Salmonella Typhimurium is a bacterium of the bacillus type, Gram negative, flagellate, whose full name is Salmonella enterica subspecies enteric serovar Typhimurium. It is a facultative anaerobic flagellated unicellular organism, which causes the disease known as salmonellosis, a disease that attacks both humans and other animal species. The epithet Typhimurium means mouse typhus. This bacterium causes a typhus-like disease in mice.
It is included in the Bacteria domain, Proteobacteria phylum, Gammaproteobacteria class, Enterobacteriales order, Enterobacteriaceae family, genus Salmonella, and like other Enterobacteriaceae, it produces an enterotoxin that causes damage to the intestinal mucosa.
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Salmonella Typhimurium it continues its life cycle in different animal hosts, reproducing by bipartition in the small intestine. In its life process, the intestine generates toxins that cause diarrhea. Bacteria come out along with the feces, thus contaminating various surfaces.
If you eat contaminated food or have contact with contaminated surfaces and then put your hands in your mouth, the bacteria enter the digestive system, continuing the cycle.
Inside the small intestine, bacteria adhere to the cell membrane of the cells of the epithelial mucosa. Then, they penetrate cells and cause metabolic and structural damage..
The damage caused by the toxins of the bacteria generates gastroenteritis or inflammation of the inner lining of the intestine. The disease manifests itself with diarrhea, vomiting and abdominal pain. This disease is not fatal except in cases of the elderly, children or those who have a depressed immune system.
Salmonella Typhimurium eIt is a bacillus-like bacteria, that is, a single-celled organism shaped like a short bar. Negative on Gram stain.
It has a plasma membrane surrounded by a thin peptoglycan cell wall and an outer plasma membrane. Like all bacteria, it does not have a defined nucleus. It is mobilized thanks to the presence of several flagella arranged around it (peritrichous flagella).
The outer membrane plays an important role. In it, the protein chains that recognize the specific receptors on the surface of the epithelial cells of the intestine (adhesins) are produced. In this way the bacteria can adhere to the intestinal wall. On Salmonella Typhimurium no capsule is formed.
Its genetic material (DNA) is found on a circular chromosome. Additionally, it has a plasmid or small DNA ring that provides extra genetic information, especially linked to its pathogenicity, that is, its ability to cause disease..
The genome of Salmonella Typhimurium it is organized on a circular chromosome and on an additional plasmid. The complete sequence of the genome of Salmonella enterica serovar Typhimurium LT2, reaching 4,857,000 base pairs on the chromosome and 94,000 base pairs on the plasmid responsible for virulence.
Several of the so-called islands of pathogenicity have been detected. These are specific areas where there are gene sequences responsible for different actions that allow the bacterium to attach to the host's cells, produce enterotoxin, and other processes related to its ability to produce disease..
Salmonella Typhimurium belongs to the domain Bacteria, phylum Proteobacteria, class Gammaproteobacteria, order Enterobacteriales, family Enterobacteriaceae, genus Salmonella.
The taxonomy of the genus Salmonella Is very complicated. In general, in all bacteria it is, due to its scarce morphological characteristics to differentiate species.
In this case the experts decided to divide the gender Salmonella in two species. These species are differentiated by metabolic characteristics, which is detected by checking whether or not they hydrolyze certain substances or if they are capable of growing in certain culture media..
The two species are Salmonella enterica Y Salmonella bongori. In turn, these species are divided into subspecies and more than 2,500 serovars. The serovars are determined according to associations of antigens to which they react.
In our case, the species Salmonella enterica is divided into six subspecies, one of them is Salmonella enterica subspecies enteric. Salmonella Typhimurium is a serovar of this subspecies.
His full name is Salmonella enterica subspecies enteric serovar Typhimurium. But conventionally, only gender and serovar are indicated: Salmonella Typhimurium.
Salmonella Typhimurium it reproduces by bipartition or binary fission. That is, the only cell that makes up this organism divides in two by constriction. In this way two genetically identical individuals (clones) originate. Bacterial reproduction occurs in the small intestine of the host animal.
Once the reproduction has occurred, the bacteria are released into the external environment mixed with the feces. The action of the enterotoxin of the bacteria promotes diarrhea with it provides a means of dispersal for itself.
Outside, feces contaminate various surfaces. Other animals of the same species or others, ingest the bacteria, either by consuming contaminated food or having contact with contaminated matter that is taken to the mouth. In this way, the bacteria reach the small intestine again and continue their life cycle..
Salmonella Typhimurium it is distributed worldwide. It inhabits various animal hosts: birds, cattle and pigs, rodents, dogs, cats, iguanas, turtles and humans.
It survives in areas contaminated by the feces of these animals. These include water, soil, ceramics, stainless steel, fruit and vegetable surfaces such as tomatoes, chili peppers, melons, among others..
Its optimum temperature is between 35 and 43 ºC. However, it is capable of surviving low temperatures down to 5.2 ºC and die at temperatures above 46.2 ºC. On the other hand, for their survival they require moisture on the surface where they live..
Salmonella Typhimurium it causes the disease known as salmonellosis or more generically gastroenteritis. The disease attacks humans and other animal species.
It occurs due to the action of the bacteria that live in the small intestine. There it invades the epithelium of the intestine and secretes an enterotoxin that penetrates the cells of the intestine. This enterotoxin is 98% similar to the enterotoxin of Vibrio cholerae (CT).
It is estimated that there are more than 1.3 billion cases of gastroenteritis per year in the world. In an average of 3 million cases the disease is fatal. Likewise, the losses in the poultry industry are important.
The sequence of events that determine the pathogenesis of Salmonella Typhimurium includes adherence to the epithelial cell surface. Later the invasion of the bacteria into the host cell.
Once inside, it causes metabolic imbalances that cause the activation of the enzyme adenylate cyclase, destruction of villi, secretion of pro-inflammatory cytosines, decreased intestinal absorption capacity, among other effects..
The action of the enzyme adenylate cyclase generates the production of intracellular cyclic adenosine monophosphate, triggering the pumping of large amounts of water and electrolytes through the cell membranes of epithelial cells. The epithelial mucosa of the intestine is also damaged and inflammation occurs. All this produces diarrhea.
The bacteria are spread in two ways. One occurs when cellular self-destruction mechanisms (apoptosis) are activated, thus leaving the bacteria free. It can also move inside macrophages that have been invaded.
Macrophages are cells of the immune system that move through the circulatory system. They are an important part of the immune system with the function of engulfing malignant bacteria. However, Salmonella Typhimurium and other pathogenic bacteria have mechanisms that allow them to be swallowed, but not destroyed.
Salmonella Typhimurium it can reach the liver and spleen by an alternate route, which does not require intestinal colonization or invasion of intestinal epithelial cells. This is possible thanks to its ability to colonize macrophages..
From 6 to 72 hours after exposure to the bacteria, symptoms appear. Nausea, vomiting, headache, fever, abdominal pain and diarrhea occur.
These symptoms last 4 to 7 days. The development of the disease depends on the conditions of the host or patient, the dose ingested and the specific strain of bacteria..
In children, the elderly and immunosuppressed people, special care must be taken, since dehydration can occur that can cause death..
In some cases there may be complications. Infection can become general when bacteria invade the blood (septicemia), or an autoimmune reaction can develop and cause reactive arthritis 3 to 4 weeks after the onset of acute symptoms.
It is necessary to maintain surveillance and control measures on farms in order to avoid the commercialization of sick animals. Proper hygiene practices must be followed in production structures.
Eating raw or undercooked foods should be avoided. In the case of fruits and vegetables, wash them properly with boiled or filtered water. Consume pasteurized milk and derivatives.
The main thing to prevent contagion is personal hygiene and hygiene in food production or consumption areas. Wash your hands well before and after handling food or before consuming it. Likewise, keep all work instruments in the kitchen clean.
The bacterium is sensitive to heat and to disinfectants commonly used in the food industry. If chlorine is applied for 5 minutes it is enough to eliminate it.
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