Summary

The Enteric Reference Laboratory (ERL) typed a total of 712 Yersinia isolates in 2024 including 12 Y. pseudotuberculosis with the remainder typed as Y. enterocolitica (700/712, 98.3%). The most common type for Y. enterocolitica was biotype 2/3 serotype O:9 (also reported as its genomic equivalent, sequence type 12) for a total of 429 out of 700 (61.3%) similar to previous years with 68.0% in 2023, 71.1% in 2022 and 62.7% in 2021. Biotype 1A (comprised of many sequence types and denoted by the presence of the ystB toxin gene), along with biotype 4 serotype O:3 (also reported as sequence type 18) were the next most common types of Y. enterocolitica identified with 206 and 54, respectively (29.4% and 7.7%). This was the highest relative abundance of biotype 1A in recent years with 20.6% in 2023, 17.1% in 2022 and 17.3% in 2021. There was also an increase in Y. pseudotuberculosis isolates relative to recent years with only five in 2023, nine in 2022 and 10 in 2021. It should be noted that Y. pseudotuberculosis is not included in standard enteric panels at all the diagnostic testing labs and may be underreported.