S1l) (Parkhill et al., 2001). The 17 kb conserved portion of SPI-13 has not been shown to contribute to virulence (Haneda et al., 2009). SPI-14 corresponds to 9 kb present in S. Typhimurium at centisome 19 and is absent in S. Typhi (Shah et al., 2005; Morgan, 2007). It harbours seven ORFs encoding putative cytoplasmic proteins (Fig. S1m). The function of genes on this island is unknown, but gene upregulation was observed in macrophages infected by S. Typhimurium strain SL1344 (Eriksson et al., 2003). SPI-15 is a 6.5 kb island of five ORFs encoding

hypothetical proteins, is inserted near the glyU tRNA gene in S. Typhi and is absent in S. Typhimurium (Fig. S1n) (Vernikos & Parkhill, 2006). Different genes are found at the same location in S. Typhi strain Ty2 (Fig. S1n) (Vernikos & Parkhill, 2006). SPI-15, as well Dabrafenib purchase as SPI-16 and 17, were identified by bioinformatic work (Vernikos & Parkhill, 2006). SPI-16 is found in S. Typhimurium and S. Typhi as a 4.5 kb fragment inserted next to an argU tRNA site, and RG7422 solubility dmso encodes five or seven ORFs, respectively, four of which are pseudogenes in S. Typhi (Fig. S1o). The three remaining ORFs show a high

level of identity with P22 phage genes involved in seroconversion (Vernikos & Parkhill, 2006) and were suggested to mediate O-antigen glycosylation (Mavris et al., 1997; Guan et al., 1999) and cell surface variation (Allison & Verma, 2000; Bogomolnaya et al., 2008). These ORFs (genes yfdH, rfbI and STM0557) were required for the intestinal persistence of S. Typhimurium in mice (Bogomolnaya et al., 2008). SPI-17 is a 5 kb island encoding six ORFs inserted next to an argW tRNA site and is absent in S. Typhimurium, but mafosfamide present in S. Typhi (Fig. S1p) (Vernikos & Parkhill, 2006). Seroconversion genes homologous to P22 phage are present and showed high homology to genes of SPI-16, including a putative lipopolysaccharide modification acyltransferase. Most of these genes (four) are pseudogenes in S. Typhi (Fig. S1p). SPI-18 was recently identified in S. Typhi as a 2.3 kb fragment harbouring only two ORFs: STY1498 and STY1499

(Fig. S1q) (Fuentes et al., 2008). clyA (STY1498), also known as hlyE or sheA, encodes a 34 kDa pore-forming secreted cytolysin found in E. coli and S. enterica serovars Typhi and Paratyphi A (del Castillo et al., 1997; Green & Baldwin, 1997; Oscarsson et al., 1999, 2002). clyA is important for invasion of human epithelial cells in vitro, with its heterologous expression in S. Typhimurium leading to colonization of deep organs in a murine model (Fuentes et al., 2008). taiA (STY1499) is a secreted 27 kDa invasin that increases bacterial uptake by human macrophages (Faucher et al., 2009). Both genes are part of a common operon and are controlled by the virulence-related regulator PhoP (Faucher et al., 2009). Other pathogenicity islands are found in the S. Typhimurium and S.