Table 1.
Current understanding of the size, function, and distribution of Salmonella pathogenicity islands (SPIs) among Salmonella.
| SPI1 | Size/location2 (kb) | Main genes or gene products3 | Proposed function | Relative distribution4,5 | References |
|---|---|---|---|---|---|
| SPI-1 | 40 | T3SS, effector proteins (e.g., avrA, iacB, invB, sicA, sicP, sipA, sipB, sipC, and sptP) | Host cell invasion and enteropathy | S. enterica S. bongori | Fookes et al., 2011; Cao et al., 2013; Fàbrega and Vila, 2013 |
| SPI-2 | 40 | T3SS, effector proteins (ssaB, ssaE, sscA, sscB, sseA, sseF, sseG, and ttr genes) | Intracellular survival |
S. enterica subsp. enterica S. enterica subsp. salamae S. enterica subsp. diarizonae S. enterica subsp. indica |
Fookes et al., 2011; Fàbrega and Vila, 2013 |
| SPI-3 | Variable (17–36) | Magnesium transport system (mgtCB), misL | Intracellular survival, intestinal colonization |
S. enterica subsp. enterica S. enterica subsp. salamae S. enterica subsp. arizonae (partial) S. enterica subsp. diarizonae (partial) S. enterica subsp. houtenae (partial) S. enterica subsp. indica S. bongori |
Dorsey et al., 2005; Sabbagh et al., 2010; Fookes et al., 2011; Kaur and Jain, 2012 |
| SPI-4 | 25 | T1SS (siiABCDF), non-fimbrial adhesin (siiE) | Adhesion and invasion of epithelial cells, virulence in mice and cows |
S. enterica subsp. enterica S. enterica subsp. houtenae S. enterica subsp. indica S. bongori |
Morgan et al., 2007; Sabbagh et al., 2010; Fookes et al., 2011 |
| SPI-5 | Variable (11–44) | Effectors of SPI-1 and -2 (pipABC, sopB, pipD, and sigDE) | Epithelial invasion, enteric salmonellosis, and chicken colonization | S. enterica subsp. enterica | Fookes et al., 2011; Shah et al., 2012; Fàbrega and Vila, 2013; Cao et al., 2014 |
| SPI-6 | Variable (47–59) | T6SS, atypical fimbriae (safABCD), fimbriae (tcfABCD), and sciS | Invasion, intramacrophage survival, chicken colonization, and virulence in mice |
S. enterica subsp. enterica S. enterica subsp. salamae (partial) S. enterica subsp. arizonae (partial) S. enterica subsp. diarizonae (partial) S. enterica subsp. houtenae (partial) S. enterica subsp. indica (partial) |
Parkhill et al., 2001; Fookes et al., 2011; Cao et al., 2014; Pezoa et al., 2014 |
| SPI-7 | 134 | Vi capsule biosynthesis genes, SopE prophage, and type IVb pilus | Vi exopolysaccharide, host immune modulation, and intramacrophage survival | S. enterica subsp. enterica serovars Typhi, Paratyphi C, Dublin | Pickard et al., 2003; Faucher et al., 2005; Fookes et al., 2011 |
| SPI-8 | 6.8 | Bacteriocin fragment | Unknown | S. enterica subsp. enterica | Faucher et al., 2005; Saroj et al., 2008; Sabbagh et al., 2010; Fookes et al., 2011; Desai et al., 2013 |
| SPI-9 | 16 | T1SS, adhesin | Transport, epithelial adherence |
S. enterica subsp. enterica S. enterica subsp. salamae S. enterica subsp. arizonae S. enterica subsp. diarizonae S. enterica subsp. houtenae S. enterica subsp. indica S. bongori |
Sabbagh et al., 2010; Fookes et al., 2011; Velasquez et al., 2016 |
| SPI-10 | 33 | P4-like prophage, Sef fimbriae | Virulence in mice and chickens, intramacrophage uptake or survival | S. enterica subsp. enterica | Parkhill et al., 2001; Bishop et al., 2005; Sabbagh et al., 2010 |
| SPI-11 | Variable (6–10) | pagCD, envF (some) sRNA RaoN, typhoid toxin gene islet (cdtB, pltA, and pltB) (some) | Intramacrophage survival, serum resistance, and typhoid fever pathology | S. enterica subsp. enterica | Sabbagh et al., 2010; Fookes et al., 2011; Lee et al., 2013 |
| SPI-12 | Variable (6–15) | sspH2 | Actin polymerization, virulence in mice | S. enterica subsp. enterica | Morgan, 2007; Fookes et al., 2011; Tomljenovic-Berube et al., 2013 |
| SPI-13 | 25 | putative lyase, hydrolase, oxidase, and arylsulphatase regulator | Macrophage internalization, virulence in chickens, and mice |
S. enterica subsp. enterica (NTS) S. enterica subsp. arizonae S. enterica subsp. diarizonae S. enterica subsp. houtenae (some) |
Shah et al., 2005; Sabbagh et al., 2010; Fookes et al., 2011; Elder et al., 2016; Espinoza et al., 2017 |
| SPI-14 | 9 | gpiAB, putative acyl-CoA dehydrogenase | Chicken pathogenicity, epithelial invasion |
S. enterica subsp. enterica (NTS) S. enterica subsp. arizonae S. enterica subsp. houtenae (some) |
Shah et al., 2005, 2012; Fookes et al., 2011 |
| SPI-15 | 6.5 | Four putative ORFs | Unknown | S. enterica subsp. enterica serovar Typhi | Vernikos and Parkhill, 2006; Fookes et al., 2011 |
| SPI-16 | 4.5 | Bactoprenol glucosyl transferase and translocase (gtrAB) | LPS modification, seroconversion | S. enterica subsp. enterica | Vernikos and Parkhill, 2006; Fookes et al., 2011 |
| SPI-17 | 5 | Bactoprenol glucosyl transferase and translocase (gtrAB) | LPS modification, seroconversion | S. enterica subsp. enterica | Vernikos and Parkhill, 2006; Fookes et al., 2011 |
| SPI-18 | 2.3 | hlyE hemolysin, taiA invasion-associated protein | Epithelial invasion |
S. enterica subsp. enterica S. enterica subsp. diarizonae |
Den Bakker et al., 2011; Fookes et al., 2011 |
| SPI-19 | 45 | T6SS | Intramacrophage survival, chicken colonization | S. enterica subsp. enterica | Fookes et al., 2011; Blondel et al., 2013; Pezoa et al., 2014 |
| SPI-20 | 34 | T6SS | Unknown | S. enterica subsp. arizonae | Blondel et al., 2009, 2013; Fookes et al., 2011 |
| SPI-21 | 55 | T6SS | Unknown | S. enterica subsp. arizonae | Blondel et al., 2009, 2013; Fookes et al., 2011 |
| SPI-22 | 20 | T6SS | Unknown | S. bongori | Fookes et al., 2011 |
| SPI-23 | 37 | T3SS effectors (sanA, chlR, shaU, and dumE) | Host cell adherence and invasion, invasion of pig epithelial cells | S. enterica subsp. enterica | Hayward et al., 2013, 2014 |
| SPI-24/CS54 | 25 | Outer membrane protein (shdA, sivH, ratAB, sinI, and potR) | Fibronectin binding, murine intestinal colonization, and intramacrophage survival | S. enterica subsp. enterica | Kingsley et al., 2003; Sabbagh et al., 2010 |
1SPI-10 was initially defined in S. Typhi and was thought to be unique to S. Typhi (Sabbagh et al., 2010), although other studies have reported the presence of SPI-10 genes in NTS serovars as well (Den Bakker et al., 2011; Desai et al., 2013). 2In some cases the size varies between serovars depending on the number of genes encoded. 3“some” indicates that not all serovars, or strains within a serovar, carry a given gene(s). 4Distribution based on screening of few representative strains, may not be representative of the entire subspecies as comprehensive studies for all serovars have not been conducted. For SPIs 5 and 11 no data were available for testing in subspecies other than enterica.5“Partial” indicates that strains tested in the labeled subspecies encoded part of the SPI, but not the full SPI.