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{{About|the bacterium|the disease|Salmonellosis}} |
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{{Italic title}} |
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{{Taxobox |
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| name = ''Salmonella'' |
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| image = SalmonellaNIAID.jpg |
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| domain = [[Bacteria]] |
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| regnum = [[Eubacteria]] |
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| phylum = [[Proteobacteria]] |
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| classis = [[Gammaproteobacteria]] |
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| ordo = [[Enterobacteriales]] |
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| familia = [[Enterobacteriaceae]] |
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| genus = '''''Salmonella''''' |
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| genus_authority = Lignieres 1900 |
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| subdivision_ranks = Species |
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| subdivision =''[[Salmonella bongori|S. bongori]]''<br /> |
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''[[Salmonella enterica|S. enterica]]'' |
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}} |
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'''''Salmonella''''' {{IPAc-en|ˌ|s|æ|l|m|ə|ˈ|n|ɛ|l|ə}} is a [[genus]] of [[bacillus (shape)|rod-shaped]] (bacillus) [[gram-negative]] [[bacteria]] of the [[Enterobacteriaceae]] family. The two species of ''Salmonella'' are ''[[Salmonella enterica]]'' and ''[[Salmonella bongori]]''. ''Salmonella enterica'' is the type species and is further divided into six [[subspecies]]<ref name=Su>{{cite journal|last1=Su|first1=LH|last2=Chiu|first2=CH|title=Salmonella: clinical importance and evolution of nomenclature.|journal=Chang Gung medical journal|date=2007|volume=30|issue=3|pages=210–9|pmid=17760271}}</ref> that include over 2,500 [[serotype]]s. |
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''S. enterica'' subspecies are found worldwide in all [[warm-blooded]] animals, and in the environment. ''S. bongori'' is restricted to [[ectotherm|cold-blooded animals]], particularly [[reptile]]s.<ref name=Baron>{{cite book | author = Tortora GA | title =Microbiology: An Introduction]| edition = 9th|publisher =Pearson|year =2008|pages=323–324|isbn = 8131722325 |url=https://books.google.com/books?id=TO_vLvPXXeQC&pg=PA323&dq=salmonella+bongori+lizard&hl=en&sa=X&ei=w-YlUfO8I8TPrQeVjoDQDA&ved=0CEcQ6AEwBA#v=onepage&q=salmonella%20bongori%20lizard&f=false }}</ref> |
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Strains of ''Salmonella'' cause illnesses such as [[typhoid fever]], [[paratyphoid fever]], and [[foodborne illness|food poisoning]] ([[salmonellosis]]).<ref name=Sherris>{{cite book | author = Ryan KJ, Ray CG (editors) | title = Sherris Medical Microbiology | edition = 4th | pages=362–8 | publisher = McGraw Hill | year = 2004 | isbn = 0-8385-8529-9 }}</ref> |
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==Traits== |
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''Salmonella'' species are non[[Endospore|spore]]-forming, predominantly [[motility|motile]] [[enterobacteriaceae|enterobacteria]] with cell diameters between about 0.7 and 1.5 [[micrometre|µm]], lengths from 2 to 5 µm, and peritrichous [[flagellum|flagella]] (all around the cell body).<ref name="Fabrega2013">{{cite journal|last1=Fabrega|first1=A.|last2=Vila|first2=J.|title=''Salmonella enterica'' Serovar Typhimurium Skills To Succeed in the Host: Virulence and Regulation|journal=Clinical Microbiology Reviews|volume=26|issue=2|year=2013|pages=308–341|issn=0893-8512|doi=10.1128/CMR.00066-12}}</ref> They are [[chemotrophs]], obtaining their energy from oxidation and reduction reactions using organic sources. They are also [[facultative anaerobic organism|facultative anaerobes]], capable of surviving with or without [[oxygen]].<ref name=Fabrega2013 /> |
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==Taxonomy== |
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The genus ''Salmonella'' is part of the family of [[Enterobacteriaceae]]. Its taxonomy has been revised and has the potential to confuse. The genus comprises two species, ''Salmonella bongori'' and ''Salmonella enterica'', the latter of which is divided into six subspecies: ''S. e. enterica'', ''S. e. salamae'', ''S. e. arizonae'', ''S. e. diarizonae'', ''S. e. houtenae'', and ''S. e. indica''.<ref>{{cite journal|last1=Brenner|first1=FW|last2=Villar|first2=RG|last3=Angulo|first3=FJ|last4=Tauxe|first4=R|last5=Swaminathan|first5=B|title=Salmonella nomenclature.|journal=Journal of clinical microbiology|date=July 2000|volume=38|issue=7|pages=2465–7|pmid=10878026}}</ref><ref>{{cite book|last1=editors|last2=Gillespie|first2=Stephen H.|last3=Hawkey|first3=Peter M.|title=Principles and practice of clinical bacteriology|date=2006|publisher=John Wiley & Sons|location=Hoboken, NJ|isbn=9780470017968|edition=2nd}}</ref> The taxonomic group contains more than 2500 serovars, defined on the basis of the somatic O ([[lipopolysaccharide]]) and flagellar H antigens (the [[Kauffman–White classification]]). The full name of a serovar is given as, for example, ''Salmonella enterica'' subsp. ''enterica'' serovar Typhimurium, but can be abbreviated to ''Salmonella'' Typhimurium. Further differentiation of strains to assist clinicoepidemiological investigation may be achieved by [[antibiogram]] and by supra- or subgenomic techniques such as [[pulsed-field gel electrophoresis]], [[multilocus sequence typing]], and, increasingly, [[whole genome sequencing]]. Historically, salmonellae have been clinically categorized as invasive (typhoidal) or noninvasive (nontyphoidal salmonellae) based on host preference and disease manifestations in humans.<ref>{{cite journal|last1=Okoro|first1=Chinyere K|last2=Kingsley|first2=Robert A|last3=Connor|first3=Thomas R|last4=Harris|first4=Simon R|last5=Parry|first5=Christopher M|last6=Al-Mashhadani|first6=Manar N|last7=Kariuki|first7=Samuel|last8=Msefula|first8=Chisomo L|last9=Gordon|first9=Melita A|last10=de Pinna|first10=Elizabeth|last11=Wain|first11=John|last12=Heyderman|first12=Robert S|last13=Obaro|first13=Stephen|last14=Alonso|first14=Pedro L|last15=Mandomando|first15=Inacio|last16=MacLennan|first16=Calman A|last17=Tapia|first17=Milagritos D|last18=Levine|first18=Myron M|last19=Tennant|first19=Sharon M|last20=Parkhill|first20=Julian|last21=Dougan|first21=Gordon|title=Intracontinental spread of human invasive Salmonella Typhimurium pathovariants in sub-Saharan Africa|journal=Nature Genetics|date=30 September 2012|volume=44|issue=11|pages=1215–1221|doi=10.1038/ng.2423}}</ref> |
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== History == |
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''Salmonella'' was first visualized in 1880 by [[Karl Joseph Eberth|Karl Eberth]] in the Peyer's patches and spleens of typhoid patients.<ref>{{Cite journal|title = Die Organismen in den Organen bei Typhus abdominalis|url = http://link.springer.com/article/10.1007/BF01995472|journal = Archiv für pathologische Anatomie und Physiologie und für klinische Medicin|date = 1880-07-01|issn = 0720-8723|pages = 58–74|volume = 81|issue = 1|doi = 10.1007/BF01995472|language = de|first = Prof C. J.|last = Eberth}}</ref> Four years later in 1884 [[Georg Theodor August Gaffky|Georg Theodor Gaffky]] was able to successfully grow the pathogen in pure culture.<ref>{{Cite journal|title = Food, hygiene, and the laboratory. A short history of food poisoning in Britain, circa 1850-1950|journal = Social history of medicine: the journal of the Society for the Social History of Medicine / SSHM|date = 1999-08-01|issn = 0951-631X|pmid = 11623930|pages = 293–311|volume = 12|issue = 2|first = A.|last = Hardy|doi=10.1093/shm/12.2.293}}</ref> A year after that, medical research scientist [[Theobald Smith]] discovered what would be later known as ''[[Salmonella enterica]]'' (var. Choleraesuis). At the time, Smith was working as a research laboratory assistant in the Veterinary Division of the [[United States Department of Agriculture]]. The department was under the administration of [[Daniel Elmer Salmon]], a veterinary pathologist.<ref name="FDA">{{cite web |url=http://www.cfsan.fda.gov/~dms/a2z-s.html |title= FDA/CFSAN—Food Safety A to Z Reference Guide—Salmonella |work=FDA–Center for Food Safety and Applied Nutrition |archiveurl=https://web.archive.org/web/20090302092542/http://www.cfsan.fda.gov/~dms/a2z-s.html|archivedate=2009-03-02|date=2008-07-03 |accessdate=2009-02-14}}</ref> Initially, ''Salmonella'' Choleraesuis was thought to be the causative agent of [[Classical swine fever|hog cholera]], so Salmon and Smith named it "Hog-cholerabacillus". The name ''Salmonella'' was not used until 1900, when Joseph Leon Lignières proposed that the pathogen discovered by Daniel Salmon's group be called ''Salmonella'' in his honor.<ref name="Deadly Diseases">{{cite book|last1=Heymann|first1=Danielle A. Brands|last2=Alcamo|first2=I. Edward|last3=Heymann|first3=David L.|title=Salmonella|date=2006|publisher=Chelsea House Publishers|location=Philadelphia|isbn=0-7910-8500-7|url=https://books.google.com/books/about/Salmonella.html?id=zASmHprYYnEC|accessdate=31 July 2015}}</ref>{{Rp|16}} |
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==Detection, culture, and growth conditions== |
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Most subspecies of ''Salmonella'' produce [[hydrogen sulfide]],<ref name="BarretClark">{{cite journal |vauthors=Clark MA, Barret EL | title = The ''phs'' gene and hydrogen sulfide production by ''Salmonella typhimurium''.Bacteriology | volume = 169 | issue = 6 | pages = 2391–2397 |date=June 1987 | pmid = | pmc = | doi = 10.1128/jb.169.6.2391-2397.1987| url = http://jb.asm.org/cgi/content/short/169/6/2391 }}</ref> which can readily be detected by growing them on [[growth medium|media]] containing [[ferrous sulfate]], such as is used in the [[TSI slant|triple sugar iron]] test. Most isolates exist in two phases: a motile phase I and a nonmotile phase II. Cultures that are nonmotile upon primary culture may be switched to the motile phase using a [[Craigie tube]] or ditch plate.<ref name=Phase>{{cite journal|title=UK Standards for Microbiology Investigations: Changing the Phase of Salmonella|journal=UK Standards for Microbiology Investigations|date=8 January 2015|pages=8–10|url=https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/394370/TP_32i3.pdf|accessdate=2 August 2015|publisher=Standards Unit, Public Health England}}</ref> |
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''Salmonella'' can also be detected and subtyped using [[Multiplex polymerase chain reaction|multiplex]]<ref>{{Cite journal|title = Development of a Multiplex PCR Technique for Detection and Epidemiological Typing of Salmonella in Human Clinical Samples|url = http://jcm.asm.org/content/42/4/1734|journal = Journal of Clinical Microbiology|date = 2004-04-01|issn = 0095-1137|pmc = 387595|pmid = 15071035|pages = 1734–1738|volume = 42|issue = 4|doi = 10.1128/JCM.42.4.1734-1738.2004|first = Juan|last = Alvarez|first2 = Mertxe|last2 = Sota|first3 = Ana Belén|last3 = Vivanco|first4 = Ildefonso|last4 = Perales|first5 = Ramón|last5 = Cisterna|first6 = Aitor|last6 = Rementeria|first7 = Javier|last7 = Garaizar}}</ref> or [[Real-time polymerase chain reaction|real-time]] [[polymerase chain reaction]]s (PCR)<ref>{{Cite journal|url = http://jcm.asm.org/content/38/9/3429.abstract?ijkey=d9fbc0aba409b6d5e45d9886c0830c83ba75eeec&keytype2=tf_ipsecsha|title = Automated 5′ Nuclease PCR Assay for Identification of Salmonella enterica|last = Hoorfar|first = J.|date = September 2000|journal = Journal of Clinical Microbiology|doi = |pmid = |access-date = 3 August 2015|last2 = Ahrens|first2 = P.|publisher = American Society for Microbiology|volume = 38|issue = 9|pages = 3429–3435}}</ref> from extracted ''Salmonella'' DNA. |
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Mathematical models of ''Salmonella'' growth kinetics have been developed for chicken, pork, tomatoes, and melons.<ref>{{cite journal|author=Dominguez, Silvia A.|title=Modelling the Growth of ''Salmonella'' in Raw Poultry Stored under Aerobic Conditions|url=http://www.ingentaconnect.com/content/iafp/jfp/2008/00000071/00000012/art00008}}</ref><ref>{{cite journal|author=Carmen Pin|title=Modelling ''Salmonella'' concentration throughout the pork supply chain by considering growth and survival in fluctuating conditions of temperature, pH and a|url=https://www.sciencedirect.com/science/article/pii/S0168160510005507?np=y | doi=10.1016/j.ijfoodmicro.2010.09.025|volume=145|journal=International Journal of Food Microbiology|pages=S96–S102}}</ref><ref>{{cite journal|author=Pan, Wenjing|title=Modelling the Growth of Salmonella in Cut Red Round Tomatoes as a Function of Temperature|url=http://www.ingentaconnect.com/content/iafp/jfp/2010/00000073/00000008/art00013}}</ref><ref>{{cite journal|author=Li, Di|title=Development and Validation of a_w Mathematical Model for Growth of Pathogens in Cut Melons|url=http://www.ingentaconnect.com/content/iafp/jfp/2013/00000076/00000006/art00005 | doi=10.4315/0362-028X.JFP-12-398|volume=76|journal=Journal of Food Protection|pages=953–958}}</ref><ref>{{cite web|author=Li, Di|title=Development and validation of a mathematical model for growth of salmonella in cantaloupe|url=http://mss3.libraries.rutgers.edu/dlr/outputds.php?pid=rutgers-lib:37431&mime=application/pdf}}</ref> ''Salmonella'' reproduce asexually with a cell division interval of 40 minutes.<ref name="Deadly Diseases" />{{Rp|16}} |
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''Salmonella'' species lead predominantly host-associated lifestyles, but the bacteria were found to be able to persist in a bathroom setting for weeks following contamination, and are frequently isolated from water sources, which act as bacterial reservoirs and may help to facilitate transmission between hosts.<ref>{{cite journal|last=Winfield|first=Mollie|author2=Eduardo Groisman |title=Role of Nonhost Environments in the Lifestyles of ''Salmonella'' and ''Escerichia coli''|journal=Applied and Environmental Microbiology|date=2003|volume=69|issue=7|pages=3687–3694|doi=10.1128/aem.69.7.3687-3694.2003}}</ref> |
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The bacteria are not destroyed by freezing,<ref>{{cite journal | title = Pathogenicity of Salmonella gallinarum After Metabolic Injury by Freezing | journal = Applied and Environmental Microbiology | date = January 1970 | first = K.M. | last = Sorrells |author2=M. L. Speck |author3=J. A. Warren | volume = 19 | issue = 1 | pages = 39–43| pmid = 5461164 | url = http://aem.asm.org/cgi/content/abstract/19/1/39 | pmc = 376605 | accessdate = 2010-08-19 | quote = Mortality differences between wholly uninjured and predominantly injured populations were small and consistent (5% level) with a hypothesis of no difference.}}</ref><ref>{{cite journal | title = Salmonella Survival on Pecans as Influenced by Processing and Storage Conditions | journal = Applied and Environmental Microbiology | date = June 1975 | first = L. R. | last = Beuchat |author2=E. K. Heaton | volume = 29 | issue = 6 | pages = 795–801| pmid = 1098573 | url = http://aem.asm.org/cgi/content/abstract/29/6/795 | pmc = 187082 | accessdate = 2010-08-19 | quote = Little decrease in viable population of the three species was noted on inoculated pecan halves stored at -18, -7, and 5°C for 32 weeks.}}</ref> but [[Ultraviolet radiation|UV light]] and heat accelerate their destruction. They perish after being heated to {{Convert|55|°C|°F}} for 90 min, or to {{Convert|60|°C|°F}} for 12 min.<ref>{{Cite journal | title = Fate of Salmonella Inoculated into Beef for Cooking | journal= Journal of Food Protection Vol. 41 No.8 | date = August 1978 | first = S.J. | last= Goodfellow |author2=W.L. Brown | volume = 41 | issue = 8 | pages= 598–605}}</ref> To protect against ''Salmonella'' infection, heating food for at least 10 minutes to an internal temperature of {{Convert|75|°C|°F}} is recommended.<ref>[[Partnership for Food Safety Education]] (PFSE) [http://www.fightbac.org/storage/documents/flyers/fightbac_color_brochure.pdf Fight BAC! Basic Brochure].</ref><ref>[[USDA]] [http://www.fsis.usda.gov/PDF/Internal_Cooking_Temperatures_CFG.pdf Internal Cooking Temperatures Chart]. The USDA has other resources available at their [http://www.fsis.usda.gov/fact_sheets/Safe_Food_Handling_Fact_Sheets/index.asp Safe Food Handling] fact-sheet page. See also the [http://www.uga.edu/nchfp/index.html National Center for Home Food Preservation].</ref> |
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''Salmonella'' species can be found in the digestive tracts of humans and animals, especially reptiles. ''Salmonella'' on the skin of reptiles or amphibians can be passed to people who handle the animals.<ref>{{Cite web|url = http://www.cdc.gov/Features/SalmonellaFrogTurtle/index.html|title = Reptiles, Amphibians, and Salmonella|date = 25 November 2013|accessdate = 3 August 2013|website = Centers for Disease Control and Prevention|publisher = U.S. Department of Health & Human Services}}</ref> Food and water can also be contaminated with the bacteria if they come in contact with the feces of infected people or animals.<ref name=Barbara2003>{{cite journal|last1=Goldrick|first1=Barbara|title=Foodborne Diseases: More efforts needed to meet the Healthy People 2010 objectives |
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|journal=The American Journal of Nursing|year=2003|volume=103|issue=3|pages=105–106 |url=http://journals.lww.com/ajnonline/Citation/2003/03000/Foodborne_Diseases__More_efforts_needed_to_meet.43.aspx|accessdate=6 December 2014|doi=10.1097/00000446-200303000-00043}}</ref> |
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== Nomenclature == |
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Initially, each ''Salmonella'' "species" was named according to clinical considerations,<ref>F. Kauffmann: Die Bakteriologie der Salmonella-Gruppe. Munksgaard, Kopenhagen, 1941</ref> for example ''Salmonella typhi-murium'' (mouse typhoid fever), ''S. cholerae-suis''. After it was recognized that host specificity did not exist for many species, new strains received species names according to the location at which the new strain was isolated. Later, molecular findings led to the hypothesis that ''Salmonella'' consisted of only one species,<ref>{{cite journal |author1=Minor L. Le |author2=Popoff M. Y. | year = 1987 | title = Request for an Opinion. Designation of Salmonella enterica. sp. nov., nom. rev., as the type and only species of the genus Salmonella | url = | journal = Int. J. Syst. Bacteriol | volume = 37 | issue = | pages = 465–468 }}</ref> ''S. enterica'', and the serovars were classified into six groups,<ref>{{cite journal | pmid = 2915026 | volume=27 | issue=2 | title=Clonal nature of Salmonella typhi and its genetic relatedness to other salmonellae as shown by multilocus enzyme electrophoresis, and proposal of Salmonella bongori comb. nov | pmc=267299 |date=February 1989 | journal=J. Clin. Microbiol. | pages=313–20 |vauthors=Reeves MW, Evins GM, Heiba AA, Plikaytis BD, Farmer JJ }}</ref> two of which are medically relevant. As this now-formalized nomenclature<ref>{{cite journal | pmid = 15653929 | doi=10.1099/ijs.0.63579-0 | volume=55 | issue=Pt 1 | title=The type species of the genus Salmonella Lignieres 1900 is Salmonella enterica (ex Kauffmann and Edwards 1952) Le Minor and Popoff 1987, with the type strain LT2T, and conservation of the epithet enterica in Salmonella enterica over all earlier epithets that may be applied to this species. Opinion 80 |date=January 2005 | journal=Int. J. Syst. Evol. Microbiol. | pages=519–20}}</ref><ref>{{cite journal | pmid = 15653930 | doi=10.1099/ijs.0.63580-0 | volume=55 | issue=Pt 1 | title=Nomenclature and taxonomy of the genus Salmonella |date=January 2005 | journal=Int. J. Syst. Evol. Microbiol. | pages=521–4 | author=Tindall BJ, Grimont PA, Garrity GM, Euzéby JP}}</ref> is not in harmony with the traditional usage familiar to specialists in microbiology and infectologists, the traditional nomenclature is still common. Currently, the two recognized species are ''[[Salmonella enterica|S. enterica]]'', and ''[[Salmonella bongori|S. bongori]]''. In 2005, a third species, ''Salmonella subterranean'', was proposed, but according to the World Health Organization, the bacterium reported does not belong in the genus ''Salmonella''.<ref name=Pasteur>{{cite book|last1=Grimont|first1=Patrick A.D.|last2=Xavier Weill|first2=François|title=Antigenic Formulae of the Salmonella Serovars|date=2007|publisher=WHO Collaborating Centre for Reference and Research on Salmonella|location=Institut Pasteur, Paris, France|page=7|edition=9th|url=http://www.scacm.org/free/Antigenic%20Formulae%20of%20the%20Salmonella%20Serovars%202007%209th%20edition.pdf|accessdate=26 August 2015}}</ref> The six main recognised subspecies are: ''enterica'' (serotype I), ''salamae'' (serotype II), ''arizonae'' (IIIa), ''diarizonae'' (IIIb), ''houtenae'' (IV), and ''indica'' (VI).<ref>Janda JM, Abbott SL (2006). "The Enterobacteria", ASM Press.</ref> The former serotype (V) was ''bongori'', which is now considered its own species. |
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The serovar, or serotype, is a classification of ''Salmonella'' into subspecies based on antigens that the organism presents. It is based on the [[Kauffman-White classification]] scheme that differentiates serological varieties from each other. Serotypes are usually put into subspecies groups after the genus and species, with the serovars/serotypes capitalized, but not italicized: An example is ''Salmonella enterica'' serovar Typhimurium. More modern approaches for typing and subtyping ''Salmonella'' include DNA-based methods such as [[pulsed field gel electrophoresis]], [[Multiple Loci VNTR Analysis|multiple-loci VNTR analysis]], [[multilocus sequence typing]], and multiplex-[[PCR]]-based methods.<ref name= PorwollikS>{{cite book | author= Porwollik, S (editor) | year=2011 | title=Salmonella: From Genome to Function | publisher=[[Caister Academic Press]] | isbn= 978-1-904455-73-8}}</ref><ref name=Achtman2012>{{Cite journal | last1 = Achtman | first1 = M. | authorlink1 = Mark Achtman| last2 = Wain | first2 = J. | last3 = Weill | first3 = F. O. X. | last4 = Nair | first4 = S. | last5 = Zhou | first5 = Z. | last6 = Sangal | first6 = V. | last7 = Krauland | first7 = M. G. | last8 = Hale | first8 = J. L. | last9 = Harbottle | first9 = H. | last10 = Uesbeck | first10 = A. | last11 = Dougan | first11 = G. | authorlink11 = Gordon Dougan| last12 = Harrison | first12 = L. H. | last13 = Brisse | first13 = S. | author14 = S. Enterica MLST Study Group | editor1-last = Bessen | editor1-first = Debra E | title = Multilocus Sequence Typing as a Replacement for Serotyping in Salmonella enterica | doi = 10.1371/journal.ppat.1002776 | journal = [[PLOS Pathogens]]| volume = 8 | issue = 6 | pages = e1002776 | year = 2012 | pmid = 22737074| pmc =3380943 }} {{open access}}</ref> |
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== As pathogens == |
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''Salmonella'' species are facultative [[intracellular pathogen]]s.<ref>{{Cite journal |
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| last1 = Jantsch | first1 = J. |
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| last2 = Chikkaballi | first2 = D. |
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| last3 = Hensel | first3 = M. |
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| title = Cellular aspects of immunity to intracellular Salmonella enterica |
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| doi = 10.1111/j.1600-065X.2010.00981.x |
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| journal = Immunological Reviews |
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| volume = 240 |
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| issue = 1 |
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| pages = 185–195 |
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| year = 2011 |
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| pmid = 21349094 |
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}}</ref> Many infections are due to ingestion of contaminated food. ''Salmonella'' serovars can be divided into two main groups—typhoidal and nontyphoidal ''Salmonella''. Nontyphoidal serovars are more common, and usually cause self-limiting gastrointestinal disease. They can infect a range of animals, and are [[zoonotic]], meaning they can be transferred between humans and other animals. Typhoidal serovars include ''Salmonella'' Typhi and ''Salmonella'' Paratyphi A, which are adapted to humans and do not occur in other animals. |
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== Nontyphoidal ''Salmonella''== |
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{{See also|Salmonellosis}} |
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Infection with nontyphoidal serovars of ''Salmonella'' generally results in food poisoning. Infection usually occurs when a person ingests foods that contain a high concentration of the bacteria. Infants and young children are much more susceptible to infection, easily achieved by ingesting a small number of bacteria. In infants, infection through inhalation of bacteria-laden dust is possible. |
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The organisms enter through the digestive tract and must be ingested in large numbers to cause disease in healthy adults. An infection can only begin after living salmonellae (not merely ''Salmonella''-produced toxins) reach the gastrointestinal tract. Some of the microorganisms are killed in the stomach, while the surviving ones enter the small intestine and multiply in tissues. Gastric acidity is responsible for the destruction of the majority of ingested bacteria, but ''Salmonella'' has evolved a degree of tolerance to acidic environments that allows a subset of ingested bacteria to survive.<ref>{{cite journal|last=Garcia-del Portillo|first=Francisco|author2=John W. Foster |author3=Brett Finlay |title=Role of Acid Tolerance Response Genes in Salmonella tymphimurium Virulence|journal=Infection and Immunity|year=1993|volume=61|issue=10|pages=4489–4492}}</ref> Bacterial colonies may also become trapped in mucus produced in the oesophagus. By the end of the incubation period, the nearby host cells are poisoned by [[Lipopolysaccharide|endotoxins]] released from the dead salmonellae. The local response to the endotoxins is enteritis and gastrointestinal disorder. |
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About 2,000 serotypes of nontyphoidal ''Salmonella'' are known, which may be responsible for as many as 1.4 million illnesses in the United States each year. People who are at risk for severe illness include infants, elderly, organ-transplant recipients, and the immunocompromised.<ref name="Barbara2003" /> |
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=== Invasive nontyphoidal salmonella disease === |
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While in developed countries, nontyphoidal serovars present mostly as gastrointestinal disease; in sub-Saharan Africa, these serovars can create a major problem in bloodstream infections, and are the most commonly isolated bacteria from the blood of those presenting with fever. Bloodstream infections caused by nontyphoidal salmonellae in Africa were reported in 2012 to have a [[case fatality rate]] of 20–25%. Most cases of invasive nontyphoidal salmonella infection (iNTS) are caused by ''S. typhimurium'' or ''S. enteritidis''. A new form of ''Salmonella typhimurium'' (ST313) emerged in the southeast of the African continent 75 years ago, followed by a second wave which came out of central Africa 18 years later. This second wave of iNTS possibly originated in the Congo Basin, and early in the event picked up a gene that made it resistant to the antibiotic [[chloramphenicol]]. This created the need to use expensive antimicrobial drugs in areas of Africa that were very poor, making treatment difficult. The increased prevalence of iNTS in sub-Saharan Africa compared to other regions is thought to be due to the large proportion of the African population with some degree of immune suppression or impairment due to the burden of HIV, malaria, and malnutrition, especially in children. The genetic makeup of iNTS is evolving into a more typhoid-like bacterium, able to efficiently spread around the human body. Symptoms are reported to be diverse, including fever, [[hepatosplenomegaly]], and respiratory symptoms, often with an absence of gastrointestinal symptoms.<ref>{{cite journal|last=Feasey|first=Nicholas A.|author2=Gordon Dougan |author3=Robert A. Kingsley |author4=Robert S. Heyderman |author5=Melita A. Gordon |title=Invasive non-typhoidal salmonella disease: an emerging and neglected tropical disease in Africa|journal=The Lancet|year=2012|volume=379|pages=2489–2499|doi=10.1016/S0140-6736(11)61752-2}}</ref> |
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==Typhoidal ''Salmonella''== |
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{{See also|Typhoid fever|Paratyphoid fever}} |
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Typhoid fever is caused by ''Salmonella'' serotypes which are strictly adapted to humans or higher primates—these include [[Salmonella Typhi|''Salmonella ''Typhi]], Paratyphi A, Paratyphi B and Paratyphi C. In the systemic form of the disease, salmonellae pass through the lymphatic system of the intestine into the blood of the patients (typhoid form) and are carried to various organs (liver, spleen, kidneys) to form secondary foci (septic form). Endotoxins first act on the vascular and nervous apparatus, resulting in increased permeability and decreased tone of the vessels, upset of thermal regulation, and vomiting and diarrhoea. In severe forms of the disease, enough liquid and electrolytes are lost to upset the water-salt metabolism, decrease the circulating blood volume and arterial pressure, and cause [[hypovolemia|hypovolemic shock]]. [[septicaemia|Septic shock]] may also develop. Shock of mixed character (with signs of both hypovolemic and septic shock) is more common in severe [[salmonellosis]]. [[Oliguria]] and [[azotemia]] may develop in severe cases as a result of renal involvement due to [[hypoxia (medical)|hypoxia]] and [[Bacteremia|toxemia]]. |
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==Global monitoring== |
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In Germany, food poisoning infections must be reported.<ref>§ 6 and § 7 of the German law on infectious disease prevention, ''Infektionsschutzgesetz''</ref> From 1990 to 2005, the number of officially recorded cases decreased from about 200,000 to about 50,000 cases. In the United States, about 50,000 cases of ''Salmonella'' infection are reported each year.<ref>[http://www.cdc.gov/nczved/dfbmd/disease_listing/salmonellosis_gi.html#8 Centers for Disease Control and Prevention]</ref> A World Health Organization study estimated that 21,650,974 cases of typhoid fever occurred in 2000, 216,510 of which resulted in death, along with 5,412,744 cases of paratyphoid fever.<ref name=burden>{{cite journal|last1=Crump|first1=John A.|last2=Luby|first2=Stephen P.|last3=Mintz|first3=Eric D.|title=The global burden of typhoid fever.|journal=Bulletin of the World Health Organization|date=May 2004|volume=82|issue=5|pages=346–353|pmc=2622843|pmid=15298225}}</ref> |
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==Molecular mechanisms of infection== |
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Mechanisms of infection differ between typhoidal and nontyphoidal serovars, owing to their different targets in the body and the different symptoms that they cause. Both groups must enter by crossing the barrier created by the intestinal cell wall, but once they have passed this barrier, they use different strategies to cause infection. |
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Nontyphoidal serovars preferentially enter [[Microfold cell|M cells]] on the intestinal wall by bacterial-mediated [[endocytosis]], a process associated with intestinal inflammation and diarrhoea. They are also able to disrupt [[tight junction]]s between the cells of the intestinal wall, impairing the cells' ability to stop the flow of [[ions]], water, and immune cells into and out of the intestine. The combination of the inflammation caused by bacterial-mediated endocytosis and the disruption of tight junctions is thought to contribute significantly to the induction of diarrhoea.<ref name=Haraga>{{cite journal|last=Haraga|first=Andrea|author2=Maikke B. Ohlson |author3=Samuel I. Miller |title=Salmonellae interplay with host cells|journal=Nature Reviews Microbiology|year=2008|volume=6|pages=53–66|doi=10.1038/nrmicro1788}}</ref> |
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Salmonellae are also able to breach the intestinal barrier via [[phagocytosis]] and trafficking by [[CD18]]-positive immune cells, which may be a mechanism key to typhoidal ''Salmonella'' infection. This is thought to be a more stealthy way of passing the intestinal barrier, and may, therefore, contribute to the fact that lower numbers of typhoidal ''Salmonella'' are required for infection than nontyphoidal ''Salmonella''.<ref name=Haraga /> ''Salmonella'' cells are able to enter [[macrophage]]s via [[Macropinosome|macropinocytosis]].<ref>{{Cite journal |
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| last1 = Kerr | first1 = M. C. |
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| last2 = Wang | first2 = J. T. H. |
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| last3 = Castro | first3 = N. A. |
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| last4 = Hamilton | first4 = N. A. |
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| last5 = Town | first5 = L. |
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| last6 = Brown | first6 = D. L. |
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| last7 = Meunier | first7 = F. A. |
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| last8 = Brown | first8 = N. F. |
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| last9 = Stow | first9 = J. L. |
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| doi = 10.1038/emboj.2010.28 |
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| last10 = Teasdale | first10 = R. D. |
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| title = Inhibition of the PtdIns(5) kinase PIKfyve disrupts intracellular replication of Salmonella |
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| journal = The EMBO Journal |
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| volume = 29 |
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| issue = 8 |
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| pages = 1331–1347 |
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| year = 2010 |
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| pmid = 20300065 |
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| pmc =2868569 |
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}}</ref> Typhoidal serovars can use this to achieve dissemination throughout the body via the [[mononuclear phagocyte system]], a network of connective tissue that contains immune cells, and surrounds tissue associated with the immune system throughout the body.<ref name=Haraga /> |
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Much of the success of ''Salmonella'' in causing infection is attributed to two [[type III secretion system]]s which function at different times during an infection. One is required for the invasion of [[phagocytic cell|nonphagocytic cells]], colonization of the intestine, and induction of intestinal inflammatory responses and diarrhea. The other is important for survival in macrophages and establishment of systemic disease.<ref name=Haraga /> These systems contain many genes which must work co-operatively to achieve infection. |
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The AvrA toxin injected by the SPI1 type III secretion system of ''S.'' Typhimurium works to inhibit the [[innate immune system]] by virtue of its [[serine]]/[[threonine]] [[acetyltransferase]] activity, and requires binding to [[Eukaryotic cell|eukaryotic]] target cell [[phytic acid]] (IP6).<ref name="PMID20430892">{{cite journal |vauthors=Mittal R, Peak-Chew SY, Sade RS, Vallis Y, McMahon HT | title = The Acetyltransferase Activity of the Bacterial Toxin YopJ of Yersinia Is Activated by Eukaryotic Host Cell Inositol Hexakisphosphate | journal = J Biol Chem | volume = 285| issue = 26| pages = 19927–34| year = 2010 | pmid = 20430892 | pmc = 2888404| doi = 10.1074/jbc.M110.126581 | url = http://www.jbc.org/content/early/2010/04/29/jbc.M110.126581.long }}</ref> This leaves the host more susceptible to infection. |
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Salmonellosis is known to be able to cause [[back pain]] or [[spondylosis]]. It can manifest as five clinical patterns: gastrointestinal tract infection, enteric fever, bacteremia, local infection, and the chronic reservoir state. The initial symptoms are nonspecific fever, weakness, and myalgia among others. In the bacteremia state, it can spread to any parts of the body and this induces localized infection or it forms abscesses. The forms of localized ''Salmonella'' infections are arthritis, urinary tract infection, infection of the central nervous system, bone infection, soft tissue infection, etc.<ref name=salspond>{{cite journal | pmc = 3030045 | pmid=21286449 | doi=10.4097/kjae.2010.59.S.S233 | volume=59 Suppl | title=A case of back pain caused by Salmonella spondylitis -A case report- | year=2010 | journal=Korean J Anesthesiol | pages=S233–7 |vauthors=Choi YS, Cho WJ, Yun SH, Lee SY, Park SH, Park JC, Jang EH, Shin HY }}</ref> Infection may remain as the latent form for a long time, and when the function of [[Mononuclear phagocyte system|reticular endothelial cells]] is deteriorated, it may become activated and consequently, it may secondarily induce spreading infection in the bone several months or several years after acute salmonellosis.<ref name=salspond/> |
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==Resistance to oxidative burst== |
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A hallmark of ''Salmonella'' pathogenesis is the ability of the bacterium to survive and proliferate within [[phagocyte]]s. Phagocytes produce DNA damaging agents such as [[nitric oxide]] and oxygen [[Radical (chemistry)|radicals]] as a defense against pathogens. Thus, ''Salmonella'' must face attack by molecules that challenge genome integrity. Buchmeier'' et al.''<ref name=Buchmeier>{{cite journal |vauthors=Buchmeier NA, Lipps CJ, So MY, Heffron F |title=Recombination-deficient mutants of Salmonella typhimurium are avirulent and sensitive to the oxidative burst of macrophages |journal=Mol. Microbiol. |volume=7 |issue=6 |pages=933–6 |year=1993 |pmid=8387147 |doi= 10.1111/j.1365-2958.1993.tb01184.x|url=}}</ref> showed that mutants of ''Salmonella enterica'' lacking RecA or RecBC protein function are highly sensitive to oxidative compounds synthesized by macrophages, and furthermore these findings indicate that successful systemic infection by ''S. enterica'' requires RecA and RecBC mediated recombinational repair of DNA damage.<ref name=Buchmeier /><ref name="pmid11751841">{{cite journal |vauthors=Cano DA, Pucciarelli MG, García-del Portillo F, Casadesús J |title=Role of the RecBCD recombination pathway in Salmonella virulence |journal=J. Bacteriol. |volume=184 |issue=2 |pages=592–5 |year=2002 |pmid=11751841 |pmc=139588 |doi= 10.1128/jb.184.2.592-595.2002|url=}}</ref> |
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== Host adaptation == |
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''Salmonella enterica'', through some of its serovars such as Typhimurium and Enteriditis, shows signs of the ability to infect several different mammalian host species, while other serovars such as Typhi seem to be restricted to only a few hosts.<ref>{{cite journal | last1 = Thomson | first1 = Nicholas R. | last2 = Clayton | first2 = Debra J. | last3 = Windhorst | first3 = Daniel | display-authors = etal | year = 2008 | title = Comparative genome analysis of Salmonella Enteritidis PT4 and Salmonella Gallinarum 287/91 provides insights into evolutionary and host adaptation pathways | url = | journal = Genome Res. | volume = 18 | issue = | pages = 1624–1637 | doi = 10.1101/gr.077404.108 }}</ref> Some of the ways that ''Salmonella'' serovars have [[host adaptation|adapted]] to their hosts include loss of genetic material and mutation. In more complex mammalian species, [[immune system]]s, which include pathogen specific immune responses, target serovars of ''Salmonella'' through binding of antibodies to structures like flagella. Through the loss of the genetic material that codes for a flagellum to form, ''Salmonella'' can evade a host's [[immune system]].<ref>{{cite journal|authors=Pang, Stanley. Octavia, Sophie. Feng, Lu. Liu, Bin. Reeves, Peter R. Lan, Ruiting. Wang, Lei|title=Genomic diversity and adaptation of Salmonella enterica serovar Typhimurium from analysis of six genomes of different phage types|journal=BMC Genomics|year=2011|volume=12|page=425|doi=10.1186/1471-2164-12-425}}</ref> In the study by Kisela ''et al.'', more pathogenic serovars of ''S. enterica'' were found to have certain adhesins in common that have developed out of convergent evolution.<ref>{{cite journal | last1 = Kisiela | first1 = D. I. | last2 = Chattopadhyay | first2 = S. | last3 = Libby | first3 = S. J. | last4 = Karlinsey | first4 = J. E. | last5 = Fang | first5 = F. C. | display-authors = etal | year = 2012 | title = Evolution of Salmonella enterica Virulence via Point Mutations in the Fimbrial Adhesin | url = | journal = PLoS Pathog | volume = 8 | issue = 6| page = e1002733 | doi = 10.1371/journal.ppat.1002733 }}</ref> This means that, as these strains of ''Salmonella'' have been exposed to similar conditions such as immune systems, similar structures evolved separately to negate these similar, more advanced defenses in hosts. There are still many questions about the way that ''Salmonella'' has evolved into so many different types but it has been suggested that ''Salmonella'' evolved through several phases. As Baumler ''et al.'' have suggested, Salmonella most likely evolved through [[horizontal gene transfer]], formation of new serovars due to additional [[pathogenicity island]]s and through an approximation of its ancestry.<ref name="ReferenceA">{{cite journal | last1 = Bäumler | first1 = Andreas J. | last2 = Tsolis | first2 = Renée M. | last3 = Ficht | first3 = Thomas A. | last4 = Adams | first4 = L. Garry | year = 1998 | title = Evolution of Host Adaptation in ''Salmonella enterica'' | url = | journal = Infect. Immun | volume = 66 | issue = 10| pages = 4579–4587 | pmid =9746553|pmc=108564}}</ref> So, ''Salmonella'' could have evolved into its many different serovars through gaining genetic information from different pathogenic bacteria. The presence of several [[pathogenicity island]]s in the genome of different serovars has lent credence to this theory.<ref name="ReferenceA"/> |
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== Genetics == |
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In addition to its importance as a pathogen, ''Salmonella enterica'' serovar Typhimurium has been instrumental in the development of genetic tools that led to an understanding of fundamental bacterial physiology. These developments were enabled by the discovery of the first generalized transducing phage, P22,<ref>{{cite journal|vauthors=Zinder N, Lederberg J|year=1952|title=Genetic exchange in Salmonella|journal=J. Bacteriol.|volume=64|issue=5|pages=679–699|pmid=12999698|pmc=169409|url=https://profiles.nlm.nih.gov/ps/access/BBABFL.pdf}}</ref> in Typhimurium that allowed quick and easy genetic exchange that allowed fine structure genetic analysis. The large number of mutants led to a revision of genetic nomenclature for bacteria.<ref>{{cite journal|author1=Demerec, M. |author2=A. Adelberg|author3=A. J. Clark|author4=P. Hartman|year=1966|title=A proposal for a uniform nomenclature in bacterial genetics|journal=Genetics|volume=54|issue=1|pages=61–76|url=http://www.genetics.org/content/genetics/54/1/61.full.pdf|pmid=5961488|pmc=1211113}}</ref> Many of the uses of transposons as genetic tools, including transposon delivery, mutagenesis, construction of chromosome rearrangements, were also developed in Typhimurium. These genetic tools also led to a simple test for carcinogens, the Ames Test.<ref>{{cite journal|author1=Ames, B.|author2=J. McCann|author3=E. Yamasaki|year=1975|title=Methods for detecting carcinogens and mutagens with the Salmonella/mammalian-microsome mutagenicity test|journal=Mutat Res.|volume=31|issue=6|pages=347–364|pmid=768755|doi=10.1016/0165-1161(75)90046-1}}</ref> |
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== See also == |
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* [[Host-pathogen interface]] |
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* [[1984 Rajneeshee bioterror attack]] |
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* [[2008 United States salmonellosis outbreak]] |
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* [[Peanut Corporation of America#Georgia|2008–2009 peanut-borne salmonellosis]] |
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* [[Bismuth sulfite agar]] |
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* [[Food testing strips]] |
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* [[List of foodborne illness outbreaks]] |
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* [[Salmonellosis]] |
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* [[Wright County Egg]] |
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* [[Rappaport Vassiliadis soya peptone broth]] |
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* [[XLD agar]] |
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* [[American Public Health Association v. Butz]] |
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== References == |
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== External links == |
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{{Commons category|Salmonella}} |
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{{Wikispecies|Salmonella}} |
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* [http://www.fsis.usda.gov/wps/portal/fsis/topics/food-safety-education/get-answers/food-safety-fact-sheets/foodborne-illness-and-disease/salmonella-questions-and-answers/CT_Index Background on Salmonella] from the [http://www.fsis.usda.gov/ Food Safety and Inspection Service] of the [http://www.usda.gov/wps/portal/usdahome United States Department of Agriculture] |
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* [http://patricbrc.org/portal/portal/patric/Taxon?cType=taxon&cId=590 Salmonella] genomes and related information at [http://patricbrc.org/ PATRIC], a Bioinformatics Resource Center funded by [https://www.niaid.nih.gov/ NIAID] |
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* [http://www.unitedsanitizing.com/index.php/technical/frequently-asked-questions/ Questions and Answers about commercial and institutional sanitizing methods] |
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* [http://www.healthline.com/channel/salmonella-food-poisoning_symptoms Symptoms of Salmonella Poisoning] |
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* [http://epi.ufl.edu/food/ ''Salmonella'' as an emerging pathogen] from [[Institute of Food and Agricultural Sciences|IFAS]] |
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* [http://www.bacterio.cict.fr/salmonellanom.html Notes on ''Salmonella'' nomenclature] |
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* [http://www.tgw1916.net/movies.html Salmonella motility] video |
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* [http://wildlifedisease.nbii.gov/diseasehome.jsp?disease=Avian%20Salmonella&pagemode=submit Avian Salmonella] |
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* [http://www.merckmanuals.com/vet/digestive_system/salmonellosis/overview_of_salmonellosis.html#v3261669 Overview of Salmonellosis] — The Merck Veterinary Manual |
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{{Bacteria classification}} |
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{{Chicken}} |
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{{Consumer Food Safety}} |
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[[Category:Salmonella| ]] |
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[[Category:Enterobacteria]] |
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[[Category:Gram-negative bacteria]] |
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[[Category:Pathogenic bacteria]] |
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[[Category:Zoonoses]] |
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[[Category:Rodent-carried diseases]] |
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[[Category:Bacteria genera]] |
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