The stx2 gene is required for EHEC to kill germ-free mice (Eaton et al., 2008). Hemolysins are encoded by ehxCABD genes on the plasmid pO157 (Saitoh et al., 2008). These factors damage cultured intestinal epithelial ZD1839 chemical structure cells (Obrig et al., 1988; Figueiredo et al., 2003). Bacterial motility and adherence to intestinal epithelial cells are considered to contribute to EHEC virulence (Levine et al., 1983; Holden & Gally, 2004). Expression of the flhDC gene, which encodes a transcription

factor of flagellar genes, is activated when EHEC encounters nutrients (Tobe et al., 2011). EHEC attachment to intestinal epithelial cells forms attaching and effacing lesions. The locus of enterocyte effacement (LEE), a pathogenicity island of the EHEC genome, encodes many genes involved in the formation of attaching and effacing lesions. LEE contains the eae locus, which encodes a cell adhesive protein termed intimin (Jerse et al., 1991; Frankel et al., 1998). LEE also encodes the transcription factors Ler, GrlR, and GrlA, which regulate expression of the LEE genes (Elliott et al., 2000; Barba et al., 2005). Expression of the LEE genes is also regulated by PchA, PchB, PchC, and LrhA, which are encoded in other genome loci (Iyoda & Watanabe, 2004; Honda et al., 2009). LrhA not only activates the expression of LEE genes, but also activates the expression of the ehxCABD, which

encodes enterohemolysin and inactivates the expression of flagellar genes; thus, it is thought to function as a switch to change the physiologic status of EHEC from a translocating phase to an adherence and toxin-producing phase (Lehnen et al., Selumetinib clinical trial 2002; Honda et al., 2009; Iyoda et al., 2011). Although many EHEC O157:H7 genes are known to be involved in producing toxins, adherence and motility, it has not yet been investigated either whether these factors, other than Shiga toxin 2, contribute to animal killing by EHEC. EHEC O157:H7 possesses the O157 antigen on lipopolysaccharide (LPS). The LPS O-antigen in several Gram-negative bacteria, such as Shigella (West

et al., 2005), Yersinia (Skurnik & Bengoechea, 2003), Salmonella (Ho et al., 2008), Burkholderia (Loutet et al., 2006), and Actinobacillus (Ramjeet et al., 2005), has a defensive role against host antimicrobial peptides. The LPS O-antigen of EHEC O157:H7 comprises N-acetyl-d-perosamine, l-fucose, d-glucose, and N-acetyl-d-galactose (Perry et al., 1986). N-acetyl-d-galactose is synthesized from galactose by GalE, GalT, GalK, and GalU (Genevaux et al., 1999). The galETKM deletion mutant of EHEC O157:H7, which has little O-antigen, has attenuated ability to colonize the infant rabbit intestine and is sensitive to antimicrobial polypeptides (Ho & Waldor, 2007). l-Fucose and N-acetyl-d-perosamine are monosaccharides specific for the LPS O-antigen (Wang & Reeves, 1998; Shimizu et al., 1999). Perosamine is found in the O-antigen of Vibrio cholerae O1, E. coli O157:H7, and Brucella spp. (Wu & Mackenzie, 1987; Samuel & Reeves, 2003).