User:YoungGA23/Salmonella enterica subsp. enterica

(Asa) Epidemiology:

Main article: Salmonellosis

The World Health Organization characterizes salmonellosis as a foodborne disease whose symptoms include diarrhea, fever, nausea, vomiting, and in severe cases death. Salmonellosis has been assessed to primarily occur in human hosts due to bacterial colonization of the intestinal track after the consumption of contaminated food or water, but it is also known to spread from person-to-person to via the fecal-oral-route. To reduce the risk associated with contracting this disease, proper food safety measures should be applied to high-risk food products including poultry, beef, pork, lamb, eggs, and fresh produce. Food manufacturers, ingredient suppliers, restaurants, and home cooks should practice sanitary processing procedures, store foods below 41 degrees Celsius, and thoroughly cook all foods to their designated safe-to-eat temperatures .It has become increasingly difficult to mitigate the presence of salmonellosis infections across the human population due to the unique nature of multidrug-resistant serovars as a result of the counterproductive effects to use antibiotics as a broad spectrum treatment. 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. 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.

Madison’s part (Iron uptake & Survival's):

Iron uptake and metabolism by ''Salmonella Enterica subsp. enterica'':

Serovars of the genus Salmonella bonded with lower molecular weight compounds called siderophores. Sensitivity growth stimulation bioassays were performed to examine the transport of a group of siderophores and the ferroxamines. It was found that the uptake of all three ferrioxamines showed to be dependent on the transport across the outer membrane through the FoxA protein. Transport across the inner membrane of this group of ferrioxamines showed to be dependent on the periplasmic binding protein-dependent inner membrane ABC transporter. The FoxA receptor gene distribution was determined by DNA hybridization and was limited to Salmonella Enterica Subspecies. Salmonella Enterica serovar typhimurium strains were unable to utilize certain groups of the ferrioxamines as a sole source of iron. AS.Enterica serovar typhimurium strain that contained an insertion of TnphoA into the gene encodes the periplasmic binding protein element of the inner membrane transport system was unable to utilize high iron limitation.

Survival in the stomach:

Under normal circumstances, Salmonella enterica infections range from 10^6 and 10^7 bacilli. There are certain scenarios that can occur to decrease the infection risk. These include, a higher pH in the stomach, gastric resection, and treatment with anti acid buffering. It is important to note that if the stomach has a lower pH, then this helps as a defensive technique to potentially fight off this infection.

''Salmonella Enterica subsp. enterica'' virulence potential can be linked to higher survival within work that is performed outside a living organism from a human gastrointestinal model. "Food Microbiology" evaluated whether Salmonella virulence could potentially be linked to a greater ability to survive consecutive digestive environments. 13 different strains of S.enterica were selected based upon their high and low virulence phenotypes that were obtained from Dr. Daigle's Labratory. Testing included using lettuce as a food source for the strains to examine the passage through the stomach. After passage, both virulence phenotype strains survived but only the high virulence strain had a greater survival rate. These survival rates could be linked to acid and bile resistant genes that are present. Certain capacities within S.enterica that survive in the human digestion tract have a low pH of the stomach and enzymatic secretions that overall affect the virulence.

Survival and Stress:

''Salmonella enterica subsp. enterica'' can undergo a variety of different survival and stress conditions which can include temperature, chemical, and pH. This strain is considered to be mesophilic with some being able to survive extremely low or high temperatures which can range from 2°C-54°C. Sigma factors inside the cell control the gene expression and they can sense the changes in the environment from the outer membrane by activation of genes that then respond to heat stress and adapt accordingly. S.enterica also can quickly respond to cold temperatures by cold shock proteins (CSP) by synthesizing themselves so that the cell can later resume growth. Chlorine can be a chemical stressor to S.enterica because once chlorine is present, S.enterica can produce a biofilm that provides itself with a exopolysaccharide matrix that has the ability of a chemical attack against chlorine. From this, chlorine has preventative measures for biofilm formation in poultry drinking systems and this reduces the risk of S.enterica. With bacterial properties that are tied to pH levels, this can create undissociated acids that acidify the cytoplasm, disrupting the key biochemical processes. In chickens, S.enterica have a pH range of 4 to 5 in the crop from lactic acid fermentation. Successful adaptation allows S.enterica to withstand more acidic conditions, counteracting stomach antibacterial effects.

Seth's Section (Servars):

Salmonella enterica subsp. enterica serovars are defined based on their somatic (O) and flagellar (H) antigens, with over 2,600 serovars in total; only about 50 of these serovars are common causes of infections in humans. Most of these serovars are found in the environment and survive in plants, water, and soil; many serovars have broad host ranges that allow them to colonize different species in mammals, birds, reptiles, amphibians, and insects. Zoonotic diseases, like Salmonella, spread between the environment and people.

'''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]'''

The CDC publishes a Salmonella Annual Report with a list of serovars most commonly associated with human illness, the top 10 serovars are listed below : (Changed data in table, as serovar host range is not critical information. Relative percentage of annual infection better portrays the importance of subsp. enterica as this subsp. has majority of infectious serovars.) Studies have concluded most strains of Salmonella enterica subsp. enterica serovars possess serotype-specific virulence plasmids. These are plasmid-associated virulence characterized by low-copy-number plasmids and depending on the serovar, its size ranges from 50 to 100 kb. In 2012, CDC's PulseNet became aware of a emergent multi-drug resistant Serovar Infantis SNP cluster, named REPJFX01. This SNP cluster has a large megaplasmid (pESI) that contains multiple drug-resistance genes. The USDA NARMS stated that because of this pESI-plasmid, serovar Infantis is the leading serovar in poultry. NCBI has over 12,500 isolates in the REPJFX01 SNP cluster, with over 3,700 being clinical isolates. Serovar Enteritidis, which is the most common serovar isolated in human clinical cases, has also been found to produce endotoxins, coded by the stn and slyA genes, that attribute to the pathogenicity of Enteritidis.

Tia (Nomenclature):

The nomenclature of Salmonella enterica has long been a topic of debate in the microbiology community. Originally in the 1880s, Salmonella species were named after the disease, host, or geological location they were associated with; however, this taxonomic characterization was contested due to genus members being categorized incompatibly with their genetic similarities. In the 1980s, the emergence of nucleotide sequencing and DNA hybridization led many established bacteriologists such as Le Minor and Popoff (1987), Euzéby (1999), and Ezaki and Yabuuchi (2000) to put forth their proposals for nomenclature changes to the Judicial Commission. It was not until 2005, that Le Minor and Popoff reproposed and established that "Salmonella enterica" would be the approved species name- excluding Salmonella bongori- and that Salmonella enterica contains six subspecies, of which, Salmonella enterica subsp. enterica contains the most serovars. Today, technological advancements allow researchers to use whole genome sequencing data to identify and group serovars using two methods: sequence typing and antigen recognition.

In terms of written serovar nomenclature, it is widely accepted that serovar names are capitalized but not italicized or underlined. Serovars may be designated in full form or short form (includes just the genus and serovar names). For example, in full designation Salmonella enterica subsp. enterica serovar Typhi is written as such, but in short designation it is written as Salmonella Typhi. Each serovar can have many strains, as well, which allows for a rapid increase in the total number of antigenically variable bacteria.