Surveillance of genomic diversity and antimicrobial resistance in enterotoxigenic Escherichia coli in England, 2015–2023

<b>Introduction.</b> Enterotoxigenic <i>Escherichia coli</i> (ETEC) are one of the leading causes of gastrointestinal infections globally, primarily affecting children in low- and middle-income countries and travellers to endemic regions.<b>Gap Statement.</b> The surveillance of diarrhoeagenic <i>E. coli</i> in England focuses on Shiga toxin-producing <i>E. coli</i>, and the true clinical and public health burden of ETEC is unknown. This gap extends globally, as many countries, particularly those in endemic regions, lack the infrastructure, diagnostic tools and healthcare facilities to resource surveillance programmes for ETEC.<b>Aim.</b> The aim of this study was to utilize available data to describe the epidemiology, genomic diversity and antimicrobial resistance (AMR) of ETEC in England.<b>Methodology.</b> A total of 587 isolates of ETEC cultured from faecal specimens referred to the Gastrointestinal Bacteria Reference Unit at the UK Health Security Agency for further testing, from 2015 to 2023, were sequenced to determine sequence type (ST), serotype, virulence and AMR profiles, and integrated with epidemiological data obtained from referral forms.<b>Results.</b> Overall, the number of ETEC notifications increased annually, with a 35.5-fold increase from 2015 to 2023. There were more female cases (51.7%) than males (48.3%), with the highest proportion of cases belonging to the 50-59 age group (18.6%). Nearly half of the cases (49.5%) were travel-associated, with Egypt, Pakistan, India, Turkey and Mexico being the top travel destinations. At least 139 STs and 132 serotypes were identified, with the most common ST-serotype profiles being ST4 O6:H16 (<i>n</i>=74) and ST182 O169:H41 (<i>n</i>=66). Genome-derived AMR data revealed widespread resistance to fluoroquinolones and <i>β</i>-lactams, including third-generation cephalosporins, and over 40% of isolates (<i>n</i>=239/587) were resistant to three or more classes of antimicrobials.<b>Conclusion.</b> We observed an increase in notifications of multidrug-resistant ETEC over the last decade, mainly associated with travellers' diarrhoea. Nationwide expansion of PCR-based diagnostics for ETEC, alongside strengthening collaboration with public health agencies and genomic data sharing at a local, national and international level, is critical for strengthening surveillance and accurately assessing the true burden of ETEC locally and on a global scale.