Essay about Salmonella enterica typhi

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Salmonella enterica typhi


Worldwide, typhoid fever affects roughly 17 million people annually, causing nearly 600,000 deaths. The causative agent, Salmonella enterica typhi (referred to as Salmonella typhi from now on), is an obligate parasite that has no known natural reservoir outside of humans. Little is known about the historical emergence of human S. typhi infections, however it is thought to have caused the deaths of many famous figures such as British author and poet Rudyard Kipling, the inventor of the airplane, Wilbur Wright, and the Greek Empire’s Alexander the Great. The earliest recorded epidemic occurred in Jamestown, VA where it is thought that 6,000 people died of typhoid fever in the early 17th
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It also produces no gas when grown in TSI media, which is used to differentiate it from other Enterobacteriaceae.

Typhoid/ Enteric Fever:

Infection of S. typhi leads to the development of typhoid, or enteric fever. This disease is characterized by the sudden onset of a sustained and systemic fever, severe headache, nausea, and loss of appetite. Other symptoms include constipation or diarrhea, enlargement of the spleen, possible development of meningitis, and/or general malaise. Untreated typhoid fever cases result in mortality rates ranging from 12-30% while treated cases allow for 99% survival.

Virulence Factors:

S. typhi has a combination of characteristics that make it an effective pathogen. This species contains an endotoxin typical of Gram negative organisms, as well as the Vi antigen which is thought to increase virulence. It also produces and excretes a protein known as “invasin” that allows non-phagocytic cells to take up the bacterium, where it is able to live intracellularly. It is also able to inhibit the oxidative burst of leukocytes, making innate immune response ineffective.


The encounter of humans to S. typhi is made via fecal-oral route from infected individuals to healthy ones. Poor hygiene of patients shedding the organism can lead to secondary infection, as well as consumption of shellfish from polluted bodies
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