Extraintestinal pathogenic Escherichia coli (ExPEC) O-serotype distribution and antibiotic resistance profiles among the aging population in China: A longitudinal, multi-center study.

Extraintestinal pathogenic Escherichia coli (ExPEC) is a leading cause of community-acquired bacteremia and sepsis, which contributes to the substantial burden of invasive E. coli disease (IED) in older adults. This study aimed to estimate the O-serotype distribution of blood and sterile site ExPEC among older adults in China and the characteristics of antimicrobial resistance, O-serotypes, and O genotypes. A total of 499 non-duplicated clinical isolates of E. coli derived from sterile body fluids from subjects aged ≥ 60 years from 55 medical institutions participating in the CHINET from different regions of China from 2016 to 2022 were collected. Antimicrobial susceptibility testing and whole genome sequencing (WGS) were performed for all isolates. For isolates with an O genotype pertaining to ExPEC9V (a group of 9 O-serotypes with high prevalence among bloodstream infections globally), an agglutination assay was conducted for validation. In this study, 82.2% and 10.7% of ExPEC isolates were tested as multidrug-resistant (MDR) and carbapenem-resistant E. coli (CREC), respectively. WGS revealed diverse STs and phylogroups. The most prevalent O serotypes were O25 (14.2%), O75(6.2%), O1(5.6%), O6(4.6%), O15(3.8%), O45(3.6%), O101(3.4%), O11(3.4%), O153(3.4%), O8(3.4%), O2/O50(3.0%), and O9/O9a(3.0%). Among MDR isolates, O25 was the dominant O serotype. 40.1% of isolates were identified as ExPEC9V. In conclusion, O25 is the most prevalent O serotype among ExPEC isolates. The ExPEC9V O-serotype prevalence is generally consistent across MDR and different sexes.