Researchers from Amsterdam UMC and the University of Turku, Finland, conducted a study tracking over 10,000 individuals for six years, revealing a link between intestinal flora composition and susceptibility to severe infections like pneumonia. Among those studied, over 600 individuals with less diverse intestinal flora experienced severe infections, some resulting in fatalities (1^✔ ✔Trusted Source
Study shows diverse gut bacteria communities protect against harmful pathogens by nutrient blocking

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Published in The Lancet Microbe, the study found that those hospitalized for infections initially had lower levels of butyrate-producing bacteria in their microbiome. Butyrate, a beneficial fatty acid known for its immune-boosting properties in mice, has previously been associated with reduced infection risk in humans.

Understanding the Impact of Butyrate-Producing Bacteria on Human Immunity

“But we didn’t know whether the less healthy gut flora is due to the acute infection and its treatment or whether they have always had less of the butyrate-producing bacteria in their microbiome,” says PhD student Bob Kullberg. “The study now answers this chicken-and-egg question.”

The researchers wanted to know whether, just like in mice, butyrate also has a beneficial effect on the immune system in humans. The study analyzed stool samples from more than 10,000 people (6,000 from the Finnish FINRISKI cohort and more than 4,000 Dutch participants from the HELIUS cohort).

In the study, the researchers analyzed 16 bacteria that make butyrate during the the fermentation of dietary fiber. Humans can’t digest fiber on their own, but these bacteria can. The 602 patients who were hospitalized during the 6-year follow-up study had significantly fewer of these butyrate-producing bacteria in their gut compared to the remaining people in the 2 cohorts.

Impact of Butyrate-Producing Bacteria on Infection Risk

“We saw that in people who have 10% more of those bacteria in their gut, the chance of getting an infection decreases by as much as 15 to 25%,” says Kullberg. Thus, the microbiome is involved in infections outside the gut, such as lung and bladder infections. The analyses considered factors such as age, history of antibiotic use, and underlying diseases that influence gut microbiota composition and infection risk.

Butyrate thus improves the defense against infections outside the intestines. This finding emphasizes the importance of a healthy microbiome and opens doors to predicting the risk of a serious infection for each individual. But why one individual has more butyrate-producing bacteria than the other remains a question.

The question of whether something can be done to introduce these bacteria into the intestines is also still unanswered. “Follow-up research is needed to find out how we can increase the amount of butyrate with diet or probiotics, in order to prevent serious infections,” says co-researcher and professor Joost Wiersinga.

Reference:

1. Study shows diverse gut bacteria communities protect against harmful pathogens by nutrient blocking – (https://www.ox.ac.uk/news/2023-12-15-study-shows-diverse-gut-bacteria-communities-protect-against-harmful-pathogens)

Source-Eurekalert