Gut ‘bug’ transplants can bring kids with autism lasting benefits

These fecal transplants improved both behavioral problems and tummy troubles


Kids with autism often have stomach problems. Poop transplants appear able to help.


MADISON, Wis. — Autism can make it hard for children to communicate with others and to deal comfortably with the world around them. But that’s not all. Often these kids may suffer stomach problems. One new treatment for these tummy troubles sounds gross: Give the kids microbes isolated from other people’s poop. A new study found it helped rid their stomach distress. The new gut bugs also improved behaviors linked with autism. Best of all: The benefits appear to last at least two years after the treatment ends.

Autism is a word that describes a group of disorders that happen as the brain develops. Scientists are not entirely sure what causes it, although the genes passed down from parents may play a role. (Despite some rumors to the contrary, vaccines do not cause autism.) About one in every 68 kids in the United States has been diagnosed with some form of autism. The symptoms can vary in type and severity. That’s why doctors now refer to autism disorders as falling within a broad spectrum.

Most people associate autism with certain behaviors, such as hyperactivity, repetitive actions and irritability. But some patients also have stomach problems. These can include diarrhea, stomach pain or constipation. The new findings appear to strengthen the link between tummy troubles and autism.

Scientists refer to all of the bacteria, viruses and other microbes that live in the intestines as the gut’s microbiome (My-kroh-BY-ohm). The new data now provide more evidence that the microbiome can affect behavior.

Michael Hylin is a neuroscientist — someone who studies the brain — at Southern Illinois University in Carbondale. These data are “a long way from saying there’s a cure for autism.” Still, says Hylin, who was not involved in the work, “I think it’s a promising approach. It’s one that’s worthwhile.”

The scientists linked poop with autism because kids with the disorder tend to have fewer types of microbes living in their guts than do other kids. Harvesting gut microbes from human poop (gross as it may sound) has been used for years to treat a range of other health problems. So scientists wondered whether giving kids a healthier mix of gut germs might make their bellies feel better.

And it did.

Scientists reported success from their two-year trial on July 10, here, at the Beneficial Microbes Conference.

New poop for better bellies

Rosa Krajmalnik-Brown is an environmental engineer. That’s a researcher who solves problems in ecosystems — which can include someone’s gut. She works at Arizona State University in Tempe. Children with autism have fewer types of bacteria living in their guts than do kids without autism, her team has shown. Many autistic kids lack a particular type known as Prevotella. In the gut, it helps digest things such as sugar and grains. Most children in North America have these bacteria. But her team didn’t find them in children with autism.

To test whether a more diverse set of gut microbes might help, her team gave 18 children and teenagers a gut microbe makeover. Such an experimental treatment, when given to people, is known as a clinical trial.

First, the kids were given antibiotics to kill of off all the bacteria in their guts. Next, the researchers isolated bacteria from the feces of someone with a healthy gut microbiome. Then, for eight weeks, each patient was treated with those fecal bacteria. The bacteria were delivered either as an enema (a liquid injected up a patient’s rear end) or by mouth as glasses of microbe-laced chocolate milk.

The goal was for the bacteria from the healthy person to grow in the patient with autism. Those bacterial newcomers should help patients digest food better. They might help with a host of other jobs. And any unhealthy germs still left in the gut should get crowded out by the new transplants.

The researchers first assessed changes in these kids for two months after the treatment ended. Most kids reported fewer tummy problems. They suffered less diarrhea, constipation, stomach pain and indigestion.

And the benefits weren’t limited to their gut. Behaviors associated with autism also improved. In fact, two months out, changes here were better than they had been after the transplants stopped. This suggested that benefits didn’t end when the treatments did.

The team reported its initial findings last year in the journal Microbiome. At the time, no one knew whether those benefits would last, or simply go down the toilet over time. A follow-up study suggests the benefits indeed persist.

Good gut bugs help for years

Even two years after being treated, the children with autism still hosted many of their new microbes. They had more Prevotella and other beneficial gut bacteria. In fact, the diversity of bacteria in their guts was even greater than it had been two months after their therapy had ended, Krajmalnik-Brown reports.

Stomach symptoms in some of the treated kids had worsened slightly from what they had been two months after the transplants stopped. But in most kids, their gut symptoms were still more than 60 percent better than before their treatments started.

The bugs’ effects on behavior surprised the researchers even more. The kids still had autism; it’s a life-long disorder. But a child’s level of hyperactivity or repetitive actions now tended to be lower than before the treatment.

Despite these promising changes, the researchers don’t want to make too much of the findings — at least yet. Their study was small. The treatment might not work for everyone. And it’s probably not a good idea to take in someone else’s poop without a doctor’s help. Indeed, Krajmalnik-Brown cautions: “Don’t try this at home.”

The children were all between 7 and 16 at the time of treatment. Ideally, such a therapy should begin even earlier, Krajmalnik-Brown says. Autism develops as the brain develops. Symptoms tend to first emerge when a child is only a few years old. Because younger brains are more flexible than older ones, starting bacterial transplants with preschoolers might offer better results. But it’s not something that her team can test, as they have no approval to treat such young children.

For now, the scientists know only that autistic behaviors improved after receiving new fecal bacteria. That amounts to a correlation — an apparent link between two things. It does not prove, however, that the transplant itself caused any benefits seen. Next, the scientists need to make sure that the improved behavioral symptoms are due to the fecal transplants. Krajmalnik-Brown and her colleagues plan to put that idea to the test with similar transplants in adults with autism.

Tina Hesman Saey is a senior staff writer and reports on molecular biology at Science News. She has a Ph.D. in molecular genetics from Washington University in St. Louis and a master’s degree in science journalism from Boston University.

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