Summary

The Enteric Reference Laboratory (ERL) typed 741 STEC in 2025, an increase of 18 from the previous year (723 in 2024). The most common serotypes of the 741 total isolates identified were O157:H7 (160, 21.6% sequence types 11, 10084 and 17481) and O26:H11 (148, 20.5% sequence types 21 and 17629) followed by O128:H2 (86, 11.6% sequence types 25, 811, 4748, 8381, 11349, 17736, 17812, and 18274), O38:H26 (36, 4.8% sequence types 10 and 4761) and O146:H21 (35, 4.7% sequence types 442, 829, 1043, 1744, 1758, 1802, and 1866). Serotype O91:H14 was the fourth most common in 2024 with 49 isolates (6.8%) but in 2025 there were 28 isolates. O157:H7 and O26:H11 remained the most common serotypes identified with a slight increase in O26:H11 from 19.4% in 2024 to 20.5% in 2025. Where subtyping of the stx gene was successful, 113/160 (70.6%) O157:H7 and 89/148 (60.1%) O26:H11 isolates were stx2a positive. This is an increase from 69.0% of O157:H7 and 50.7% of O26:H11 isolates in 2024. For all cases reported to EpiSurv as progressing to haemolytic uremic syndrome (HUS) with a typed isolate, 26/26 (100%) were stx2a, an increase from 2024 where 88.2% were stx2a. Also, 17 of the cases were O26:H11 (65.4%) and nine were O157:H7 (34.6%), all of which were eae positive. In total there were 93 stx2a positive isolates with the vast majority represented by O157:H7 and O26:H11 (113 and 89 respectively).