The particular assortment of microbes in the digestive system may be an important factor in the inflammatory bowel condition known as Crohn's disease.
Research involving more than 1,500 patients found that people with Crohn's disease had less diverse populations of gut microbes.
"[This] basically for the first time identifies what might be the bacterial changes in patients with Crohn's disease," says Ramnik Xavier, of Masssachusetts General Hospital in Boston, who led the work.
More than a million Americans suffer from Crohn's, which seems to start when an overreactive immune system causes abdominal pain, diarrhea, bleeding, weight loss and other symptoms. Many patients have to take powerful steroids (which can have serious side-effects), and some have parts of the digestive tract surgically removed.
Mounting evidence has suggested that microbes living in the gut might contribute to the problem. So Xavier and his colleagues compared the species of bacteria in more than 447 Crohn's patients to the mix of microbes in more than 221 healthy people.
In their paper published in the journal Cell, Host and Microbe, the researchers detailed the clear difference they discovered: The patients with Crohn's seemed to have too many of the sorts of bacteria that rile immune systems.
In addition to having less diversity in their gut microbes, Xavier says, the Crohn's patients had fewer bacteria that have been associated with reduced inflammation and more bacteria associated with increased inflammation. (The findings were confirmed in 800 Crohn's patients from other studies.)
Interestingly, children whose doctors had tried to treat their Crohn's symptoms with antibiotics before they were properly diagnosed had a mix of microbes that was the most out of whack.
"We may have to revisit the use of antibiotics in [these] patients with early-onset Crohn's disease," Xavier says.
Instead, doctors might eventually do better to identify and prescribe treatments that mimic the helpful bacteria, he says, along with foods or other pharmaceutical agents that reduce or counteract the harmful bacteria.
"There's the possibility that we might be able to identify [some] sort of super-probiotics that might be able to correct the gut back to the healthy state," Xavier says.
UCLA pathologist Jonathan Braun, who studies microbial ecology, says the paper offers important first insights into illnesses beyond Crohn's. "Other diseases are thought to be driven at least in part by bacteria," he says, such as some inflammatory and autoimmune disorders. Bacteria may also be involved in obesity.
Humans should work harder to understand bacteria, Braun says, "and live with them when they're helping us, or get them to serve us better when they are causing harm."
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The bacteria that live in your gut are important to your health. That's becoming increasingly clear, thanks to a growing body of scientific research. And today, there's a new study that links the mix of those bacteria to a common disorder of the digestive system. It's called Crohn's disease.
Here's NPR's Rob Stein.
ROB STEIN, BYLINE: Crohn's disease is an awful, chronic condition. It affects more than a million Americans. Ramnik Xavier, at the Massachusetts General Hospital in Boston, says it happens when the immune system kind of goes berserk.
RAMNIK XAVIER: Patients usually present with abdominal pain and diarrhea. They can have bleeding and weight loss.
STEIN: Many patients have to take powerful steroids that can have serious side effects. Some end up getting parts of their digestive tracts surgically removed. But evidence has been mounting that the microbes that live in the gut may be playing a role. So Xavier and his colleagues compared the microbes in more than 400 Crohn's patients, to the microbes in more than 200 healthy people. And they found a clear difference. First of all, the Crohn's patients had far less diverse microbes. And...
XAVIER: The good bacteria, the bacteria that prevent inflammation, had decreased. And the bacteria that promote inflammation, which we refer to as the bad bacteria, had increased.
STEIN: That indicates that one reason why Crohn's patients have problems is because their mix of microbes is out of whack. They have too much of the kind of bacteria that riles up their immune systems.
XAVIER: What it basically, for the first time, identifies what might be the bacterial changes in patients with Crohn's disease.
STEIN: The researchers confirmed the findings in 800 more Crohn's patients. The findings suggest that drugs that mimic the good bacteria, and things that reduce the bad bacteria, may help treat Crohn's.
XAVIER: There is the possibility that we might be able to identify sort of super-probiotics that might be able to correct the gut back to the healthy state.
STEIN: Other researchers agree the findings could lead to better ways to diagnose and treat Crohn's. Here's Jonathan Braun, from UCLA.
JONATHAN BRAUN: This is an important paper because it gives us one of the first insights about how bacteria play a role in affecting disease states in people.
STEIN: And, Braun, says it could open the door to learning how microbes play a role in other diseases.
BRAUN: Other diseases are thought to be driven at least in part by bacteria - other inflammatory diseases, certain autoimmune diseases, and even traits like obesity. So this gives us, really, a different perspective about these bacteria and how we should come to understand them better and live with them, when they're helping us, or get them to serve us better when they are causing harm.
STEIN: The next step will be to try to figure out exactly how to manipulate our microbes, to better diagnose and treat Crohn's disease and other health problems.
Rob Stein, NPR News. Transcript provided by NPR, Copyright NPR.