In 2008, Dr. Khoruts, a gastroenterologist at the University of Minnesota, took on a patient suffering from a vicious gut infection of Clostridium difficile. She was crippled by constant diarrhea, which had left her in a wheelchair wearing diapers. Dr. Khoruts treated her with an assortment of antibiotics, but nothing could stop the bacteria. His patient was wasting away, losing 60 pounds over the course of eight months. “She was just dwindling down the drain, and she probably would have died,” Dr. Khoruts said.Isn't it odd to realize that over a century after "modern medicine" established itself, a "miracle" cure as simple as re-colonizing a patient with a new set of bacteria, a new microbiome, can be discovered.
Dr. Khoruts decided his patient needed a transplant. But he didn’t give her a piece of someone else’s intestines, or a stomach, or any other organ. Instead, he gave her some of her husband’s bacteria.
Dr. Khoruts mixed a small sample of her husband’s stool with saline solution and delivered it into her colon. Writing in the Journal of Clinical Gastroenterology last month, Dr. Khoruts and his colleagues reported that her diarrhea vanished in a day. Her Clostridium difficile infection disappeared as well and has not returned since.
The procedure — known as bacteriotherapy or fecal transplantation — had been carried out a few times over the past few decades. But Dr. Khoruts and his colleagues were able to do something previous doctors could not: they took a genetic survey of the bacteria in her intestines before and after the transplant.
Before the transplant, they found, her gut flora was in a desperate state. “The normal bacteria just didn’t exist in her,” said Dr. Khoruts. “She was colonized by all sorts of misfits.”
Two weeks after the transplant, the scientists analyzed the microbes again. Her husband’s microbes had taken over. “That community was able to function and cure her disease in a matter of days,” said Janet Jansson, a microbial ecologist at Lawrence Berkeley National Laboratory and a co-author of the paper. “I didn’t expect it to work. The project blew me away.”
On his blog, Carl Zimmer points to a CalTech press release of a new research result:
Biologists at the California Institute of Technology (Caltech) have demonstrated a connection between multiple sclerosis (MS)—an autoimmune disorder that affects the brain and spinal cord-and gut bacteria.
Although the cause of MS is unknown, microorganisms seem to play some sort of role. "In the literature from clinical studies, there are papers showing that microbes affect MS," Mazmanian says. "For example, the disease gets worse after viral infections, and bacterial infections cause an increase in MS symptoms."
On the other hand, he concedes, "it seems counterintuitive that a microbe would be involved in a disease of the central nervous system, because these are sterile tissues."
And yet, as Mazmanian found when he began examining the multiple sclerosis literature, the suggestion of a link between bacteria and the disease is more than anecdotal. Notably, back in 1993, Caltech biochemist Leroy Hood—who was then at the University of Washington—published a paper describing a genetically engineered strain of mouse that developed a lab-induced form of multiple sclerosis known as experimental autoimmune encephalomyelitis, or EAE.
When Hood's animals were housed at Caltech, they developed the disease. But, oddly, when the mice were shipped to a cleaner biotech facility—where their resident gut bacterial populations were reduced—they didn't get sick. The question was, why? At the time, Mazmanian says, "the authors speculated that some environmental component was modulating MS in these animals." Just what that environmental component was, however, remained a mystery for almost two decades.
But Mazmanian—whose laboratory examines the relationships between gut microbes, both harmful and helpful, and the immune systems of their mammalian hosts—had a hunch that intestinal bacteria were the key. "As we gained an appreciation for how profoundly the gut microbiota can affect the immune system, we decided to ask if symbiotic bacteria are the missing variable in these mice with MS," he says.
To find out, Mazmanian and his colleagues tried to induce MS in animals that were completely devoid of the microbes that normally inhabit the digestive system. "Lo and behold, these sterile animals did not get sick," he says.
Then the researchers decided to see what would happen if bacteria were reintroduced to the germ-free mice. But not just any bacteria. They inoculated mice with one specific organism, an unculturable bug from a group known as segmented filamentous bacteria. In prior studies, these bacteria had been shown to lead to intestinal inflammation and, more intriguingly, to induce in the gut the appearance of a particular immune-system cell known as Th17. Th17 cells are a type of T helper cell—cells that help activate and direct other immune system cells. Furthermore, Th17 cells induce the inflammatory cascade that leads to multiple sclerosis in animals.
"The question was, if this organism is inducing Th17 cells in the gut, will it be able to do so in the brain and central nervous system?" Mazmanian says. "Furthermore, with that one organism, can we restore to sterile animals the entire inflammatory response normally seen in animals with hundreds of species of gut bacteria?"
The answer? Yes on all counts. Giving the formerly germ-free mice a dose of one species of segmented filamentous bacteria induced Th17 not only in the gut but in the central nervous system and brain—and caused the formerly healthy mice to become ill with MS-like symptoms.
"It definitely shows that gut microbes have a strong role in MS, because the genetics of the animals were the same. In fact, everything was the same except for the presence of those otherwise benign bacteria, which are clearly playing a role in shaping the immune system," Mazmanian says. "This study shows for the first time that specific intestinal bacteria have a significant role in affecting the nervous system during MS—and they do so from the gut, an anatomical location very, very far from the brain."
Mazmanian and his colleagues don't, however, suggest that gut bacteria are the direct cause of multiple sclerosis, which is known to be genetically linked. Rather, the bacteria may be helping to shape the immune system's inflammatory response, thus creating conditions that could allow the disease to develop. Indeed, multiple sclerosis also has a strong environmental component; identical twins, who possess the same genome and share all of their genes, only have a 25 percent chance of sharing the disease. "We would like to suggest that gut bacteria may be the missing environmental component," he says.