When people are ill due to food poisoning the common behaviour is to eat less and sleep. This strategy, medics have found is beneficial in helping those afflicted, to recover. However, this may not be appropriate in all cases, as new research indicates.
Research into one type of Salmonella bacterium found that the organism can actually encourage rodents to eat more, by affecting the vagus nerve to the brain, and this decreases the fatality rate.
The study was performed by immunomicrobiologist Dr. Janelle Ayres who works at the Salk Institute for Biological Studies in San Diego, California. The aim of the research, according to the magazine Science, was to determine the effect of reduced eating on a Salmonella bacterium. The study involved infecting test mice with the bacterium; here it was observed that a bacterial protein termed SlrP (small leucine-rich proteoglycan) altered how the infectivity of the organisms. Proteoglycans are a major component of the animal extracellular matrix, the “filler” substance existing between cells in an organism.
Specifically, bacteria that did not produce the protein were more likely to kill the rodents. Interestingly, mice infected by the bacteria without the SlrP protein ate 20 percent less than control mice.
The findings indicate result Salmonella bacteria deploy SlrP to manipulate the appetite of those they infect. When a mouse is infected with Salmonella the vagus nerve dispatches signals to the hypothalamus that signals to the rodents to reduce their food intake. However, when SlrP is present it blocks the brain-gut signals. The consequence is that the mice eat more and these mice are more likely to survive.
This is because when the animal does not eat the bacteria find it easier to leave the gut and to infect other organs, like the liver; whereas, when the animal eats the organisms are easier to contain and the survival rate increases.
The research is published in the journal Cell, titled “Pathogen-Mediated Inhibition of Anorexia Promotes Host Survival and Transmission.”
