Fasting before and during exposure to Salmonella enterica bacteria
protects mice from developing a full-blown infection, in part due to
changes in the animals' gut microbiomes, according to new research
published in PLOS Pathogens by Bruce Vallance and colleagues at University of British Columbia, Canada.
When people or animals develop an infection, they often lose their appetite. However it remains controversial whether fasting protects a host from infection, or increases their susceptibility. In the new study, mice were fasted for 48 hours before and during oral infection with the bacteria Salmonella enterica serovar Typhimurium, a common cause of foodborne illness in people.
Fasting
decreased the signs of bacterial infection compared to fed mice,
including nearly eliminating all intestinal tissue damage and
inflammation. When fasted animals were re-fed for a day after their
fast, there was a dramatic increase in Salmonella numbers
and invasion into the intestinal walls, although the associated
inflammation was still attenuated compared to normal. The results did
not hold true when mice were exposed to Salmonella intravenously
instead of orally, and analyses of the microbiomes of mice showed
significant changes associated with fasting and protection against
infection. Moreover, fasting did not fully protect germ-free mice—bred
to lack a normal microbiome—from Salmonella, suggesting that some of the protection was due to fasting's effect on the microbiome. Experiments using the bacteria Campylobacter jejuni confirmed that the effect of fasting was not limited to Salmonella, with similar results seen.
"These data suggest that therapeutic fasting or calorie restriction has
the potential to beneficially modulate infectious and potentially
non-infectious gastrointestinal diseases," the researchers conclude.
The
researchers add, "Our research highlights the important role that food
plays in regulating interactions between the host, enteric pathogens and
the gut microbiome.
When food is limited, the microbiome appears to sequester the nutrients
that remain, preventing pathogens from acquiring the energy they need
to infect the host. While more research is needed, fasting or otherwise
adjusting food intake could be exploited therapeutically to modulate infectious diseases in the future."
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