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2023 - Yersinia isolates

Please note: As of 1 July 2025, the New Zealand Institute for Public Health and Forensic Science (PHF Science) is the new name for the Institute of Environmental Science and Research (ESR). Research and reports published prior to this date may reference the organisation’s former name.

Summary

The Enteric Reference Laboratory (ERL) typed a total of 974 Yersinia isolates in 2023 including 5 Y. pseudotuberculosis with the remainder typed as Y. enterocolitica. The most common type for Y. enterocolitica was biotype 2/3 serotype O:9 with 659/969 (68.0%) isolates confirmed. This is similar to previous years where this serotype accounted for 71.1% in 2022, 62.7% in 2021, and 55.9% in 2020 with evidence of a possible plateau following a yearly increase. Biotype 1A and biotype 4 serotype O:3 with 200 and 89 isolates out of the 659 total Y. enterocolitica identified, respectively (20.6% and 9.2%). Biotype 1A had a similar trend to the biotype 2/3 serotype O:9 with 17.1% of Y. enterocolitica isolates typed in 2022, 17.34% in 2021, and 23.9% in 2020. This coincides with a downward trend in identifications of Y. pseudotuberculosis with 13 in 2020, 10 in 2021, and 9 in 2022. It is unclear how this relates to culture independent testing with some manufacturer’s panels able to detect Y. pseudotuberculosis and enterocolitica while others only detect enterocolitica.

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