Distribution, carbapenem resistance and DTR dynamics of ESKAPEEc pathogens from pediatric bloodstream infections in Sichuan Province, 2017-2025: epidemiological characteristics under COVID-19 pandemic and emerging linezolid MIC creep.

OBJECTIVE

To characterize the distribution and antimicrobial resistance evolution of ESKAPEEc pathogens causing pediatric bloodstream infections in Sichuan Province across the COVID-19 era, and to systematically evaluate the epidemiology of carbapenem resistance (CR), difficult-to-treat resistance (DTR), and MIC drift in vancomycin and linezolid, thereby addressing a long-standing gap in longitudinal pediatric multidrug-resistant surveillance in Southwest China.

METHODS

A multicenter retrospective study was conducted using pediatric blood culture data from 134 healthcare institutions in Sichuan Province between 2017 and 2025. A total of 20,018 isolates were included and stratified into pre-pandemic, pandemic, and post-pandemic periods. Antimicrobial susceptibility testing and DTR classification were interpreted according to CLSI M100 (35th edition) criteria. Statistical analyses were performed using WHONET 5.6 and SPSS 26.0.

RESULTS

A total of 5,236 ESKAPEEc isolates were identified, accounting for 26.2% of all bloodstream isolates. Detection rates increased during the pandemic period and declined thereafter. Carbapenem resistance rates in Escherichia coli and Klebsiella pneumoniae were significantly higher in the post-pandemic period compared with the pre-pandemic baseline. The overall DTR prevalence was 8.6%, with Acinetobacter baumannii exhibiting the highest DTR burden (87.3%) despite a declining temporal trend, whereas DTR in K. pneumoniae increased progressively over time. Reliance on CR criteria alone failed to identify a substantial proportion of DTR-positive E. coli isolates. All Staphylococcus aureus isolates remained susceptible to vancomycin and linezolid in vitro, with stable vancomycin MIC distributions; however, a high-MIC subpopulation among linezolid-treated MRSA isolates increased significantly over time (r=0.767, P = 0.016). Distinct age-stratified differences were observed in both pathogen distribution and resistance profiles.

CONCLUSIONS

The COVID-19 pandemic exerted a bidirectional and sustained impact on the pediatric ESKAPEEc landscape and resistance ecology in Sichuan Province. Post-pandemic escalation of carbapenem resistance persists. The persistently high DTR burden in A. baumannii and early MIC drift toward linezolid in MRSA represent two critical regional threats in pediatric infectious disease management. Regional surveillance systems should incorporate DTR metrics alongside CR monitoring and implement age-stratified, precision-based antimicrobial stewardship strategies.