Yersinia enterocolitica is a well known food-borne bacterium which belongs to the Enterobacteriaceae family. Y. enterocolitica is pathogenic for humans and it causes a wide spectrum of diseases ranging from self-limiting gastrointestinal diseases to fatal sepsis depending on the age and the immunity of the infected person. Oral ingestion of undercooked raw meat products, unpasteurised milk and contaminated water are the main sources of acquisition of this bacterium. Y. enterocolitica strains are categorized into six biotypes (1A, 1B, 2, 3, 4 &5). These six biotypes are further classified into high pathogenic, low pathogenic and non-pathogenic biotypes depending on their pathogenicity in the mouse infection model. This project compared the pathogenic potential of Yersinia enterocolitica high pathogenic, low pathogenic and non-pathogenic biotypes. The HEp-2 laryngitic human epithelial cell line and the alternative infection model Galleria mellonella greater wax moth larvae are the main infection models used to investigate the pathogenic potential of Y. enterocolitica biotypes. A diverse collection of Y. enterocolitica strains was used by which this strains collection is encompassing all six biotypes and all major serotypes. These strains were isolated from human and animal origins. Here novel results are presented showing new infection phenotypes of the Y. enterocolitica strains. All Y. enterocolitica biotypes strains were invasive to the HEp-2 epithelial cell line and pathogenic to the Galleria insect model. The non-pathogenic biotype was the most lethal in the Galleria model while the high pathogenic biotype shows little to no pathogenicity. The low pathogenic biotypes were moderately pathogenic to the Galleria insect model. The pYV plasmid showed a minor role in modulating the virulence in the Y. enterocolitica pathogenic biotypes. Investigating the in vivo Y. enterocolitica-Galleria interaction showed that Y. enterocolitica pathogenic biotypes bacterial cells were growing inside the Galleria larvae while the non-pathogenic biotype bacterial cells were dying. The heat-killed Y. enterocolitica strains were completely avirulent to the Galleria larvae.