Salmonella enterica subsp. enterica

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Salmonella enterica
Salmonella enterica serovar typhimurium 01.jpg
Salmonella Typhimurium colonies on a Hektoen enteric agar plate
Scientific classification
Kingdom: Bacteria
Phylum: Proteobacteria
Class: Gammaproteobacteria
Order: Enterobacteriales
Family: Enterobacteriaceae
Genus: Salmonella
Species: S. enterica
Subspecies: S. e. subsp. enterica
Trinomial name
Salmonella enterica subsp. enterica
Serovar
  • Salmonella Choleraesuis
  • Salmonella Dublin
  • Salmonella Enteritidis
  • Salmonella Heidelberg
  • Salmonella Paratyphi
  • Salmonella Typhi
  • Salmonella Typhimurium

Salmonella enterica subsp. enterica is a subspecies of Salmonella enterica, the rod-shaped, flagellated, aerobic, Gram-negative bacterium. Many of the pathogenic serovars of the S. enterica species are in this subspecies, including that responsible for typhoid.[1]

Serovars[edit]

S. enterica subsp. enterica contains a large number of serovars which can infect a broad range of vertebrate hosts. The individual members range from being highly host-adapted (only able to infect a narrow range of species) to displaying a broad host range. A number of techniques are currently used to differentiate between serotypes. These include looking for the presence or absence of antigens, phage typing, molecular fingerprinting and biotyping, where serovars are differentiated by which nutrients they are able to ferment. A possible factor in determining the host range of particular serovars is phage-mediated acquisition of a small number of genetic elements that enable infection of a particular host.[2] It is further postulated that serovars which infect a narrow range of species have diverged from ancestors with a broad host range, and have since specialised and lost the ability to infect some hosts.[3]

A selection of serovars, with known hosts listed. Since there are more than 2500 serovars of Salmonella enterica subsp. enterica, this list is incomplete.

Serovar Host species
Salmonella Choleraesuis Swine
Salmonella Dublin Cattle
Salmonella Enteritidis Humans, rodents, galliformes
Salmonella Gallinarum Galliformes
Salmonella Hadar Humans, galliformes, rabbits
Salmonella Heidelberg Humans, galliformes, swine[4]
Salmonella Infantis Humans, poultry
Salmonella Paratyphi Humans
Salmonella Typhi Humans
Salmonella Typhimurium Infects humans, cattle, swine, sheep, horses, rodents, galliformes

A study of data from 37 countries collected between 2001 and 2007 found that the most common serovar of Salmonella isolated from human cases was Enteritidis, found in an average of 43.5% of cases, followed by Typhimurium (17.1% of cases), Newport (3.5%), Infantis (1.8%), Virchow (1.5%), Hadar (1.5%), and Agona (0.8%).[5]

One strain of Salmonella that has recently been emerging in the United States is Salmonella javiana. "An outbreak occurred in 2002, there were 141 cases that occurred among the participants of the U.S. Transplant Games. Out of the 141 cases, most of the cases were either transplant recipients (34%) or people receiving immunosuppressive therapy (32%)". There is an increasing number of Salmonella serotypes that are multidrug resistant (MDR), which was identified by the CDC's National Antimicrobial Resistance Monitoring System.[6] "Salmonella javiana causes 4% of nontyphodial Salmonella infections in the United States each year."[7]

Metabolism[edit]

Genetic evidence suggests that the serovars can be divided into two groups – one which causes enteric infection and has a broad repertoire of metabolic capabilities, and one which usually causes invasive infection, often in a narrow range of hosts, and shows degradation of anaerobic metabolic pathways. It is thought that these metabolic capabilities are important for obtaining nutrients in the challenging and nutrient-limited inflamed gut environment.[8]

Nomenclature[edit]

The serovars can be designated fully or in a shortened form.[9] The short form lists the genus, Salmonella, which is followed by the capitalized and non-italicized serovar. The full designation for Salmonella Typhi is Salmonella enterica subsp. enterica, serovar Typhi. Each serovar can have many strains, as well, which allows for a rapid increase in the total number of antigenically variable bacteria.[10]

Epidemiology[edit]

Invasive strains of non-typhoidal salmonella, such as Salmonella Typhimurium ST313 have recently been labelled as causing emerging diseases in Africa. Key host immune deficiencies associated with HIV, malaria and malnutrition have contributed to a wide spread of this disease and the need to use expensive antimicrobial drugs in the poorest health services in the world.[11] But also bacterial factors, such as upregulated activity of the virulence gene pgtE, due to a single nucleotide polymorphism (SNP) in its promoter region, have been shown to have a great impact upon the pathogenesis of this particular Salmonella sequence type.[12]

References[edit]

  1. ^ Murray PR, Rosenthal KS, Pfaller MA (2009). Medical Microbiology (6th ed.). Philadelphia, PA: Mosby Elsevier. p. 307. 
  2. ^ Sternlicht M, Staaby J, Sullivan I (December 1975). "Birth order, maternal age, and mental retardation". Mental Retardation. 13 (6): 3–6. doi:10.1128/IAI.70.5.2249-2255.2002. PMC 127920Freely accessible. 
  3. ^ Langridge GC, Fookes M, Connor TR, Feltwell T, Feasey N, Parsons BN, Seth-Smith HM, Barquist L, Stedman A, Humphrey T, Wigley P, Peters SE, Maskell DJ, Corander J, Chabalgoity JA, Barrow P, Parkhill J, Dougan G, Thomson NR (January 2015). "Patterns of genome evolution that have accompanied host adaptation in Salmonella". Proceedings of the National Academy of Sciences of the United States of America. 112 (3): 863–8. doi:10.1073/pnas.1416707112. PMC 4311825Freely accessible. PMID 25535353. 
  4. ^ "Snapshots of Salmonella Serotypes" (PDF). Centers for Disease Control and Prevention. CDC. 
  5. ^ Hendriksen RS, Vieira AR, Karlsmose S, Lo Fo Wong DM, Jensen AB, Wegener HC, Aarestrup FM (August 2011). "Global monitoring of Salmonella serovar distribution from the World Health Organization Global Foodborne Infections Network Country Data Bank: results of quality assured laboratories from 2001 to 2007". Foodborne Pathogens and Disease. 8 (8): 887–900. doi:10.1089/fpd.2010.0787. PMID 21492021. 
  6. ^ Goldrick, Barbara (March 2003). "Emerging Infections: Foodborne Diseases". The American Journal of Nursing. 103 (3): 105–106. doi:10.1097/00000446-200303000-00043. JSTOR 29745004. 
  7. ^ Elward A, Grim A, Schroeder P, Kieffer P, Sellenriek P, Ferrett R, Adams HC, Phillips V, Bartow R, Mays D, Lawrence S, Seed P, Holzmann-Pazgal G, Polish L, Leet T, Fraser V (June 2006). "Outbreak of Salmonella javiana infection at a children's hospital". Infection Control and Hospital Epidemiology. 27 (6): 586–92. doi:10.1086/506483. JSTOR 10.1086/506483. PMID 16755478. 
  8. ^ Nuccio SP, Bäumler AJ (March 2014). "Comparative analysis of Salmonella genomes identifies a metabolic network for escalating growth in the inflamed gut". mBio. 5 (2): e00929–14. doi:10.1128/mBio.00929-14. PMID 24643865. 
  9. ^ "Salmonella nomenclature". March 19, 2005. Archived from the original on 2006-04-15. 
  10. ^ "Salmonella spp. comparative sequencing". Archived from the original on 2007-11-14. 
  11. ^ Feasey NA, Dougan G, Kingsley RA, Heyderman RS, Gordon MA (June 2012). "Invasive non-typhoidal salmonella disease: an emerging and neglected tropical disease in Africa". Lancet. 379 (9835): 2489–99. doi:10.1016/s0140-6736(11)61752-2. PMC 3402672Freely accessible. PMID 22587967. 
  12. ^ Hammarlöf DL, Kröger C, Owen SV, Canals R, Lacharme-Lora L, Wenner N, Schager AE, Wells TJ, Henderson IR, Wigley P, Hokamp K, Feasey NA, Gordon MA, Hinton JC (March 2018). "Salmonella". Proceedings of the National Academy of Sciences of the United States of America. 115 (11): E2614–E2623. doi:10.1073/pnas.1714718115. PMC 5856525Freely accessible. PMID 29487214.