Eating more fiber supports growth of good bacteria and protects against gut infections

The group of bacteria called Enterobacteriaceae, including Klebsiella pneumoniae, Shigella, E.coli and others, is present at low levels as part of a healthy human gut microbiome. But at high levels - caused for example by increased inflammation in the body, or by eating contaminated food - these bugs can cause illness and disease. In extreme cases, too much Enterobacteriaceae in the gut can be life-threatening.

Researchers have used computational approaches including AI to analyze the gut microbiome composition of over 12,000 people across 45 countries from their stool samples. They found that a person's microbiome 'signature' can predict whether a person's gut is likely to be colonized by Enterobacteriaceae. The results are consistent across different states of health and geographic locations.

The researchers identified 135 gut microbe species that are commonly found in the absence of Enterobacteriaceae, likely protecting against infection.

Notable amongst the protective gut species are a group of bacteria called Faecalibacterium, which produce beneficial compounds called short-chain fatty acids by breaking down fiber in the foods we eat. This seems to protect against infection by a range of disease-causing Enterobacteriaceae bugs.

The researchers suggest that eating more fiber in our diet will support the growth of good bacteria - and crowd out the bad ones to significantly reduce the risk of illness.

In contrast, taking probiotics - which don't directly change the environment in the gut - is less likely to affect the likelihood of Enterobacteriaceae infection.

The results are published today in the journal Nature Microbiology. 

Our results suggest that what we eat is potentially very important in controlling the likelihood of infection with a range of bacteria, including E.coli and Klebsiella pneumoniae, because this changes our gut environment to make it more hostile to invaders."

Dr. Alexandre Almeida, researcher at the University of Cambridge's Department of Veterinary Medicine and senior author of the paper

He added: "By eating fiber in foods like vegetables, beans and whole grains, we can provide the raw material for our gut bacteria to produce short chain fatty acids - compounds that can protect us from these pathogenic bugs."

Klebsiella pneumonia can cause pneumonia, meningitis and other infections. The alarming global rise in antibiotic resistance to this bacterial pathogen has led scientists to look for new ways of keeping it, and other similar infectious bacteria, under control. 

"With higher rates of antibiotic resistance there are fewer treatment options available to us. The best approach now is to prevent infections occurring in the first place, and we can do this by reducing the opportunities for these disease-causing bacteria to thrive in our gut," said Almeida.

A new understanding of gut microbe interactions

Earlier research to understand interactions between the different bacteria in our gut has used mouse models. But some of these new results are at odds with previous findings. 

The new study revealed that 172 species of gut microbe can coexist with disease-causing Enterobacteriaceae bugs. Many of these species are functionally similar to the bugs: they need the same nutrients to survive. Previously it was thought that competition for resources would stop the disease-causing bacteria from getting established in the gut.

This has important implications for treatment: taking probiotics that compete for the same nutrients with the bad bacteria to try and starve them out isn't going to work. The researchers say that it will be more beneficial to change the environment in the gut, for instance through diet, to reduce the risk of infection with Enterobacteriaceae.

"This study highlights the importance of studying pathogens not as isolated entities, but in the context of their surrounding gut microbiome," said Dr Qi Yin, a visiting researcher at the University of Cambridge's Department of Veterinary Medicine and first author of the report.