2022 - STEC isolates

Summary

The Enteric Reference Laboratory (ERL) typed 781 STEC isolates out of 1022 cases notified. This was an increase of 79 additional isolates, compared with 2021. The most commonly identified serotypes out of the total of 781 were O157:H7 (266, 34.1%) and O26:H11 (109, 14.0%) followed by O128:H2 (83, 10.6%), O146:H21 (44, 5.6%), and O38:H26 (39, 5.0%). Amongst typed STEC isolates, the percentage of O157:H7 increased from 27.5% in 2021, while the percentage of O26H11 decreased from 18.66% in 2021. Where subtyping of the stx gene was successful, 207/265 (78.1%) O157:H7 and 54/97 (55.7%) O26:H11 isolates were stx2a positive. The stx2a subtype has been strongly associated with haemolytic uremic syndrome (HUS) in New Zealand. Haemolytic uraemic syndrome (HUS) was confirmed in 19 hospitalised STEC cases. Among these cases, a serotype was determined in 17 cases (89.5%). Of these, nine were due to E. coli O157:H7 and seven were due to E. coli O26:H11. All typed isolates from STEC cases with HUS were positive for stx2a.

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