All PCR products were run on a BioAnalyzer, using the Agilent DNA 1000 Kit (Agilent Technologies) as described by the manufacturer to check for positive amplification. All 17 SF O157 isolates were positive for rfbO157, fliCH7, SRL and dinB, as well as stx2 and eae. Stx2EDL933 was the only stx2 subtype detected. Additionally, the strains harboured nleB and stcE. Fifteen of 17 isolates (88%) were positive for the ehxA gene, and 14/17 strains (82%) selleck inhibitor carried cdt (Table 1). terE, stcEO103, saa and subA were not present in any of the strains examined (Table 1). The SF O157 isolates recovered from Norwegian patients

before 2009 showed distinct MLVA profiles, indicating that the cases concerned did not belong

to common-source outbreaks. However, all isolates obtained from 2009 through May 2011 grouped into one MLVA genotype (Table 1). Screening with the stx8 primer set showed that only two SF O157 were positive for these primers, whereas 15 were negative (Table 1). All isolates failed to amplify the q933 and q21 genes. PCR and sequencing of the stx2 promoter region with the primers slt2s-2 and 595 showed that 15 of the SF O157 (all stx8 negative) were identical and differed from the NSF O157 strain EDL933 sequence (AE005174) by five nucleotides (Fig 1). The sequence differences were seen between the tRNA genes argN and argO located proximately to the Proteasome inhibitor stx2 promoter region, and in the argO gene, between the −35 and the

−10 region within the stx2 promoter. However, these isolates showed identical sequence to the O111:H− strain 11128 (AP010960) in this region (Fig 1). The two last SF O157 (both stx8 positive) differed from the EDL933 sequence (AE005174) in one nucleotide only, located in the tRNA gene argN (Fig 1). We Tolmetin determined the nucleotide sequences of the q gene, the region between the q gene and the stx2 gene, the stx2 gene and the 500-bp region downstream of the stx2 gene in the SF O157 strains 1106-4002 (EMBL/GenBank accession number FR874039), 1109-0113 (outbreak strain from 2009, EMBL/GenBank accession number FR874040) and 1108-2781 (EMBL/GenBank accession number FR874041). Strains 1106-4002 and 1109-0113 showed identical sequences in reversed complement to the E. coli O111:H− strain 11128 (AP010960) in all the examined regions, except for a single nucleotide polymorphism (SNP) in position 371 in the stx2A subunit (Fig 2). Strain 1108-2781 had an identical q gene to the O111:H− strain (AP010960), but differed from this strain in 14 nucleotides in the region between the q gene and the stx2 gene as well as in the stx2 gene (Fig 2). Additionally, downstream of the stx2 gene, 1108-2781 was different from the O111:H− strain and showed identical sequence to the NSF O157 strain EDL933 (AE005174) (Fig 2). The qO111:H− gene was detected in all SF O157 included in the present study (Table 1).