The CDC has ascertained epidemiology, identified the serotype, and determined extent of antimicrobial resistance of extraintestinal invasive Escherichia coli (E coli), the most common pathogen in community-onset sepsis, in a surveillance study intended to inform prevention strategies and improve sepsis detection.1
Characterizing antimicrobial resistance was an important element of the study, as recent data from hospitalized patients in the US indicate that more than 34% of invasive E coli infections are resistant to 3 or more antibiotic classes.In addition, the genetic elements conferring antimicrobial resistance in E. coli can transfer to other pathogenic or opportunistic bacteria.
"Despite its clinical importance, no routine public health surveillance has previously existed in the US for invasive E coli of any antimicrobial susceptibility phenotype," observe study lead author Heather Grome, MD, MPH, Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention (CDC), Atlanta, GA, and colleagues
This laboratory- and population-based surveillance study was conducted under the auspices of the CDC's Emerging Infections Program (EIP) and the Multi-site Gram-negative Surveillance Initiative (MuGSI).The surveillance population was drawn from selected metropolitan counties at 9 EIP sites (comprising total population of more than 7.2 million) in California, Colorado, Georgia, Maryland, Minnesota, New Mexico, New York, Oregon, and Tennessee. Data were obtained for the period of June to August 2023.
What You Need to Know
The CDC surveillance identified an estimated annual incidence of nearly 75 cases per 100,000 people, with more than 95% of patients hospitalized and almost 8% dying—disproportionately affecting older adults and women, and most often originating from urinary tract infections.
Nearly 14% of invasive infections involved ESBL-producing strains, and resistance to commonly used antibiotics such as ciprofloxacin and trimethoprim-sulfamethoxazole was widespread, raising concerns for frontline clinicians managing sepsis and urosepsis.
The dominance of specific O-antigen serotypes (O25B, O2, and O6) supports ongoing vaccine development efforts, which could reduce invasive disease burden and antibiotic use, forming a key component of long-term antimicrobial resistance mitigation strategies.
An incident case, defined as the first isolation of E coli of any antimicrobial susceptibility from a normally sterile body site, was identified through query of clinical laboratory automated testing. Candidate cases then underwent medical record review to ascertain elements such as patient demographics, underlying conditions, health care exposures and outcomes, associated infection types and antimicrobial susceptibility testing results.
The investigators identified 1,345 cases of invasive E coli infection in 1,334 unique case-patients; with 1,223 (90.9%) from blood and 122 (9.1%) from other sterile sites. Most infections were initially associated with the urinary tract.The cases corresponded to an estimated annual incidence of 74.7 (51.4-96.0) per 100,000 population, with higher incidence rates in females and in adults 60 years of age or older. 1,279 of the patient cases (95.1%) required hospitalization, and 106 (7.9%) died.
Extended-spectrum ß-lactamase-producing (ESBL) E coli were found in 185 (13.8%) of the infections.275 of 1061 isolates (25.9%) were determined to be resistant to ciporofloxacin, and 370 of 1285 (28.8%) resistant to trimethoprim-sulfamethoxazole.
The investigators characterize the approximate 14% of cases associated with an ESBL isolate as "alarming."
"The rise in ESBL E coli may give pause to clinicians making empiric treatment decisions for syndromes frequently caused by E coli, such as urospepsis," Grome and colleagues suggest.
The most prevalent serotypes were O25B (137 isolates [16.2%]), O2 (93 isolates [11.0%]), and O6 (84 isolates [9.9%]). The investigators note that the high prevalence of the O antigen serotype has been found by others, and serves as a basis for clinical trials of several different polysaccharide conjugate vaccine candidates targeting O antigens.
"Vaccines targeting invasive E coli could play an important role in a broader strategy to reduce antimicrobial resistance by preventing infections and reducing reliance on antibiotic treatment," Grome and colleagues posit.
Reference
1. Grome HN, Brandenburg JM, Kent AG, et al. Extraintestinal invasive Escherichia coli infections in the US. JAMA Netw Open. 2026; 9(2):e2557201. doi:10.110/jamanetworkopen.2025.57201.
