China; 2Department of Clinical Laboratory, Children’s Hospital of Chongqing Medical University, Chongqing, People’s Republic of China; 3Chongqing JiuLongpo District Science City People’s Hospital, Chongqing, People’s Republic of China; 4Dianjiang People’s Hospital of Chongqing, Chongqing, People’s Republic of China

Correspondence: Fang Liu, Email liufangshuo@126.com

Objective: To comprehensively investigate the epidemiology and analyze the antimicrobial resistance of Haemophilus influenzae isolated from children in Chongqing before, during, and after the COVID-19 pandemic.
Methods: A total of 21,723 Haemophilus influenzae strains from four Chongqing hospitals during 2019– 2024 were included. Antimicrobial susceptibility testing was conducted according to Clinical and Laboratory Standards Institute 2024 breakpoints using Kirby-Bauer method or automated systems. β-lactamase was detected by the cefinase disc method. Specimen types, age-and season-specific distributions, and antibiotic susceptibility results were analyzed.
Results: Among the isolates, 91.43% of infected children were under 6 years old and 57.30% were male. Sputum was the main source (94.22%). Detection rates were higher in spring and winter (p < 0.001). β-lactamase-positive strains accounted for 71.82% and BLNAR strains accounted for 4.99%. High resistance was found for ampicillin (79.05%), cefuroxime (58.95%), ampicillin-sulbactam (59.82%), sulfamethoxazole-trimethoprim (68.51%), azithromycin (49.67%), and cefixime (37.78%), while meropenem (0.48%), levofloxacin (0.11%), chloramphenicol (4.85%), ceftriaxone (0.62%), rifampicin (0.15%), tetracycline (5.55%), and cefepime (6.11%) showed low resistance. The COVID-19 pandemic affected resistance patterns: resistance to ampicillin, aztreonam, cefuroxime, amoxycillin-clavulanic, and ampicillin-sulbactam were higher before and after the COVID-19 pandemic than during it (p< 0.001). Throughout the pre-pandemic, pandemic, and post-pandemic periods, the resistance rates of sulfamethoxazole-trimethoprim cefixime and cefepime showed a downward trend, while the resistance rate of azithromycin showed an upward trend.
Conclusion: Haemophilus influenzae infections mainly occur in children under 6 years old, with seasonal peaks in spring and winter. The COVID-19 pandemic influenced infection patterns of specific age groups and resistance trends. Caution is required for commonly resistant antibiotics, and continuous resistance monitoring is necessary.

Keywords: haemophilus influenzae, children, antibiotics, antimicrobial resistance, COVID-19