The same strain can be harmless or harmful depending entirely on its environment.
In the hidden ecosystem of the small intestine, researchers at Washington University have uncovered a troubling inheritance: the inflammatory bacteria behind environmental enteric dysfunction — a condition that stunts the bodies and minds of millions of children in the world's poorest regions — can be passed from mother to child before birth itself. Led by Jeffrey Gordon and grounded in fieldwork among malnourished children in Bangladesh, the study reveals that disease is not merely a consequence of poverty and hunger, but may be carried forward in the very microbial communities a mother transmits to her unborn offspring. This discovery reframes malnutrition not as a problem that begins at the table, but as one that may begin in the womb — and it opens a new chapter in the long human effort to break cycles of suffering that span generations.
- Millions of children treated for malnutrition still suffer stunted growth and cognitive deficits because the underlying gut damage — environmental enteric dysfunction — persists long after supplemental food is provided.
- Washington University researchers found that the inflammatory bacteria driving this damage are transmitted from mothers to offspring in utero, before the newborn has developed any microbiome of its own.
- Mouse studies confirmed the mechanism: offspring of mothers colonized with bacteria from malnourished Bangladeshi children developed the same intestinal damage, inflammation, and stunted growth — beginning before birth.
- A key culprit, Campylobacter concisus, proved harmless in isolation but pathogenic within the wrong microbial community, revealing that context — not just the presence of a bacterium — determines whether disease takes hold.
- The research team is now working to identify safe microbiome interventions during pregnancy that could reshape the maternal gut environment and prevent transmission of harmful bacteria to the next generation.
Deep within the small intestine — an organ nearly impossible to study in living children — an ecosystem of bacteria may be quietly passing disease from one generation to the next. Researchers at Washington University School of Medicine have found that the inflammatory gut bacteria behind environmental enteric dysfunction, or EED, can be transmitted from mothers to their offspring before birth, with consequences that ripple across a lifetime.
EED damages the intestinal lining, blocking nutrient absorption and leaving children with stunted growth, weakened immunity, and cognitive delays that persist into adulthood even after nutritional treatment. The condition is widespread across South Asia and sub-Saharan Africa. In Bangladesh, 525 malnourished children averaging 18 months old — none of whom had responded to standard therapeutic nutrition — were enrolled in a study led by Jeffrey Gordon. Using endoscopy, researchers sampled tissue and bacteria from the children's upper small intestines and identified 14 bacterial strains linked to inflammation and stunted growth.
To understand whether these bacteria could cause disease and spread between generations, the team turned to mice. Animals colonized with the inflammatory bacterial collections from the Bangladeshi children developed intestinal inflammation — and when they became pregnant, their offspring showed the same stunted growth, blood inflammation markers, and intestinal damage seen in the children. Crucially, this damage began before birth, before the pups had developed any microbiome of their own. The researchers also found that harmful bacteria spread between mice housed together, suggesting the disease can move through proximity and contact.
One strain stood out: Campylobacter concisus, ordinarily harmless in the mouth, became pathogenic when it took hold in the small intestine — but only within the right microbial context. Introduced alone into germ-free mice, it neither caused disease nor survived well. The finding underscores a fundamental truth about microbial life: the same bacterium can be harmless or devastating depending entirely on its surroundings.
The implications point toward a new frontier of intervention. If harmful bacteria are transmitted before birth, reshaping the maternal microbiome during pregnancy could break the cycle — not by sterilizing the gut, but by tipping its balance toward health. For the millions of children whose growth and cognition are compromised before they ever take their first breath, this research suggests that the most powerful moment to intervene may arrive before the next generation is even born.
In the small intestine—a place almost impossible to study in living children—lives an ecosystem that may be quietly passing disease from one generation to the next. Researchers at Washington University School of Medicine have found evidence that inflammatory bacteria in the gut can be transmitted from mothers to their offspring, and that this transmission begins before birth, in the womb itself.
The disorder in question is called environmental enteric dysfunction, or EED. It damages the lining of the small intestine, preventing the body from absorbing nutrients properly. Children with EED suffer stunted growth, weakened immunity, and cognitive delays—problems that follow them into adulthood even after their malnutrition is treated with supplemental food. The condition is widespread in low-income countries, particularly in South Asia and sub-Saharan Africa. In Bangladesh, where much of this research took place, hundreds of malnourished children were enrolled in a study to understand what was happening in their guts.
The researchers, led by Jeffrey Gordon, worked with colleagues in Bangladesh to collect samples from 525 children, averaging 18 months old, who had not improved despite receiving standard therapeutic nutrition containing milk, eggs, vitamins, and minerals. Using endoscopy—a procedure requiring parental consent—they sampled tissue and bacteria from the children's upper small intestines. They identified 14 types of bacteria linked to stunted growth and inflammation. The next step was to understand whether these bacteria could actually cause the disease, and whether they could spread between generations.
To test this, the researchers used mice. They fed the animals a diet similar to what children in the Mirpur district of Dhaka typically eat. Some of the mice, born without any gut bacteria, were colonized with the inflammatory bacterial collections taken from the malnourished children. Other mice received a different bacterial collection from the same children that did not cause inflammation—this served as a control group. The inflammatory bacteria induced intestinal inflammation in the female mice. When these females became pregnant and gave birth, something striking happened: their offspring developed the same problems as the children in Bangladesh. The pups showed stunted growth, markers of inflammation in their blood, and damage to their intestinal lining. Most remarkably, this damage began before birth, before the offspring had any bacteria of their own.
The researchers also discovered that when mice with inflammatory bacteria were housed together with mice that had been given the non-inflammatory bacterial collection, the harmful bacteria spread to the previously unaffected animals. This suggests that the disease is not locked within a single organism but can move between individuals through proximity and contact.
Among the bacterial strains identified, one stood out: Campylobacter concisus. This microbe, typically found in the human mouth where it causes no known problems, became pathogenic when it established itself in the small intestine. Yet when researchers gave C. concisus to germ-free mice—animals with no bacteria at all—the microbe neither caused disease nor survived well. This paradox reveals something fundamental about how bacteria work: the same strain can be harmless, helpful, or harmful depending entirely on its environment and the other bacteria around it.
The implications are profound. If inflammatory bacteria can be passed from mother to child before birth, and if they can spread between individuals, then interventions during pregnancy might break the cycle. Gordon and his team are now working to identify safe ways to shift the maternal microbiome toward a healthier state—one that would reduce inflammation in the mother while establishing a stable, beneficial bacterial environment in her offspring. The goal is not to sterilize the gut but to reshape it, to tip the balance away from disease and toward health. For millions of children worldwide living with stunted growth and cognitive deficits that persist throughout their lives, this research suggests a new point of intervention: not after malnutrition has taken hold, but before the next generation is even born.
Notable Quotes
The gut microbes in the small intestine make up a largely unexplored ecosystem—a 'terra incognita'—because they are difficult to sample.— Jeffrey I. Gordon, senior author and director of the Edison Family Center for Genome Sciences & Systems Biology at Washington University School of Medicine
It highlights how nuanced these interactions are between different bacteria and how they contribute to disease in some contexts but not others.— Kali M. Pruss, first author and instructor of pathology and immunology at Washington University School of Medicine
The Hearth Conversation Another angle on the story
Why is the small intestine so hard to study in living children?
You can't just biopsy a healthy child's gut without ethical justification. An endoscopy is invasive. So researchers have to work with samples from children who are already sick and undergoing the procedure for medical reasons. It's a constraint that shapes what we can know.
So they used mice instead. But why would bacteria from a Bangladeshi child's gut behave the same way in a mouse?
The diet matters enormously. They fed the mice foods typical of where those children lived—the same staple grains, the same nutritional profile. The bacteria evolved in that context. Put them in a different food environment, and they might behave completely differently. That's why the experimental design was so careful.
The fact that Campylobacter concisus didn't survive alone in germ-free mice—what does that tell us?
It tells us bacteria aren't independent agents. They're part of a community. C. concisus needs other bacteria around it to thrive and to cause harm. It's like saying a single instrument can't make a symphony. You need the ensemble.
If the damage happens in utero, before the baby has any bacteria, how is that possible?
The mother's bacteria aren't directly in the fetus. But they're producing inflammatory signals—chemical messengers—that cross the placenta and affect fetal development. The bacteria themselves don't have to be present for their effects to be felt.
What happens if researchers can shift a mother's microbiome before she gets pregnant?
That's the hope. If you can reduce the inflammatory bacteria and establish a healthier community, her offspring might be born into a different microbial world—one that supports growth instead of stunting it. It's prevention at the source.