Epidemiology of Shiga toxin-producing Escherichia coli other than serotype O157:H7 in England, 2016-2023

Introduction. Shiga toxin-producing Escherichia coli (STEC) infections are of public health concern as STEC can cause large national foodborne outbreaks of severe gastrointestinal disease, particularly in the young and elderly. In recent years, the implementation of PCR by diagnostic microbiology laboratories has improved the detection of STEC, and there has been an increase in notifications of cases of non-O157 STEC. However, the extent this increase in caseload can be attributed to the improved detection by PCR, or a true increase in non-O157 STEC infections, is unknown.Gap Statement. Epidemiological and microbiological data and analyses describing the trends in non-O157 STEC in England since the implementation of PCR are limited.Aim. Demographic, microbiological and clinical characteristics of non-O157 STEC from 8 years (2016-2023) of laboratory surveillance data were analysed to understand the recent trends in non-O157 serotypes and the incidence of disease in England.Methodology. All human isolates of STEC non-O157 detected between 2016 and 2023 were extracted from the laboratory surveillance system. Microbiological data were analysed and linked to clinical outcomes.Results. There was an almost 10-fold increase in diagnoses of non-O157 STEC from 2016 (n=297) to 2023 (n=2341). A total of 9378 isolates of non-O157 STEC were detected, comprising 338 different serotypes, and were linked to 9311 individuals. A higher proportion of non-O157 STEC cases were female (56%) and aged between 20 and 39 years (27%). The most common non-O157 serotypes were O26:H11 (16%), O146:H21 (12%), O91:H14 (11%), O128:H2 (6%), O145:H28 (5%) and O103:H2 (4%). STEC O26:H11 was more frequently reported in under 5s than any other age group (38%), whereas the other common serotypes were more frequently isolated from adults. Stx2a, which has been associated with greater disease severity, was detected in 18% of cases. Where clinical details were available, 27% of non-O157 cases were admitted to the hospital and 6% developed HUS. Cases of STEC O145:H28 reported a higher rate of hospitalisation than other non-O157 STEC cases. The serotypes most likely to be associated with progression to HUS were O26:H11 (9%) and O145:H28 (7%). STEC harbouring stx2f (19%), stx2a (11%) and stx2d (11%) were most frequently isolated from cases with HUS.Conclusion. The implementation of widespread PCR testing in England has facilitated better surveillance of STEC non-O157, with respect to establishing the true incidence and burden of disease of non-O157 STEC and monitoring the emergence of highly virulent strains.