Distribution and Antibiotic Resistance of Pathogens in Bloodstream Infections Among Elderly Patients in Sichuan Province (2020–2024)

Zhuorui You,1 Xiangning Huang,2 Xin Liu,2 Hua Yu,2 Shanshan Long2 1School of Medicine, University of Electronic Science and Technology of China, Chengdu, 611731, People’s Republic of China; 2Department of Laboratory Medicine, Sichuan Provincial People’s Hospital, University of Electronic Science and Technology of China, Chengdu, 610072, People’s Republic of ChinaCorrespondence: Shanshan Long, Email [email protected] Hua Yu, Email [email protected]: To characterize the distribution and antimicrobial resistance patterns of pathogens causing bloodstream infections in elderly patients in Sichuan Province from 2020 to 2024.Methods: Non-duplicate isolates from blood of patients aged ≥ 65 years in 134 provincial medical institutions (113 tertiary, 21 secondary) were collected and tested per a unified protocol. Species identification and susceptibility were interpreted using CLSI M100 criteria. Data were analyzed with WHONET 5.6. The study period was stratified into pandemic (2020– 2022) and post-pandemic (2023– 2024) phases to assess effects on multidrug-resistant and pandrug-resistant organisms.Results: 65,603 isolates were obtained from elderly patients’ blood specimens, of which 23,350 (35.6%) were Gram-positive and 42,253 (64.4%) were Gram-negative. The five most frequently detected organisms were Escherichia coli (38.4%), Klebsiella pneumoniae (12.6%), Staphylococcus hominis (6.6%), Staphylococcus epidermidis (6.0%), and Staphylococcus aureus (5.8%). E. coli exhibited low carbapenem resistance (ertapenem 0.8%, imipenem 0.9%, meropenem 0.9%), whereas K. pneumoniae showed carbapenem resistance of 6.7– 8.4%. Methicillin-resistant S. aureus and methicillin-resistant coagulase-negative staphylococci were detected at rates of 29.1% and 70.8%, respectively; no vancomycin-resistant staphylococci were identified. A total of 126 pandrug-resistant Acinetobacter baumannii (PDR-AB) isolates were identified, accounting for 11.2% (126/1124). No pandrug-resistant Enterobacterales or Pseudomonas aeruginosa were detected. In the post-pandemic period, the detection rates of carbapenem-resistant A. baumannii and carbapenem-resistant Klebsiella pneumoniae increased significantly compared with the pandemic period (P < 0.05).Conclusion: From 2020 to 2024, a diverse spectrum of bacterial species was isolated from bloodstream infections in elderly patients in Sichuan Province. Following the COVID-19 pandemic, the burden of carbapenem-resistant organisms increased. Region-specific antimicrobial resistance surveillance and strengthened in-hospital infection control are essential to guide appropriate antibiotic use and to curb the spread of resistant organisms.Keywords: elderly patients, bloodstream infections, multidrug-resistant organisms, Sichuan Province, COVID-19 pandemic