Salmonella bacteria can inhibit the loss of appetite that often accompanies bacterial infection, probably to boost the microbe's spread to new hosts.
Janelle Ayres and her team at the Salk Institute for Biological Studies in La Jolla, California, fed mice that had previously been kept pathogen-free with strains of Salmonella enterica serovar Typhimurium (S. Typhimurium; pictured). They found that a protein secreted by S. Typhimurium during infection, called SlrP, blocks molecular signalling between the gut and the brain by interfering with inflammatory processes. As a result, although the infected animals ate less than normal, the decrease in their food intake was less marked than in mice infected with a mutant strain that lacked this protein. Fewer of the animals carrying the mutant bacteria shed it in their faeces, even though the bacteria had spread throughout the body more often than in mice infected with normal S. Typhimurium.
Limiting appetite loss is advantageous for both S. Typhimurium transmission and host survival, the authors say.
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Salmonella makes hosts eat. Nature 542, 8–9 (2017). https://doi.org/10.1038/542008d