Following colonization, intimate adherence, and pedestal formation by EHEC, the clinical syndrome progresses from watery diarrhea to hemorrhagic colitis. At this stage, StcE plays an anti-inflammatory role by localizing the human complement regulator, C1 esterase inhibitor (C1-INH), to cell surfaces, decreasing the complement-mediated lysis of both bacteria and host cells (Lathem et al., 2004; Grys et al., 2006). Shigella, another enteropathogen, is indistinguishable from E. coli by DNA–DNA hybridization techniques, Hydroxychloroquine order with

the exception of Shigella boydii 13 (Shigella B13) (Pupo et al., 2000). Shigella B13 is more closely related to Escherichia albertii than the E. coli–Shigella group and lacks the large virulence plasmid, (pINV), that confers the invasion phenotype in all other Shigella. Hyma et al. (2005) demonstrated

that Shigella B13 and E. albertii strains carry eae, a marker for LEE. A small subset of analyzed Shigella B13 strains encoding eae were more related to the E. coli–Shigella group and labeled atypical Shigella B13. Many of these strains also carried markers for the pO157 plasmid, such as ehxA and toxB, suggesting that atypical Shigella B13 may be similar to EHEC and, thus, may encode stcE. This study describes the identification of stcE in atypical Shigella B13 strains and the genetic and phenotypic profile of this unique cluster of Shigella. The S. boydii 7 and 13 and E. albertii strains used in this study are listed in Table 2 and were provided by Thomas Whittam. Escherichia coli O157:H7 EDL933 and CHIR99021 E. coli O127:H6 E2348/69 were provided by Alison O’Brien. Escherichia coli K12 MG1655 and S. flexneri 5a M90T were provided from Fred Blattner. Internal fragments of Shigella (Venkatesan et al., 2001) and E. coli (Burland et al., 1998) genes were amplified using the primers shown in Table 1. Strains stored at −80 °C in Luria–Bertani (LB) medium with 50% glycerol were directly inoculated into PCRs with GoTaq polymerase (Promega). The stcE gene was sequenced from PCR products amplified with primers IR ApaI 5′ 1 and etpD 3′ 1803 (Table 1) and TripleMaster polymerase (Eppendorf) from plasmid DNA

extracted from the atypical Shigella B13 strains using a Maxi Prep Kit (Qiagen). The nucleotide sequence for the stcE gene from the atypical Shigella B13 strains 3556-77, 3557-77, 3052-94, Digestive enzyme and 3053-94 have been submitted to GenBank under accession numbers EU159265, EU159266, EU159267, and EU159268, respectively. For Southern blot analysis, plasmid DNA isolated from the atypical Shigella B13 strains was electrophoresed on a 0.6% agarose gel. Gel and stcE probe preparation and hybridization were performed as previously described (Lathem et al., 2003). 5′-AAGGGCCCCTCTGAGGTGTCTGTTAAA CCCGTGG-3 To examine the secretion of StcE, strains were grown in 25 mL Lennox L broth overnight at 37 °C with aeration and cells removed by centrifugation.