A new study found that the composition of the intestinal flora can help researchers assess the risks of developing serious infections, such as pneumonia.
Researchers from the Amsterdam University Medical Center (Amsterdam UMC) and the University of Turku, Finland, followed more than 10,000 people for 6 years.
More than 600 people who had less healthy gut flora developed a serious infection, in some cases leading to death.
The 602 people who were hospitalized with an infection showed at the start of the study that they had fewer butyrate-producing bacteria in their microbiome.
Butyrate is a small fatty acid known to have a positive impact on the immune system of mice.
It has also been previously observed that people with severe infections have fewer bacteria of this type.
“We didn’t know if this less healthy gut flora was due to the acute infection and treatment, or if these individuals had always had fewer butyrate-producing bacteria in their microbiome,” says PhD student Bob Kullberg. The study now answers that chicken-or-egg question, he says.
The researchers wanted to find out whether, just like in mice, butyrate has a beneficial effect on the immune system in humans as well.
The study analyzed stool samples from over 10,000 people (6,000 from the Finnish FINRISKI cohort and over 4,000 Dutch participants from the HELIUS cohort).
In the study, the researchers analyzed 16 bacteria that produce butyrate by drugging the fermentation of dietary fiber. Humans cannot digest fiber without the help of these bacteria.
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 rest of the people in the 2 cohorts.
Researchers have observed that in people who have 10% more bacteria of this type in their gut, the chances of getting an infection decrease by up to 15-25%.
In this way, the microbiome appears to be involved in infections outside the gut, such as lung and bladder infections.
The analyzes took into account factors such as age, history of antibiotic use and underlying diseases that influence the composition of the gut microbiota and the risk of infection.
More research
This finding that butyrate improves defenses against infections outside the gut underscores the importance of a healthy microbiome and introduces new ways to estimate an individual’s risk of serious infection.
Some unanswered questions still remain, such as why one individual has more butyrate-producing bacteria than another, and whether something can be done to introduce these bacteria into the gut.
“Further research is needed to find out how we can increase the amount of butyrate through diet or probiotics to prevent serious infections,” says researcher and professor Joost Wiersinga, who led the study, in a statement from Amsterdam UMC.
