About Salmonella

General information:
Gram-negative bacilli, comprise two species: S. enterica, which is subdivided into over 2,000 serovars, and S. bongori.
Based on genetic similarity and host range, the species has been divided into six subspecies: enterica (Group 1), salamae (Group 2), arizonae (Group 3a), diarizonae (Group 3b), houtenae (Group 4), and indica (Group 6). S. bongori was initially categorized as subspecies 5.
enterica includes many of the serotypes pathogenic for humans, including S. typhi and S. typhimurium.
Characteristics:
Traverse the intestinal mucosa through M cells, colonize Peyer's pathes, spread via the lymphatics and bloodstream to the liver and speen.
Mode of entry: trigger mechanism and zipper mechanism.
In contrast to Shigella, Listeria and Richettsiae, which escape from their nascent membrane-bound compartment and replicate in the cytoplasm, Salmonella manages to survive within its membrane-bound vacuole.
Disease:
S. typhimurium: a leading cause of human gastroenteritis, and is used as a mouse model of human typhoid fever.
S. typhi: a human-specific pathogen causing the systemic febrile illness typhoid fever.
Selected genomes: ⇒ comparative pathogenomics ⇐
S. enterica subsp. arizonae serovar 62:z4,z23:-- str. RSK2980, 4600800 bp, NC_010067
S. enterica subsp. enterica serovar Agona str. SL483, 4798660 bp, NC_011149
S. enterica subsp. enterica serovar Choleraesuis str. SC-B67, 4755700 bp, NC_006905
S. enterica subsp. enterica serovar Dublin str. CT_02021853, 4842908 bp, NC_011205
S. enterica subsp. enterica serovar Enteritidis str. P125109, 4685848 bp, NC_011294
S. enterica subsp. enterica serovar Gallinarum str. 287/91, 4658697 bp, NC_011274
S. enterica subsp. enterica serovar Heidelberg str. SL476, 4888768 bp, NC_011083
S. enterica subsp. enterica serovar Newport str. SL254, 4827641 bp, NC_011080
S. enterica subsp. enterica serovar Paratyphi A str. AKU_12601, 4581797 bp, NC_011147
S. enterica subsp. enterica serovar Paratyphi A str. ATCC 9150, 4585229 bp, NC_006511
S. enterica subsp. enterica serovar Paratyphi B str. SPB7, 4858887 bp, NC_010102
S. enterica subsp. enterica serovar Paratyphi C strain RKS4594, 4833080 bp, NC_012125
S. enterica subsp. enterica serovar Schwarzengrund str. CVM19633, 4709075 bp, NC_011094
S. enterica subsp. enterica serovar Typhi str. CT18, 4809037 bp, NC_003198
S. enterica subsp. enterica serovar Typhi str. Ty2, 4791961 bp, NC_004631
S. enterica subsp. enterica serovar Typhimurium str. LT2, 4857432 bp, NC_003197
Plasmids:
S. enterica subsp. enterica serovar Choleraesuis str. SC-B67 pSCV50, 49558 bp, NC_006855
S. enterica subsp. enterica serovar Dublin str. CT_02021853 pCT02021853_74, 74551 bp, NC_011204
S. enterica subsp. enterica serovar Paratyphi C strain RKS4594 pSPCV, 55414 bp, NC_012124
S. enterica subsp. enterica serovar Typhimurium str. LT2 pSLT, 93939 bp, NC_003277
Related publications:
Parkhill J, et al., 2001. Complete genome sequence of a multiple drug resistant Salmonella enterica serovar Typhi CT18. Nature 413(6858):848-852.
McClelland M, et al., 2001. Complete genome sequence of Salmonella enterica serovar Typhimurium LT2. Nature 413(6858):852-856.
Deng W, et al., 2003. Comparative genomics of Salmonella enterica serovar Typhi strains Ty2 and CT18. J. Bacteriol. 185(7):2330-2337.
McClelland M, et al., 2004. Comparison of genome degradation in Paratyphi A and Typhi, human-restricted serovars of Salmonella enterica that cause typhoid. Nat Genet 36(12):1268-1274.
Chiu CH, et al., 2005. The genome sequence of Salmonella enterica serovar Choleraesuis, a highly invasive and resistant zoonotic pathogen. Nucleic Acids Res 33(5):1690-1698.
Welch TJ, et al., 2007. Multiple antimicrobial resistance in plague: an emerging public health risk. PLoS One 2(3):e309.
Thomson NR, et al., 2008. Comparative genome analysis of Salmonella Enteritidis PT4 and Salmonella Gallinarum 287/91 provides insights into evolutionary and host adaptation pathways. Genome Res 18(10):1624-1637.
Holt KE, et al., 2009. Pseudogene accumulation in the evolutionary histories of Salmonella enterica serovars Paratyphi A and Typhi. BMC Genomics 10:36.
Liu WQ, et al., 2009. Salmonella paratyphi C: genetic divergence from Salmonella choleraesuis and pathogenic convergence with Salmonella typhi. PLoS One 4(2):e4510.
Major virulence factors in Salmonella:
Adherence
Agf (Thin aggregative fimbriae (or curli))
Lpf (Long polar fimbriae)
MisL
Pef (Plasmid-encoded fimbriae)
RatB
ShdA
SinH
Type 1 fimbriae
Effector delivery system
SCI (Salmonella centrisome island)
SCI T6SS secreted effectors
TTSS (SPI-1 encode)
TTSS (SPI-2 encode)
TTSS effectors secreted via both systems
TTSS-1 secreted effectors
TTSS-2 secreted effectors
Exotoxin
SpvB
Typhoid toxin - S. enterica serovar typhi
Immune modulation
Rck (Resistance to complement killing)
Vi antigen - S. enterica serovar typhi
Nutritional/Metabolic factor
MgtBC
Stress survival
SodCI
Antimicrobial activity/Competitive advantage
Mig-14 (Macrophage-inducible gene-14)
Mig-5 (Macrophage-inducible gene-5)
Regulation
Fur (Ferric uptake regulator)
PhoPQ
PmrAB
QseBC
RpoS
SsrAB

Genomic location of virulence-related genes in Salmonella:

Terms

M cells

Specialized cells devoid of brush border which belong to the follicle-associated epithelium(FEA) that covers the lymph nodes associated with the mucosa. It spares the microbe the need to dissolve the mucus, resist intestinal peristaltism, invade epithelial cells through their apical brush border, or penetrate between cells by opening their tight junctions;The major Gram-negative enteroinvasive pathogens, Shigella, Salmonella, and Yersinia, primarily use the FAE as their entry route.

trigger mechanism
Contact between bacteria and cells results in a dramatic response at the cell surface and bacterial uptake via membrane ruffles, a process resembling macropinocytosis. This mode of entry into non-professional phagocytes is empolyed by Salmonella and Shigella

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