Salmonella
Salmonella as disease-causing agent
Salmonella infections are zoonotic; they can be transmitted by humans to animals and vice versa. Infection via food is also possible. A distinction is made between enteritis salmonella and typhoid/paratyphoid salmonella, whereby the latter because of a special virulence factor and a capsule protein (virulence antigen) can cause serious illness, such as Salmonella enterica subsp. enterica Serovar Typhi, or Salmonella typhi). Salmonella typhi is adapted to humans and does not occur in animals.
Enteritis Salmonella (e.g., Salmonella enterica subsp. enterica serovar Enteritidis) can cause diarrhea, which usually does not require antibiotic treatment. However, people at risk such as infants, small children, the elderly, Salmonella can become very serious, leading to complications. If this is not treated HIV patients and those with suppressed immunity can become seriously ill. Children with sickle cell anemia who are infected with salmonella may develop osteomyelitis.
In Germany, Salmonella infections must be reported ( 6 and 7 of the German law on infectious disease prevention, Infektionsschutzgesetz). Between 1990 and 2005 the number of officially recorded cases decreased from approximately 200,000 cases to approximately 50,000. It is estimated that every fifth person in Germany is a carrier of Salmonella. In the USA, there are approximately 40,000 cases of Salmonella infection reported each year. According to the World Health Organization, over 16 million people worldwide are infected with typhoid fever each year, with 500,000 to 600,000 of these cases proving to be fatal.
Salmonella can survive for weeks outside a living body. They have been found in dried excrement after over 2.5 years.
Ultraviolet radiation and heat accelerate their demise; they perish after being heated to 55 C (131 F) for one hour, or to 60 C (140 F) for half an hour.[citation needed]
To protect against Salmonella infection, it is recommended that food be heated for at least ten minutes at 75 C (167 F) so that the center of the food reaches this temperature.
Salmonella is not destroyed by freezing.
History
The genus Salmonella was named after Daniel Elmer Salmon, an American veterinary pathologist. While Theobald Smith was the actual discoverer of the type bacterium (Salmonella enterica var. Choleraesuis) in 1885, Dr. Salmon was the administrator of the USDA research program, and thus the organism was named after him. Smith and Salmon had been searching for the cause of common hog cholera and proposed this organism as the causal agent. Later research, however, would show that this organism (now known as Salmonella enterica) rarely causes enteric symptoms in pigs, and was thus not the agent they were seeking (which was eventually shown to be a virus). However, related bacteria in the genus Salmonella were eventually shown to cause other important infectious diseases.
Salmonella nomenclature
Salmonella nomenclature is complicated. Initially each Salmonella species was named according to clinical considerations, e.g., Salmonella typhi-murium (mouse typhoid fever), S. cholerae-suis (hog cholera). After it was recognized that host specificity did not exist for many species, new strains (or serovar, short for serological variants) 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, S. enterica, and the serovar were classified into six groups, two of which are medically relevant. But as this now formalized nomenclature is not in harmony with the traditional usage familiar to specialists in microbiology and infectologists, the traditional nomenclature is common. Currently, there are two recognized species: S. enterica and S. bongori, with six main subspecies: enterica (I), salamae (II), arizonae (IIIa), diarizonae (IIIb), houtenae (IV), and indica (VI). Historically, serotype (V) was bongori, which is now considered its own species.
Genetics
Serovar Typhimurium has considerable diversity and may be very old. The majority of the isolates belong to a single clonal complex. Isolates are divided into phage types, but some phage types do not have a single origin as determined using mutational changes. Phage type DT104 is heterogeneous and represented in multiple sequence types, with its multidrug-resistant variant being the most successful and causing epidemics in many parts of the world.
Serovar Typhi is relatively young compared to Typhimurium, and probably originated approximately 30,000-50,000 years ago.
Sources of infection
Unclean food, particularly in institutional kitchens and restaurants,
Excretions from either sick or infected but apparently clinically healthy people and animals (especially endangered are caregivers and animals),
Polluted surface water and standing water (such as in shower hoses or unused water dispensers),
Unhygienically thawed fowl (the meltwater contains many bacteria),
An association with reptiles (pet tortoises and snakes) is well described.
Salmonella bacteria can survive several weeks in a dry environment and several months in water; thus, they are frequently found in polluted water, contamination from the excrement of carrier animals being particularly important. Aquatic vertebrates, notably birds and reptiles, are important vectors of salmonella. Poultry, cattle, and sheep frequently being agents of contamination, salmonella can be found in food, particularly meats and raw eggs.
Deaths
About 142,000 Americans are infected each year with Salmonella enteritidis from chicken eggs and about 30 die. The shell of the egg or its interior may be contaminated.
Medically relevant representatives
S. enterica ssp. arizonae, in cold-blooded animals, poultry, mammals
S. choleraesuis (Bacillus paratyphoid B and C), intestinal commensalists in pigs, pathogenic if resistance is weak; humans can be infected by ingesting sick animals; the bacteria causes septicemic Salmonellosis in swine.
S. enteritidis, in the intestines of cattle, rodents, ducks (and their eggs) and humans; causes calf paratyphoid fever and acute gastroenteritis in humans
S. paratyphi
S. paratyphi A, solely a human pathogen, causes paratyphoid A, transmission by contact and infected food or water
S. paratyphi B, in central Europe usually a human pathogen, causes paratyphoid B; transmission by contact and infected food, water or fly excrement
S. typhi, occurs in temperate and subtropical zones, the human pathogen of typhus abdominalis; transmission by contact and infected food, water or fly excrement; 35 % of all persons falling ill remain permanent carriers of the pathogen
S. typhimurium, causes a wide range of infections in birds and mammals ranging from self limiting gastroenteritis to severe systemic paratyphoid diseases; conveyed by contaminated foodstuffs; causes Salmonella enteritis (“food poisoning”) in humans
S. dublin, one of the pathogens causing cattle salmonellosis
S. typhisuis, one of the pathogens causing hog salmonellosis
See also
Salmonellosis
Food Testing Strips
XLD agar
Bismuth sulfite agar
List of foodborne illness outbreaks
20082009 peanut-borne salmonella outbreak
2008 United States salmonellosis outbreak
1984 Rajneeshee bioterror attack
References
^ Giannella RA (1996). “Salmonella”. in Baron S et al (eds.). Baron’s Medical Microbiology (4th ed.). Univ of Texas Medical Branch. ISBN 0-9631172-1-1. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mmed.section.1929.
^ Ryan KJ, Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. pp. 3628. ISBN 0-8385-8529-9.
^ Centers for Disease Control and Prevention
^ “FDA/CFSAN – Food Safety A to Z Reference Guide – Salmonella”. FDA – Center for Food Safety and Applied Nutrition. 2008-07-03. http://www.cfsan.fda.gov/~dms/a2z-s.html. Retrieved 2009-02-14.
^ http://www.cgmh.org.tw/chldhos/intr/c4a00/academy/bugs/salchole.html S. cholerasuis pathology. Accessed April 3., 2009
^ F. Kauffmann: Die Bakteriologie der Salmonella-Gruppe. Munksgaard, Kopenhagen, 1941
^ L. Le Minor, M. Y. Popoff: Request for an Opinion. Designation of Salmonella enterica. sp. nov., nom. rev., as the type and only species of the genus Salmonella. In: Int. J. Syst. Bacteriol., Bd. 37, 1987, S. 465468
^ M. W. Reeves, G. M. Evins, A. A. Heiba, B. D. Plikaytis, J. J. Farmer III: 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. In: J. Clin. Microbiol. Bd. 27, 1989, S. 313320. PMID 2915026
^ Judicial Commission of the International Committee on Systematics of Prokaryotes: 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. In: Int. J. Syst. Evol. Microbiol. Bd. 55, 2005, S. 519520. PMID 15653929
^ B. J. Tindall, P. A. Grimont, G. M. Garrity, J. P. Euzeby: Nomenclature and taxonomy of the genus Salmonella . In: Int. J. Syst. Evol. Microbiol. Bd. 55, 2005, S. 521524. PMID 15653930
^ Janda JM, Abbott SL (2006). “The Enterobacteria”, ASM Press.
^ “Ongoing investigation into reptile associated salmonella infections”. Health Protection Report 3 (14). 9 April 2009. http://www.hpa.org.uk/hpr/archives/2009/news1409.htm#reptiles. Retrieved 12 April 2009.
^ “Administration Urged to Boost Food Safety Efforts”. Washington Post. 2009. http://www.washingtonpost.com/wp-dyn/content/article/2009/07/07/AR2009070702343.html?hpid=topnews. Retrieved 2009-07-07. “Among them is a final rule, issued by the FDA, to reduce the contamination in eggs. About 142,000 Americans are infected each year with Salmonella enteritidis from eggs, the result of an infected hen passing along the bacterium. About 30 die.”
External links
Wikimedia Commons has media related to: Salmonella
Wikispecies has information related to: Salmonella
Background on Salmonella from the Food Safety and Inspection Service of the United States Department of Agriculture
Questions and Answers about sanitizing methods
Symptoms of Salmonella Poisoning
Salmonella as an emerging pathogen from IFAS
Notes on Salmonella nomenclature
Genome information is available at the NIAID PathoSystems Resource Integration Center (PATRIC)
Salmonella motility video
Avian Salmonella
v d e
Prokaryotes: Bacteria classification
Domain: Archaea Bacteria Eukaryota
G-/
OM
Terra-/Glidobacteria
Eobacteria (Chloroflexi, Deinococcus-Thermus) Cyanobacteria
Gracilicutes
Proteobacteria
Alpha Beta Gamma/Enterobacteriaceae (Salmonella, Vibrio, Shigella) Delta Epsilon (Campylobacter) / Aquificae (Aquifex)
Planctobacteria
Chlamydiae/Verrucomicrobia Planctomycetes
Sphingobacteria
Bacteroidetes/Chlorobi Fibrobacteres
Other
Spirochaetes
Eurybacteria
Fusobacteria Thermotogae
Other/ungrouped
Acidobacteria Chrysiogenetes Deferribacteres Gemmatimonadetes Nitrospirae Synergistetes Thermodesulfobacteria Dictyoglomi
G+/
no OM
Actinobacteria
Actinobacteridae
Actinomycetales
Actinomycineae: Actinomycetaceae (Actinomyces, Mobiluncus)
Corynebacterineae: Mycobacteriaceae Nocardiaceae Corynebacteriaceae
Frankineae: Frankiaceae
Micrococcineae: Brevibacteriaceae
Bifidobacteriales
Bifidobacteriaceae (Bifidobacterium, Falcivibrio, Gardnerella)
Other subclasses
Acidimicrobidae Coriobacteridae Rubrobacteridae Sphaerobacteridae
Firmicutes
Bacilli
Bacillales: Bacillaceae (Bacillus) Listeriaceae (Listeria) Staphylococcaceae (Staphylococcus, Gemella, Jeotgalicoccus)
Lactobacillales: Enterococcaceae (Enterococcus) Lactobacillaceae (Lactobacillus, Pediococcus) Leuconostocaceae (Leuconostoc) Streptococcaceae (Lactococcus, Streptococcus)
Clostridia
Clostridiales (Clostridium, Peptostreptococcus, Selenomonas) Halanaerobiales Thermoanaerobacterales
Tenericutes/
Mollicutes
Mycoplasmatales (Mycoplasma, Ureaplasma) Entomoplasmatales (Spiroplasma) Anaeroplasmatales (Erysipelothrix) Acholeplasmatales (Acholeplasma) Haloplasmatales (Haloplasma)
note: not all classifications are universally accepted
v d e
Consumer Food Safety
Adulterants/Food contaminants
Formaldehyde Melamine 3-MCPD Cyanide Lead poisoning Mercury in fish Sudan red dye Aldicarb
Toxins/Poisons
Mycotoxins Shellfish poisoning Arsenic contamination of groundwater Aflatoxin Benzene in soft drinks Bisphenol A
Microorganisms
Campylobacter jejuni Escherichia coli O157:H7 Salmonella Listeria Botulism Clostridium perfringens Hepatitis A Hepatitis E Rotavirus Norovirus
Pesticides Overuse/Residues
Lindane DDT, Malathion, Chlorpyrifos, Methamidophos
Preservatives
Benzoic acid sodium benzoate EDTA
Sweeteners
Cyclamate Aspartame controversy Saccharin Sucralose acesulfame potassium high fructose corn syrup sorbitol
Food Scares
ICA meat repackaging controversy Bradford sweets poisoning Minamata disease Chilean grape scare 2005 Indonesia food scare 2008 Chinese milk scandal 2007 Vietnam food scare 2008 Canadian listeriosis outbreak 2008 United States salmonellosis outbreak 2006 North American E. coli outbreak Irish pork crisis of 2008 Toxic oil syndrome List of foodborne illness outbreaks List of food contamination incidents
Regulatory/Watchdog
International Food Safety Network Food and Drug Administration E number Acceptable daily intake Food Standards Agency Quality Assurance International Food Safety Act 1990 Pure Food and Drug Act European Food Safety Authority List of food safety organisations Food law Early history of food regulation in the United States Food labeling regulations
Food Processing
Polycyclic aromatic hydrocarbon Food irradiation Nitrosamines Trans fat Acrylamide Shortening Hydrolyzed vegetable protein Modified starch 4-Hydroxynonenal Heterocyclic amines Creutzfeldtakob disease
Misc
Foodborne illness Food Preservation Food safety in the People’s Republic of China Curing (food preservation) Food quality Food marketing Genetically modified food Food safety (science) Food politics
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