Our findings indicate that about half of the typical and atypical EPEC strains and Talazoparib price serotypes are closely related to EHEC regarding these virulence attributes (Table 2). The presence of OI-122 encoded genes, followed by OI-71 were most significant for the assignment of EPEC to the “”EHEC-related”" Cluster 1 confirming data from our previous study performed on a different collection of strains [17]. The OI-57 encoded

genes nleG5-2 and nleG6-2, as well as the espK gene were not as strongly associated with Cluster 1, as the OI-122 and OI-71 genes. Recently, the OI-57 associated genes adfO and ckf were reported to be present in 30 (71%) of 42 investigated EPEC strains Lonafarnib research buy but a high variability of OI-57 associated orfs in EPEC strains was observed [28]. This could explain the results of our study, where the OI-57 associated nleG5-2 gene was found infrequently in all EPEC, whereas the nleG6-2 gene was frequent in atypical EPEC (45.5%) but rarely found in typical EPEC (12.3%) (Table 1). Further work is needed to define the genes of OI-57 that are most suitable for the molecular risk assessment of EHEC and EPEC strains. In our study, EHEC-plasmids were associated with EHEC, STEC and Sapitinib cell line atypical EPEC, but not with typical EPEC strains. EHEC-plasmids are frequently harboured by classical EHEC

but also by many LEE-negative aminophylline STEC strains [32–34]. Correspondingly, EHEC-plasmid encoded genes ehxA, etpD, katP and espP had only a small influence on Cluster 1 formation, confirming results of previous studies [16, 17]. In this study, EHEC-plasmid genes were significantly more associated with atypical EPEC Cluster 1 than with Cluster 2 strains. The high proportion of EHEC-plasmid

positives among Cluster 1 strains suggests that many of these may have derived from EHEC by losing stx-genes. A loss of stx-genes was reported to occur frequently in classical EHEC strains [23, 26]. EHEC-plasmid genes were found in 23/29 (79.3%) of atypical EPEC Cluster 1 strains belonging to EHEC related serotypes O26:H11, O103:H2, O145:H28 and O157:H7 (data not shown). These 30 EHEC-like strains showed the same virulence characteristics (presence of OI-122 genes) as their homologous EHEC strains. In addition to this, there are epidemiological findings pointing to a closer relationship between “”Cluster 1″” atypical EPEC and EHEC strains. Significantly (p < 0.05) more typable (78/120 = 65.0%) Cluster 1 strains than Cluster 2 strains belonged to serotypes (18/40 = 45.0%) that are associated with the production of Shiga toxins (38). Only 26.6% (24/90) of the atypical EPEC strains of Cluster 2 showed O:H types (10/46 = 21.7) previously associated with Stx-production. Typical EPEC were also found to split into Cluster 1 and Cluster 2 strains.