A case-control study and molecular epidemiology of yersiniosis in Aotearoa New Zealand.

The objective of this study was to determine risk factors and sources attributed to yersiniosis in Aotearoa New Zealand (NZ). A risk factor questionnaire was administered to 247 notified yersiniosis cases and 258 control participants from the Canterbury and/or Wellington regions of NZ. Yersinia sp. isolates from clinical cases and a range of food sources were whole-genome sequenced and genetically compared. Yersinia enterocolitica (YE) bioserotype 2/3, O:9 [McNally multi-locus sequence type (ST) 12] and YE Biotype (BT) 1A (46 different STs) predominated within the consented cases (45 and 27%, respectively). Exposure to pork was identified as a significant risk factor for cases associated with YE ST12. The presence of YE ST12 was confirmed in retail raw meat, primarily raw pork. Single-nucleotide polymorphism (SNP) analysis identified multiple genomically very closely related clusters (0-5 SNPs) of YE ST12, predominately from raw pork with clinical cases from one or both regions. Risk factors associated with YE BT 1A included the consumption of cooked seafood, sushi, tofu, and some vegetable types. Analysis of specific risk factors and SNP analysis, combined, indicate that raw pork is a significant risk factor for exposure and infection to pathogenic YE cases, but not BT 1A cases.