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Powerful toxin gives Salmonella typhi its lethality according to study

Researchers from Yale University believe they understand how typhoid fever kills some 200,000 people and affects about 21.5 million persons each year.

Salmonella image/CDC

Salmonella image/CDC

The new research, Structure and function of the Salmonella Typhi chimaeric A2B5 typhoid toxin,  is published in the journal, Nature.

The culprit appears to be a powerful toxin possessed by Salmonella typhi, the bacterium that causes typhoid fever. Yale scientists for the first time describe the structure of the typhoid toxin and show that it causes disease in mice. The toxin helps explain why typhoid fever has such different symptoms than an infection by its close genetic cousin Salmonella, the common cause of food poisoning, according to Yale News.

In the article preview in the journal, researchers say:

Here we find that the systemic administration of typhoid toxin, a unique virulence factor of S. Typhi, reproduces many of the acute symptoms of typhoid fever in an animal model. We identify specific carbohydrate moieties on specific surface glycoproteins that serve as receptors for typhoid toxin, which explains its broad cell target specificity. We present the atomic structure of typhoid toxin, which shows an unprecedented A2B5 organization with two covalently linked A subunits non-covalently associated to a pentameric B subunit. The structure provides insight into the toxin’s receptor-binding specificity and delivery mechanisms and reveals how the activities of two powerful toxins have been co-opted into a single, unique toxin that can induce many of the symptoms characteristic of typhoid fever.

“What makes this so exciting for us is that vaccines and therapeutics that target toxins have an excellent track record of success,” said Jorge Galan, the Lucille P. Markey Professor of Microbial Pathogenesis and senior author of the paper.

Typhoid fever is a potentially life-threatening illness caused by the bacterium Salmonella typhi. Salmonella typhi lives only in humans. Persons with typhoid fever carry the bacteria in their bloodstream and intestinal tract. In addition, a small number of persons, called carriers, recover from typhoid fever but continue to carry the bacteria. Both ill persons and carriers shed S.typhi in their feces.

You can get typhoid fever if you eat food or drink beverages that have been handled by a person who is shedding S. typhi or if sewage contaminated with S. typhi bacteria gets into the water you use for drinking or washing food. Therefore, typhoid fever is more common in areas of the world where handwashing is less frequent and water is likely to be contaminated with sewage.

Typhoid fever can be successfully treated with appropriate antibiotics, and persons given antibioticsusually begin to feel better within 2 to 3 days.

Learn more about typhoid fever in this educational video

For more infectious disease news and information, visit and “like” the Infectious Disease News Facebook page

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About the Author

- Writer, Co-Founder and Executive Editor of The Global Dispatch. Robert has been covering news in the areas of health, world news and politics for a variety of online news sources. He is also the Editor-in-Chief of the website, Outbreak News Today and hosts the podcast, Outbreak News Interviews on iTunes, Stitcher and Spotify Robert is politically Independent and a born again Christian Follow @bactiman63

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