Microbiology and epidemiology of enteroaggregative Escherichia coli isolated from UK residents in England, 2016–2023: what are the risks to public health?

<b>Introduction.</b> Following two large foodborne outbreaks of the gastrointestinal pathogen, enteroaggregative <i>Escherichia coli</i> (EAEC), in Germany in 2011 and the UK in 2014, the UK Health Security Agency (UKHSA) implemented enhanced surveillance strategies for EAEC.<b>Gap Statement.</b> The surveillance of diarrhoeagenic <i>E. coli</i> in England focuses on Shiga toxin-producing <i>E. coli</i> (STEC), and the true clinical and community burden of EAEC is unknown. This gap extends globally, as many countries lack the infrastructure, diagnostic tools and healthcare facilities to resource surveillance programmes for EAEC.<b>Aim.</b> The aim of the study was to review the microbiological typing data and demographic data linked to isolates and cases diagnosed from 2016 to 2023 and to assess the risk to public health.<b>Methodology.</b> Faecal samples that tested positive by PCR for diarrhoeagenic <i>E. coli</i> at local microbiology diagnostic laboratories were referred to the UKHSA for confirmation and culture. Isolates identified as EAEC were sequenced on the Illumina HiSeq and NextSeq platforms. Sequence type, serotype and antimicrobial resistance (AMR) profile were derived from the genome sequence. Age, sex and travel histories were linked to the typing data.<b>Results.</b> There was a total of 1,402 notifications of EAEC, exhibiting a fivefold increase in diagnoses from 93 in 2016 to 524 in 2023. The most common sequence types (STs) were ST34 (<i>n</i>=202/1,402, 14.4%), ST10 (<i>n</i>=185/1,402, 13.2%), ST200 (<i>n</i>=183/1,402, 13.1%) and ST678 (<i>n</i>=101/1,402, 7.2%), and the most common serotypes were O92:H33 (<i>n</i>=130/1,402, 9.3%), O175:H31 (<i>n</i>=78/1,402, 5.6%) and O99:H10 (<i>n</i>=78/1,402, 5.6%). Most cases were female (<i>n</i>=748/1,372, 54.5%) and/or were aged <10 (<i>n</i>=387/1,372, 28.2%), within which 299 out of 387 (77.3%) were <5 years old. Of the 756 out of 1,386 (54%) cases that had a travel history, 597 out of 756 (79%) reported foreign travel within 7 days of onset of symptoms. AMR was detected in 1,030 out of 1,402 (73.5%) isolates with resistance to fluoroquinolone (<i>n</i>=810/1,402, 57.8%) and beta-lactam (<i>n</i>=807/1,402, 57.6%) antibiotics being the most common.<b>Conclusion.</b> Given the burden of disease caused by EAEC in the community, the high proportion of infections in children and travellers, the risk of the emergence of hybrid STEC/EAEC pathotypes and the high proportion of AMR, we recommend that EAEC should be part of the diagnostic algorithm in the UK.