Especially,

the poultry-associated BAPS cluster 1 was very heterogeneous; Fulvestrant in vitro the ST-45 CC was most common and grouped together with several uncommon, unrelated clonal complexes, often not found in our poultry isolates. In our previous study [25], the ST-45 CC found in our human isolates was associated with tasting of raw or undercooked meat as well as contact with dogs or cats. Also, the ST-45 CC has been found from penguins on the Antarctic [37], implying that this CC has a wide host range and is environmentally well adapted. The ST-22, ST-42 and ST-48 CCs, which were grouped together with the ST-45 CC in BAPS cluster 1, have been commonly found in companion animals in other studies [11, 28, 38]. However, more studies are needed to establish the role of environmental contamination sources serving as C. jejuni vectors for both human infection and chicken colonization. Most admixture was found in clusters 1 and 4 with the majority of admixed STs being novel and associated with

the bovine isolates. All admixed STs with the highest posterior probability in cluster 1 (poultry-associated) were admixed with cluster 4 (bovine-associated) and most of these STs were found only in bovine isolates. In contrast, most admixed STs with the highest posterior probability in cluster 4 were admixed with clusters 2 and 3, in which only human isolates were assigned to NVP-LDE225 solubility dmso and mostly contained uncommon, unassigned STs. These findings could imply that recombination is more common in STs specific to bovines, which is supported by the high diversity of our bovine isolates. Bovines have a longer life-span than poultry and persistence of C. jejuni clones in herds and specific bovine-associated lineages imply that these strains can adapt to long-lasting colonization, thereby increasing the chance of horizontal transfer of genetic material and recombination. The ST-61 CC was found as a separate cluster (cluster 5) by BAPS, with C-X-C chemokine receptor type 7 (CXCR-7) the exception of ST-618 (cluster 4, admixed with cluster

1). This finding was not surprising since the ST-61 CC is known to have imported C. coli alleles (e.g. uncA17) and therefore is phylogenetically less related to other C. jejuni clonal complexes [39]. Both ST-618 and ST-3509 do not possess the uncA17 allele, but ST-3509 carries the uncA38 allele. This allele is common in both the ST-61 CC and the C. coli related ST-828 CC and likely the presence of this allele caused ST-3509 to be included in BAPS cluster 5. ST-618, however, carries the uncA5 allele, which is commonly found in both the ST-21 CC (cluster 4) and the ST-48 CC. This explains why this particular ST was grouped together with the ST-21 CC and at the same time admixed with cluster 1. These results demonstrate that the import of C. coli DNA can have a large impact on the MLST analysis of C. jejuni strains and this should be taken into account in source attribution studies.