Research: Salmonella live on thanks to toxin
A toxin protein secreted by typhoid-causing bacteria seems to keep infected hosts alive, allowing the bacteria to persist in the body.
Salmonella enterica Typhi (S. Typhi), which causes typhoid fever in humans but not in mice, produces a DNA-damaging protein. To study this toxin's role in mouse infections, Teresa Frisan at the Karolinska Institute in Stockholm and her team engineered another strain of S. enterica, called S. Typhimurium (which causes illness in mice but does not normally make the typhoid toxin) to make the part of the toxin that damages host DNA.
Mice infected with the toxin-producing strain were less likely to become severely ill and had less gut inflammation than did mice infected with a control strain. Toxin-producing bacteria could still be found in the livers of mice six months after infection, in contrast to the control strain, which was undetectable in mice that survived the initial infection.
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