Salmonella enterica

In Salmonella enterica PRPP is a central metabolite that serves as a forerunner in the biosynthesis of nucleotides (purine, pyrimidine, and pyridine) and amino acids (tryptophan and histidine) in a highly branched series of metabolic pathways.

From: Brenner'south Encyclopedia of Genetics (2d Edition) , 2013

Typhoid Fever, Paratyphoid Fever, and Typhoidal Fevers

John E. Bennett MD , in Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases , 2020

Nomenclature and Classification of TyphoidalSalmonella enterica

Salmonella Typhi andSalmonella Paratyphi A, B, and C are gram-negative bacilli that belong to the speciesSouthward. enterica subspeciesenterica. AllS. enterica are categorized serologically by the Centers for Disease Control and Prevention (CDC) according to a modified Kauffman and White classification scheme, assigned based both on the O (the O polysaccharide) and H (flagellar) antigens. 14,xv Although assigning a serogroup based on O antigen agglutination tests is a common procedure in many clinical microbiology laboratories, the approach has limited clinical utility. Complete serotyping based on both the O and H antigen is virtually commonly performed in reference laboratories. In addition to serogrouping and serotyping, standard microbiologic growth and biochemical parameters are also routinely used in the clinical laboratory for the presumptive identification ofS. enterica. Serologic and selected biochemical characteristics that are used in the identification ofSalmonella Typhi andSalmonella Paratyphi A, B, and C in microbiology laboratories are summarized inTable 100.ane.

Typhoid and Paratyphoid (Enteric) Fever

Jason B Harris , W Abdullah Brooks , in Hunter's Tropical Medicine and Emerging Infectious Affliction (Ninth Edition), 2013

Salmonella enterica subsp. enterica includes over 1400 serotypes. Although the full proper name of the cause of typhoid fever is Salmonella enterica subsp. enterica serotype Typhi, information technology is normally only shortened to: S. Typhi. While serogroup designation is performed routinely in many laboratories, the test lacks clinical utility. Complete serotype identification is frequently performed in a reference laboratory; however, S. Typhi and Paratyphi A tin can as well exist identified past biochemical tests in a routine microbiology laboratory. Identification of South. Typhi and Paratyphi A are reviewed in particular in the World Health Arrangement's "The diagnosis, treatment and prevention of typhoid fever" [22].

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The Microbiome in Health and Affliction

Matthew Silbergleit , ... Ikuko Kato , in Progress in Molecular Biological science and Translational Science, 2020

8.ane Background of Salmonella enterica infection in humans

Salmonella enterica is a Gram-negative, facultative anaerobe, not a symbiotic commensal, but an intracellular pathogen to both humans and animals. Salmonella infection poses a major public health concern worldwide equally foodborne illness. 250 At that place has been besides a concern that long-standing Salmonella infection may increase the risk of colorectal cancer in humans equally increased take a chance of colorectal tumor has been reported in several populations worldwide. 251,252 The Salmonella genome contains a remarkably big number (up to 23) of pathogenicity islands (SPI), 253,254 synthesizing over threescore effectors. 255 We describe here Avirulence poly peptide A (AvrA), one of the bacterial type three secretion arrangement effectors as there take been recent significant findings to support its oncogenicity.

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Biological science and Diseases of Ruminants (Sheep, Goats, and Cattle)

Wendy J. Underwood DVM, MS, DACVIM , ... Adam Schoell DVM, DACLAM , in Laboratory Creature Medicine (3rd Edition), 2015

Etiology

Salmonella enterica is a motile, aerobic to facultatively anaerobic, nonspore-forming, gram-negative bacillus and is a common inhabitant of the gastrointestinal tract of ruminants. The genus Salmonella contains two species, S. bongori which infects mainly poikilotherms and rarely, humans, and S. enterica which includes approximately 2500 serovars and are a major cause of food-borne illness in humans. Salmonella are properly designated using their serovar (which was ofttimes formerly a species name), so, for example, S. enterica subsp. enterica serovar Typhimurium (aka S. Typhimurium) and serovar Enteritidis (S. Enteritidis). The organism is associated with enteric affliction and abortions. The most common serovars in animals (as reported to the CDC) are S. Typhimurium, S. Newport, South. Agona, S. Heidelberg; S. Dublin and Due south. Abortusovis have been implicated with bovine and ovine abortions (Center for Food Security and Public Prophylactic, 2005).

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Salmonella

John A. Crump , John Wain , in International Encyclopedia of Public Health (2d Edition), 2017

Abstract

Salmonella enterica remains a major crusade of morbidity and mortality worldwide. In industrialized countries, nontyphoidal serovars of South. enterica are important causes of diarrhea. In depression-resource settings, particularly in sub-Saharan African countries, nontyphoidal Salmonella are also leading causes of bloodstream infection. Typhoidal serovars of S. enterica cause enteric fever which is common in areas with unsafe h2o and poor sanitation. Post-obit identification to the species level, subsequent identification is by serogrouping and serotyping, with over 2400 serovars identified. Methods for discrimination within serovars of clinical and epidemiological importance include established tests such as phage typing and pulsed field gel electrophoresis. However, these are rapidly existence replaced with DNA sequencing, either sample sequencing such as multilocus sequence typing or increasingly with whole genome sequencing (WGS). Large databases containing tens of thousands of whole genome sequences now be in national reference laboratories in some high resource settings assuasive outbreak detection using WGS. Antimicrobial drug resistance is increasing in prevalence worldwide, with considerable implications for treatment of individuals infected with invasive strains and for public health. Control of Salmonella may be by vaccine, equally for typhoid in humans and Salmonella Enteritidis infection in poultry, and by nonvaccine measures such as improvements in h2o, sanitation, and food safety.

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Amino Acids, Peptides and Proteins

Holger Barth , Bradley G. Stiles , in Comprehensive Natural Products 2, 2010

5.06.2.one Salmonella enterica SpvB

Salmonella enterica is a Gram-negative, food-borne pathogen that causes human diseases ranging from mild gastroenteritis to severe systemic infections. For an infection to occur, the intracellular growth of Salmonella in macrophages is crucial. The bacteria are located in a special membrane compartment, the so-called Salmonella-containing vacuole (SCV). 21 Post-obit replication, Salmonella escapes from the SCV and induces prison cell expiry among infected macrophages. An actin-ADP-ribosylating virulence factor (SpvB – Salmonella plasmid virulence B) is highly essential for intracellular growth, and thus virulence, of Due south. enterica. fifteen SpvB is not an exotoxin and therefore requires the presence of Salmonella for its transport into the cytosol of mammalian cells. Most probably, the 65   kDa SpvB protein is direct secreted into the cytosol from intracellular growing bacteria through a type-III-secretion mechanism (run across Figure three ). Type-III-secretion implies the formation of a bacterial poly peptide needle (injectisome) that extends from the bacterium and through the host-cell membrane into the cytosol. The Northward-terminal domain of Southward. enterica SpvB shares homology with a secretory protein (TcaC) from Photorhabdus luminescens, an insect pathogen. 15

Figure 3. The SpvB virulence factor is of import for intracellular growth of Salmonella enterica. (a) An ADP-ribosyltransferase, SpvB, is crucial for the intracellular growth of Salmonella enterica in macrophages and host infection. Strains without SpvB are less virulent. During infection, the bacterium replicates inside macrophages in a special membrane compartment, the Salmonella-containing vacuole (SCV). Virtually probably, SpvB is delivered directly into the cytosol from engulfed Salmonella through type-Iii-secretion. One time in the host cell cytosol, SpvB mono-ADP-ribosylates G-actin at Arg177, which then leads to depolymerization of actin filaments. (b) The ADP-ribosyltransferase SpvB. An N-terminal domain (amino acids ane–365) shares sequence homology with a secreted, insecticidal poly peptide (TcaC) from Photorhabdus luminescens. The seven proline residues (Pro-7) that connect the N- with the C-terminal domains of SpvB might be involved in protein translocation. The C-terminal domain (C/SpvB) harbors the catalytic site for ADP-ribosyltransferase activity. The highly conserved residues that compose the catalytic site are depicted. In particular, Glu536 and Glu538 residues are characteristic of arginine-specific mono-ADP-ribosyltransferases from leaner.

The C-terminal domain of SpvB (C/SpvB) harbors an ADP-ribosyltransferase domain and shares sequence similarity with other actin-ADP-ribosylating toxins. 22 C/SpvB contains the highly conserved, essential residues Glu536 and Glu538 fifteen (see Figure 3 ). This motif is characteristic for the arginine-specific bacterial mono-ADP-ribosyltransferases. Recently, a crystal structure for the ADP-ribosyltransferase domain of SpvB (amino acids 390–591) was solved, revealing hitting similarities to previously characterized ADP-ribosyltransferases. 14 Between the Due north- and C-last domains, there are 7 proline residues which might be involved in translocating the protein into the cytosol. Recently, the molecular way of activity for SpvB was characterized and involves ADP-ribosylation of G-actin at Arg177. 14,23,24 As a event, the F-actin become depolymerized which adversely affects the cytoskeleton and many cell-essential functions critical for life.

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History, Science and Methods

S. Ethelberg , ... M.H. Josefsen , in Encyclopedia of Food Safety, 2014

Morphology, Metabolism, and Growth

Salmonella enterica is a Gram-negative rod-shaped enterobacterium. The size of the rods ranges from 0.7–1.5   μm to ii.2–5.0   μm; Salmonella produces colonies of approximately 2–iv   mm in diameter. They have peritrichous flagella, although they are sometimes nonmotile. They are facultative anaerobic chemoorganotrophs. They are oxidase negative and catalase positive. They are generally: able to reduce nitrate to nitrite, able to grow on citrate every bit sole carbon source, capable of producing acid and gas from glucose, able to produce hydrogen sulfide on triple sugar iron and decarboxylate lysine and ornithine, and able to hydrolyze indole and urea.

Salmonellae are adapted to life in the animal gut and their optimal growth temperature is 37   °C. Some serotypes may be found in a number of dissimilar hosts whereas others have adapted to specific hosts. Serotypes may be said to exist 'host adjusted' if they are prevalent in one item host, and too able to colonize and perhaps cause affliction in other hosts. An example of this would be South. Dublin which infects cattle, but rarely humans; however, when doing so causes systemic infections at a very loftier rate (resulting in instance fatality rates of twenty–30%). S. Kentucky, common in poultry but less common in humans, is another example of a host-adapted serotype. Some serotypes are host specific, i.e., are able to grow in one host merely. A special example hereof is S. Typhi and South. Paratyphi that are constitute in humans only, where they cause enteric fever (and are thus not zoonotic salmonella types). In general, the mechanisms underlying host adjustability are poorly understood.

Salmonella may survive for long periods outside of the torso and may persist for long periods in, for instance, food production environments. Salmonella has rarely given rise to outbreaks via drinking water, simply may survive and multiply in foods, and storage of foods at room temperature for prolonged periods before consumption has been institute to be a gamble factor for outbreaks to occur on multiple occasions. Salmonella will not ordinarily grow at refrigerator temperatures; the temperature range of growth is 7–45   °C. Salmonella normally survives freezing. Optimum pH for growth is 6.5–7.5, but salmonellae can proliferate in the range of pH four.v–9.5. Growth of Salmonella has not been reported in foods with an aw of less than 0.93. Even so, leaner may survive very well in dry foods.

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History, Scientific discipline and Methods

Southward.P. Luby , in Encyclopedia of Nutrient Safety, 2014

Characteristics

Salmonella enterica are rod-shaped, facultative anaerobic Gram-negative leaner. Virtually S. enterica infect birds and domestic animals and zoonoses are an important pathway for human infection, just Salmonella Typhi and Paratyphi A have a much more than restricted host range. Although it is often stated that Salmonella Typhi only infect humans, it can also infect other primates closely related to humans, though it is not known how frequently this occurs in nature, nor whether such infections contribute to the propagation and survival of the organism. Salmonella Paratyphi B and C infect other animals.

Salmonella Paratyphi A, B, and C are quite dissimilar organisms. Although Salmonella Paratyphi A is in a different serogroup than Salmonella Typhi, because of a modest difference in lipopolysaccharide sugars, they are genetically very closely related. The restricted host range of Salmonella Typhi apparently results from the inactivation of over 200 pseudogenes (v% of its genome). Over half of the pseudogenes are inactivated by a single frame shift or stop codon. Salmonella Paratyphi A also has numerous inactivated pseudogenes comprising 4% of its genome. The Salmonella Paratyphi A pseudogenes are less diverse than those in Salmonella Typhi suggesting that Salmonella Paratyphi A is a younger clone. Salmonella Paratyphi B is a remarkably various serovar; merely some of these strains cause enteric fever. Other strains of Salmonella Paratyphi B, previously identified as Due south. enterica serotype Java now referred to equally biotype Java, commonly infect poultry and do non typically cause typhoid fever. The Salmonella Paratyphi C genome is more closely related to other S. enterica serovars than information technology is to Salmonella Typhi.

Homo infection with most S. enterica produces an exudative intestinal inflammation that causes diarrhea, which increases the shedding of the pathogen so it's opportunity for ongoing transmission and survival. By contrast, in human typhoidal Salmonella infection, diarrhea is uncommon, occurring in only xxx% of cases severe enough to be hospitalized and in <ten% of outpatients with milder illness. The typhoidal Salmonellas are invasive, crusade systematic infection, and i–4% of all Salmonella Typhi and Paratyphi A infections event in long-term colonization of the hepatobiliary tract, specially the gallbladder. Typhoid/paratyphoid carriers can excrete the organism for decades, which provides opportunities for ongoing transmission of these host-restricted pathogens. Indeed, the evolutionary survival benefit of invasion and systematic infection for Salmonella Typhi and Paratyphi A probable results from the increased opportunity for hepatobiliary colonization and chronic carriage.

Like other Due south. enterica, when the typhoidal Salmonellas are inoculated at favorable temperatures into a nutrient-rich environment, such as cutting fruit or dairy products, they reproduce exponentially.

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The problem of resistance

Olivier Denis , ... Marc J. Struelens , in Antibody and Chemotherapy (Ninth Edition), 2010

Salmonella

Salmonella enterica serotype Typhi has developed multiple resistance to outset-line antibiotics in many developing countries. In the 1970s, strains with plasmid-mediated resistance to ampicillin and chloramphenicol caused epidemics in Latin America. In the 1980s, strains with plasmid-mediated resistance to ampicillin, chloramphenicol and co-trimoxazole emerged in Southward East Asia and have since become widespread in Asia and Latin America, where rates of 30–70% multiresistant Salmonella Typhi were reported in the 1990s. Fluoroquinolone resistance is now emerging in MDR strains and has been associated with recent outbreaks of typhoid fever in Tajikistan, Vietnam and the Indian subcontinent. The proportion of Salmonella Typhi with depression-level resistance to ciprofloxacin showed a rapid increase to more than xx% in 1999 in the UK, and was mostly seen in travelers returning from the Indian subcontinent. 89

In the 1990s, multiple resistance too rose apace in non-typhoidal salmonellae in Europe and in the U.s.. There is conclusive bear witness that antibiotics used in brute husbandry have contributed to antibiotic resistance in human isolates. In the Great britain and other European countries, the incidence of human infections with multiresistant Salmonella ser. Typhimurium DT104 resistant to ampicillin, chloramphenicol, streptomycin, co-trimoxazole and tetracycline increased markedly during the menstruum 1990–1996, at a fourth dimension when penicillin and tetracycline were commonly used in cattle feed. In Denmark, an outbreak of food-borne salmonellosis caused by a multidrug and low-level fluoroquinolone-resistant Salmonella ser. Typhimurium was traced to an infected swine herd. This strain was nalidixic acid resistant and showed increased ciprofloxacin MIC (0.06–0.12 mg/Fifty). Although this level of susceptibility is categorized equally sensitive by current breakpoints, patients treated with fluoroquinolones showed poor clinical response. 90

Before long subsequently the introduction of enrofloxacin for veterinary use in the UK in 1993, homo Salmonella isolates with decreased susceptibility to ciprofloxacin increased ten-fold from 1994 to 1997. In 1999, before long after the introduction of codes of practiced practice for the safety use of fluoroquinolones in animal husbandry in the UK, there was a 75% reject in isolations of multiresistant Salmonella ser. Typhimurium DT104 from clinical specimens, which may indicate a favorable impact of more prudent antibiotic use. 91 The extended-spectrum β-lactamases take appeared in some Salmonella strains, possibly as a result of plasmid transfer from commensal enterobacteria in the human gut. ESBL-producing salmonellae caused epidemics in Greece and spread to other European countries in the 1990s. 92 The commencement case of infection by ceftriaxone-resistant Salmonella reported in the USA was linked to contact with infected cattle treated with cephalosporins on a Nebraska farm. 93

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Metal Sensing in Salmonella

Deenah Osman , Jennifer Southward. Cavet , in Advances in Microbial Physiology, 2011

1.1 Overview of Salmonella Affliction Progression

Salmonella enterica serovars represent a major public health brunt worldwide, causing over 1 billion human infections annually and existence responsible for pregnant morbidity and mortality (Coburn et al., 2007). The disease manifestation varies depending upon the infectious S. enterica serovar and the host susceptibility, with localized gastrointestinal illness (nontyphoidal) and systemic enteric fever (typhoidal) existence the most mutual syndromes in humans. The emergence of multidrug resistant strains limits the possibilities of effective treatment and new antimicrobial targets are required. S. enterica serovar Typhimurium (S. enterica sv. Typhimurium) is broadly host adapted and a major cause of nutrient-associated nontyphoidal gastrointestinal disease, with asymptomatic carriage in farm animals presenting a mutual reservoir for manual to humans. The majority of these infections are cocky-limited with the leaner remaining localized to the intestine, although in a proportion of cases, most notably of the immunocompromised, infants and the elderly, the infection tin get systemic and life threatening. Furthermore, S. enterica sv. Typhimurium infections in mice cause a severe systemic disease which shares many of the features of human typhoid fever, caused by the human host restricted serovar Typhi, and thus have been extensively studied every bit a model for systemic salmonellosis.

During the infection procedure, S. enterica sv. Typhimurium encounters various microenvironments imposing different environmental stresses. Post-obit oral ingestion, gastric survival of S. enterica sv. Typhimurium is required before passage to the minor intestine (Haraga et al., 2008). This presents the initial site of infection and colonization proceeds by penetration of the abdominal mucosa (McGhie et al., 2009). During localized gastroenteritis, a prominent immune response is induced culminating in tissue injury, prison cell shedding and onset of diarrhoeal symptoms. In contrast, only a weak inflammatory response is associated with systemic infection outcomes. Bacteria are engulfed by resident macrophages and dendritic cells of the submucosa and enter the reticuloendothelial system (Haraga et al., 2008). The infection proceeds by entry of bacteria-containing phagocytes or free extracellular bacteria into the bloodstream directly, or via the mesenteric lymph node if associated with Thou cell invasion. This dissemination results in bacterial passage to extraintestinal sites, primarily the liver and spleen, which form the main foci of systemic infection (Haraga et al., 2008). Hither, S. enterica sv. Typhimurium has been associated with various cell types, but is thought to primarily reside within macrophages in a membrane-bound compartment known as the Salmonella-containing vacuole. Persistent infection may also involve colonization of the gall float. Crucial to the virulence of Due south. enterica sv. Typhimurium during systemic disease is the ability to survive within macrophage phagosomes, despite the antimicrobial mechanisms in this compartment (Fields et al., 1986). These include reactive oxygen species resulting from the action of the respiratory flare-up (NADPH) oxidase, the production of nitric oxide catalysed by inducible nitric oxide synthase, a reduction in pH due to the vacuolar ATPase, fusion with lysosomes delivering hydrolases and cationic antimicrobial peptides, besides as fluctuating metallic levels (Segal and Shatwell, 1997; Mastroeni et al., 2000; Vazquez-Torres et al., 2000; Blackwell et al., 2001; White et al., 2005; Techau et al., 2007).

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