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Lack of enzyme explains why typhoid fever is a human-specific disease

The bacterium Salmonella Typhi causes in humans, but leaves other mammals unaffected. Researchers at , and Yale University Schools of Medicine now offer one explanation — CMAH, an enzyme that humans lack. Without this enzyme, a toxin deployed by the bacteria is much better able to bind and enter human cells, making us sick. The study is published in the journal Cell.

[Typhoid Graphic]
Due to a single oxygen atom difference in sialic acids, typhoid toxin affects humans while other mammals are resistant.


Co-authors include Lingquan Deng, Nissi Varki, , UC San Diego School of Medicine; Jeongmin Song, Xiang Gao, ; Jiawei Wang, Tsinghua University; Hai Yu, Xi Chen, University of California, Davis.

This research was funded, in part, by the National Cancer Institute (grant CA38701) and the National Institute of Allergy and Infectious Diseases (grant AI079022), both part of the U.S. National Institutes of Health.

University of California – San Diego