sequences of bacteria
Background: During the COVID-19 pandemic, non-pharmaceutical                 interventions (NPIs) suppressed the transmission of respiratory pathogens. Following                 the relaxation of NPIs, the epidemiological characteristics of respiratory pathogens                 has shifted substantially. Chinese surveillance data reveal a rising isolation rate                 of Haemophilus influenzae, necessitating a clearer understanding of the pandemic's                 impact on the prevalence and antibiotic resistance of this pathogen. Aim: To                 investigate changes in the prevalence and antibiotic resistance of H. influenzae                 clinical isolates in Nanjing, China, before, during, and after the COVID-19                 pandemic. Methods: We retrospectively analyzed epidemiological and antibiotic                 resistance data from 805 clinical H. influenzae isolates, collected in Nanjing,                 spanning pre-pandemic (20172019), pandemic (20202022), and post-pandemic (20232024)                 periods. Whole-genome sequencing (WGS) was performed on 46 randomly selected                 isolates (stratified by period: n = 14, 12, 20) to determine serotypes, sequence                 types (STs), resistance determinants, and virulence factors. Results: After the                 COVID-19 pandemic, the isolation rate of H. influenzae increased, with a demographic                 shift toward elderly patients. Susceptibility to ampicillin, cefuroxime, and                 azithromycin progressively declined, while remaining high to meropenem and                 levofloxacin. The proportion of -lactamase-positive isolates rose compared to the                 pre-pandemic period. Genomic analysis confirmed that all sequenced isolates were                 nontypeable H. influenzae (NTHi) and identified 26 distinct STs, with the ST-107                 complex being dominant. Key antibiotic resistance genes, such as mutated ftsI and                 blaTEM-20, as well as multiple virulence genes, were detected. Conclusion: The                 post-pandemic period is marked by increased prevalence and heightened antibiotic                 resistance in H. influenzae. Continuous monitoring of resistance and virulence is                 essential to inform effective control strategies.
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hin20