What question did this study set out to answer?

This research aims to characterize the molecular epidemiology of ExPEC and assess its antibiotic resistance profiles.

January 14, 2026Open Forum Infectious Diseases0 citationsOpen Access

P-1158. Molecular Characterization of Extraintestinal Pathogenic Escherichia coli (ExPEC) from the Emerging Infections Program (EIP)─United States, 2023

AKAlyssa G. KentCenters for Disease Control and Prevention HGHeather N. GromeCenters for Disease Control and Prevention JBJoshua BrandenburgOak Ridge Associated Universities

Key Points

This research aims to characterize the molecular epidemiology of ExPEC and assess its antibiotic resistance profiles.
Conducted active laboratory- and population-based surveillance for invasive and urinary ExPEC in nine and three US sites, respectively.
Isolates underwent whole-genome sequencing and multi-locus sequence typing for analysis.
Defined cases based on the first isolation of E. coli from sterile sites or urine within 30 days.
Collected 846 invasive ExPEC and 939 urinary ExPEC isolates during surveillance.
Identified a 19.0% prevalence of ST131 in invasive cases and 15.4% in urinary cases.
Detected O25b as the dominant serotype for both invasive and urinary ExPEC, with at least 16.2% and 12.2% respectively.
All isolates contained at least one beta-lactamase gene, indicating significant antibiotic resistance.

Abstract

Abstract Background Extraintestinal pathogenic E. coli (ExPEC) is a major contributor to healthcare-associated infections (HAIs) and a leading cause of urinary tract infections (UTIs) and sepsis in the United States. Despite its substantial burden, comprehensive molecular epidemiological data on ExPEC in the United States remain limited. Methods In 2023, the Emerging Infections Program piloted active laboratory- and population-based surveillance for invasive ExPEC (iEC) across nine U.S. sites (CA, CO, GA, MD, MN, NM, NY, OR, TN) from June to August and for urinary ExPEC (uEC) at three sites (CA, GA, NY) in August. Cases were defined as the first isolation of E. coli from a sterile site (iEC) or urine (uEC) from a surveillance-area resident in a 30-day period. All iEC and a random sample of uEC isolates were sent to the CDC for molecular subtyping via whole-genome sequencing (WGS) analysis including multi-locus sequence typing, in silico serotyping, and antibiotic resistance gene profiling. Results The collection included 846 iEC and 939 uEC isolates. The sequence type (ST) 131 pandemic clone was the most prevalent lineage, comprising 19.0% and 15.4% of iEC and uEC isolates, respectively. In silico serotyping identified O25b as the dominant serotype, representing 16.2% and 12.2% of iEC and uEC isolates, respectively. All isolates harbored at least one beta-lactamase gene, three isolates harbored a carbapenemase gene (KPC-3 and OXA-244), and 11% harbored at least one extended-spectrum beta-lactamase gene. Additionally, approximately one-third of isolates harbored genetic determinants associated with multidrug resistance (defined as resistance to ≥3 antimicrobial classes). Conclusion These findings enhance our understanding of ExPEC molecular epidemiology, highlighting the dominance of ST131 and O25b, along with widespread beta-lactamase and multidrug resistance. These baseline data are crucial considerations for vaccine development and antimicrobial stewardship to mitigate ExPEC’s public health impact. Disclosures All Authors: No reported disclosures

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