Patients With Irritable Bowel Syndrome Have High Rates of Fibromyalgia

By Pat Anson, PNN Editor

A large new study has found high rates of fibromyalgia in patients with irritable bowel syndrome (IBS), adding to a growing body of evidence linking gut bacteria to chronic pain disorders. IBS patients were also more likely to have chronic fatigue syndrome (CFS).

The study, recently published in the journal Biomedicines, looked at more than 1.2 million IBS patients hospitalized in the U.S. over a three-year period. They found that the prevalence rate of fibromyalgia in the IBS patients was 10.7 percent, about five times higher than the fibromyalgia rate (1.4%) in the general adult population.

Fibromyalgia is a poorly understood condition characterized by widespread body pain, headaches, fatigue, insomnia and mood disorders; while IBS causes abdominal pain, cramps, bloating, gas and diarrhea. Gut bacteria has been associated with both IBS and fibromyalgia, but the exact mechanism of action remains unclear.

“This is yet another example where ailments in the gut are linked to ailments elsewhere in the body and mind,” said senior author Yezaz Ghouri, MD, an assistant professor of clinical medicine and gastroenterology at the University of Missouri School of Medicine. “As we continue to learn more about how gut health effects health elsewhere it is important that clinicians look for and manage somatic comorbidities in IBS patients.”

Fibromyalgia and CFS are known as “somatic” disorders because patients who have them often experience anxiety and depression – a tendency perhaps explained about the lack of effective treatments for their physical symptoms.

“Because IBS patients have higher prevalence of somatic comorbidities such as fibromyalgia and chronic fatigue syndrome, identifying and treating these disorders can improve their quality of life,” said lead researcher Zahid Ijaz Tarar, MD, a fellow in the division of gastroenterology and hepatology at the University of Missouri School of Medicine.

“Earlier identification of comorbidities is valuable to inform treatment strategies, including consulting other specialties such as rheumatology and psychiatry to improve the overall health outcomes in IBS patients.”

In addition to fibromyalgia, the research team found that hospitalized IBS patients were also significantly more likely to be white and female.  Less than one percent (0.42%) had a CFS diagnosis – a small percentage to be sure, but still higher than CFS rates in the general population (0.06%).

The high rates of fibromyalgia and CFS in IBS patients has led to speculation that poor diets or antibiotics may cause an imbalance of “bad” bacteria in the gastrointestinal system, allowing toxins to leak into the bloodstream and cause other health problems.

A recent study found that Klebsiella aerogenes, a bacterium that causes white blood cells to produce excess amounts of histamine, can trigger a painful immune system response.

Another study found that women with fibromyalgia have strikingly different types and amounts of bacteria than those without fibromyalgia. Faecalibacterium prausnitzii, a “good” bacterium that is normally abundant in the human gut, was found to be depleted in fibromyalgia patients. Other bacteria associated with IBS, CFS and interstitial cystitis were found to be abundant in fibromyalgia patients, but not in the healthy control group.  

Lyme Disease: How a Bacteria Plays Havoc with Immune Systems

By Dr. Jenny Wachter, University of Saskatchewan

Lyme disease is the leading vector-borne disease — meaning diseases that are transmitted to humans from another organism like a tick or mosquito — in North America and Europe.

New human cases are estimated at over 400,000 in the United States each year. Canada has experienced a drastic increase in human cases, from 266 cases in 2011 to 3,147 in 2021, as the habitat of its vector, a tick, expands north.

The initial symptoms of human Lyme disease can be vague, such as fever, headache, fatigue and often rash. It is a potentially serious condition that can affect multiple systems in the body — including the heart, nervous system and joints — and can become a chronic illness.

Lyme disease is caused by a unique, spiral-shaped (spirochete) bacterium called Borrelia burgdorferi. B. burgdorferi cannot survive in the environment on its own. For survival and transmission, it requires susceptible hosts (usually small mammals or birds) and a specific vector: the black-legged tick, also called the deer tick.

Evading the Immune System

B. burgdorferi must survive extremely diverse conditions over the course of its transmission and infection cycle: from host to tick vector, and then into new hosts.

This bacterium senses and responds to its surroundings, most notably by modifying its appearance by changing the proteins on its outer surface to help it survive in either the tick or the host.

When a tick infected by B. burgdorferi bites and feeds on a vertebrate host, it provides a signal for the bacteria to switch its proteins to those required to infect the host, and to begin migrating through the tick and into the bite site. This process takes between 36 and 72 hours.

However, many of these proteins are recognized by the host as foreign, and the host’s immune system works to try to clear the infection. This includes a strong, antibody response targeted against B. burgdorferi.

Despite these immune responses, B. burgdorferi is able to cause long-term infections. In natural host reservoirs — the animals that the bacterium usually finds itself in via tick bites, such as small rodents — these infections do not cause diseases like those seen in humans and other non-natural reservoirs.

In fact, the bacteria itself does not produce any products that would be toxic to its hosts, either natural or non-natural. Yet chronic infection in humans can lead to Lyme neuroborreliosis, carditis and Lyme arthritis.

How then, are these bacteria able to cause such a devastating disease in humans and other animals, but not in their natural host reservoirs?

While there is still much to learn about B. burgdorferi, we know of several factors that play a role in the range of disease it causes. These include:

• its genetic make-up,

• its ability to access various tissues (such as the joints, heart and nervous system) due to its ability to move around (motility), and

• the immune response of the host.

Apart from motility, B. burgdorferi also protects itself from the strong B. burgdorferi-specific targeted antibody response of its host’s immune system by changing the appearance of the main outer surface protein expressed during persistent infection in a process called antigenic variation.

In addition to antigenic variation, B. burgdorferi bacteria can also change their DNA by exchanging genetic information, a process also known as gene transfer. This process allows these bacteria to further alter their appearance during infection to avoid the host immune system.

This process works so well that these B. burgdorferi bacteria appear different enough to allow re-infection or even co-infection (where multiple strains of B. burgdorferi infect a single host at the same time) of a vertebrate host, like a mouse or a human, despite the presence of specific antibodies to fight the bacterium.

In fact, in nature, the majority of host reservoirs and the ticks that carry the bacterium are infected with multiple strains of B. burgdorferi. The ability of B. burgdorferi to reinfect and co-infect both ticks and hosts increases the spread of the bacteria in the environment as well as the chances that humans will encounter Lyme disease.

Human Cases of Lyme Disease Are Increasing

As a vector-borne pathogen, B. burgdorferi only infects individuals that are bitten by an infected tick. It is not transmitted from person to person.

Environments that support black-legged/deer ticks are at risk of harbouring B. burgdorferi. In North America, these species of ticks are widely distributed throughout the eastern and midwestern United States. Recent geographic expansion to the north is increasing the prevalence of Lyme disease in Canada.

The increase of human Lyme disease cases highlights the failure of existing preventive strategies — such as minimizing exposure to tick habitats, performing diligent tick checks, and wearing suitable clothing when performing activities in known tick habitats — and emphasizes the need for an effective human vaccine.

At Vaccine and Infectious Disease Organization at the University of Saskatchewan, we are taking a One Health approach by recognizing that human health is closely related to the health of animals and the shared environment. We are investigating the role of B. burgdorferi, ticks, and susceptible animals on the spread and survival of the Lyme disease bacterium.

It is important to mimic the natural infectious cycle as much as possible when identifying potential vaccine and drug targets. This is because the way host animals are infected (for example, artificial needle infection or natural tick bite) can produce drastic differences in the resulting infection.

Additionally, despite the prevalence of this disease, there are still many aspects of the infectious cycle that remain unknown due to the uniqueness of B. burgdorferi and a lack of knowledge about the tick vector.

For example, we recently learned that a B. burgdorferi protein is responsible for regulating the components necessary for the bacterium to infect vertebrates, including humans. The absence of this protein, among other things, leads to the death of B. burgdorferi in ticks, making it an exciting target for research investigation.

By learning more about the molecular mechanisms that change or reduce the severity of the disease caused by this bacterium, we can identify new targets for the prevention of human Lyme disease. 

Jenny Wachter, PhD, is a research scientist and adjunct professor at University of Saskatchewan.

This article originally appeared in The Conversation and is republished with permission.

Newly Discovered Gut Bacteria Linked to Rheumatoid Arthritis

By Meagan Chriswell, University of Colorado Medicine

Rheumatoid arthritis affects 1 in 100 people worldwide. It causes inflamed, painful and swollen joints, often in the hands and wrists, and can lead to loss of joint function as well as chronic pain and joint deformities and damage. What causes this condition has been unknown.

In our recently published study, my colleagues and I found an important clue to a potential culprit behind this disease: the bacteria in your gut.

Rheumatoid arthritis is an autoimmune condition, meaning it develops when the body’s immune system starts to attack itself. Proteins called antibodies, which usually help fight off viruses and bacteria, begin to attack the joints instead.

The origins of the antibodies that cause rheumatoid arthritis have been an area of study for many years. Some research has shown that these antibodies can start forming at sites like the mouth, lung and intestines over 10 years before symptoms arise. But until now, it was unclear why researchers were finding these antibodies in these particular areas.

We wanted to investigate what could trigger the formation of these antibodies. Specifically, we wondered if bacteria in the microbiome, a community of microorganisms that live in the intestines, might be the ones activating the immune response that leads to rheumatoid arthritis.

Since microbes commonly live at the same sites as the antibodies driving rheumatoid arthritis, we hypothesized that these bacteria could be triggering the production of these antibodies. We reasoned that though these antibodies were meant to attack the bacteria, rheumatoid arthritis develops when they spread beyond the intestines to attack the joints.

First, we sought to identify the intestinal bacteria targeted by these antibodies. To do this, we exposed the bacteria in the feces of a subset of people at risk for developing rheumatoid arthritis to these antibodies, allowing us to isolate just the bacterial species that reacted and bound to the antibodies.

We found that one previously unknown species of bacteria was present in the intestines of around 20% of people who were either diagnosed with rheumatoid arthritis or produce the antibodies that cause the disease.

As a member of the Cherokee Nation of Oklahoma, I suggested we name this species Subdoligranulum didolesgii (“didolesgii” means arthritis or rheumatism in Cherokee) as a nod to the contributions that other Indigenous scholars have made to science as well as the fact that rheumatoid arthritis affects Indigenous people at a higher rate than other populations.

Subdoligranulum didolesgii has not been detected in the feces of healthy people before, and it is currently unknown how prevalent this bacteria is in the general population.

We also found that these bacteria can activate specialized immune cells called T cells in people with rheumatoid arthritis. T cells drive inflammatory responses in the body, and have been linked to the development of different autoimmune diseases.

These findings suggest that these gut bacteria may be activating the immune systems of people with rheumatoid arthritis. But instead of attacking the bacteria, their immune system attacks the joints.

Why This Bacteria?

It is still unknown why people with rheumatoid arthritis develop an immune response to Subdoligranulum didolesgii. But we think it may be the culprit when it comes to rheumatoid arthritis because this bacteria is found only in the intestines of people with rheumatoid arthritis, and not in the intestines of healthy people.

While many immune responses happen in the intestines, they are usually self-contained and do not spread to other areas of the body. However, we believe that a particularly strong intestinal immune response against Subdoligranulum didolesgii could allow antibodies to bypass the intestinal “firewall” and spread to the joints.

To confirm our hypothesis, we gave mice an oral dose of Subdoligranulum didolesgii and monitored their reaction. Within 14 days, the mice began to develop joint swelling and antibodies that attacked their joints.

My colleagues and I hope this research can shed light on the origins of rheumatoid arthritis. Our next goal is to discover how common these bacteria are in the general population and test whether the presence of these bacteria in the gut may lead to the development of rheumatoid arthritis in people.

It’s important to note that antibiotics are unlikely to be helpful treatment for the microbiomes of patients with rheumatoid arthritis. Although Subdoligranulum didolesgii may be triggering an autoimmune response for some people with rheumatoid arthritis, antibiotics eliminate both helpful and harmful bacteria in the gut. Additionally, removing the bacteria won’t necessarily stop the immune system from attacking the joints once it has started.

Nevertheless, we believe that these bacteria can be used as tools to develop treatments for rheumatoid arthritis and hopefully ways to prevent disease from happening in the first place.

Meagan Chriswell is a MD/PhD Candidate in Immunology at the University of Colorado Anschutz Medical Campus. She does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article.

This article originally appeared in The Conversation and is republished with permission.

Gut Bacteria Identified as Cause of IBS

By Pat Anson, PNN Editor

Canadian researchers have identified one of the primary causes of Irritable Bowel Syndrome (IBS), a frustrating intestinal condition that causes abdominal pain, cramps, bloating, gas and diarrhea.

The culprit appears to be Klebsiella aerogenes, a strain of bacteria that causes white blood cells to produce excess amounts of histamine, a chemical that triggers a painful immune system response. Gut bacteria have long been suspected as a likely cause of IBS, but this is the first time a specific bacterial strain has been identified.  

Researchers at McMaster University and Queen’s University studied stool samples from both Canadian and American IBS patients, and found Klebsiella aerogenes in about 25 percent of them.

“We followed up these patients for several months and found high levels of stool histamine at the time when the patients reported severe pain, and low stool histamine when they were pain-free,” said senior author Premysl Bercik, MD, a gastroenterologist and professor at McMaster’s Michael G. DeGroote School of Medicine.

Further tests on laboratory mice that were colonized with gut microbes from IBS patients showed that several types of bacteria produced histamine, but Klebsiella aerogenes was a “super-producer.” The chemical is produced when histidine, an essential amino acid in animal and plant protein, is converted into histamine, triggering pain and inflammation.

“Now that we know how the histamine is produced in the gut, we can identify and develop therapies that target the histamine producing bacteria,” said first author Giada de Palma, an assistant professor of medicine at McMaster.

Researchers found that when mice colonized with histamine producing bacteria were fed a diet low in carbohydrates, histamine production dramatically decreased. That would explain the benefits of diets low in carbohydrates and high in dietary fiber, which are often recommended to IBS patients. Allergy medications that block histamine production may also be useful in treating IBS.

“Many but not all IBS patients will benefit from therapies targeting this histamine driven pathway,” said co-first author David Reed, assistant professor of medicine at Queen’s University.

The McMaster-Queens study was funded by the Canadian Institutes of Health Research and published in the journal Science Translational Medicine.

Exercise Reduces Pain by Increasing Beneficial Bacteria

By Pat Anson, PNN Editor

Regular exercise can benefit people in many different ways, helping us lose weight, reduce the risk of heart disease, and boosting overall health.  

But researchers at the University of Nottingham have found that exercise has an unexpected benefit for people with arthritis. Regular exercise increases levels of beneficial bacteria in their digestive tracts, which reduces pain and inflammation by increasing levels of endocannabinoids – cannabis-like substances naturally produced by the body.

The study, published in the journal Gut Microbes, is believed to be the first to find a potential link between endocannabinoids, exercise and gut microbes.

"Our study clearly shows that exercise increases the body's own cannabis-type substances. Which can have a positive impact on many conditions,” says lead author Amrita Vijay, a Research Fellow at Nottingham’s School of Medicine. "As interest in cannabidiol oil and other supplements increases, it is important to know that simple lifestyle interventions like exercise can modulate endocannabinoids."

Vijay and her colleagues enrolled 78 people in their study. Half of the participants did 15 minutes of muscle strengthening exercises every day for six weeks, and the rest did nothing. Blood and fecal samples were collected from both groups.

At the end of the study, participants who exercised not only had lower pain levels, they also had significantly more Bifidobacteria and Coprococcus 3 -- bacteria that produce anti-inflammatory substances and lower levels of cytokines, which regulate inflammation.

These gut bacteria were particularly adept at raising levels of short chain fatty acids (SCFAs), which increase levels of endocannabinoids. About a third of the anti-inflammatory effects of the gut microbes was due to their ability to raise endocannabinoid levels.

Importantly, the exercise group also had lower levels of Collinsella – a bacteria known to increase inflammation that is strongly associated with processed food and diets low in vegetables.    

“In this study we show that circulating levels of ECs (endocannabinoids) are consistently associated with higher levels of SCFAs, with higher microbiome diversity and with lower levels of the pro-inflammatory genus Collinsella. We also show statistically that the anti-inflammatory effects of SCFAs are up to one third mediated by the EC system,” researchers concluded.

Previous studies have also found an association between gut bacteria and painful conditions. A 2019 study at McGill University found that women with fibromyalgia had 19 different species of bacteria that were present in either greater or lesser quantities than a healthy control group.

Bacteria associated with irritable bowel syndrome, chronic fatigue syndrome and interstitial cystitis were also found to be abundant in the fibromyalgia patients, but not in the control group.    

Having a healthy diet can also affect pain levels for migraine, neuropathy and other types of chronic pain. A recent study funded by the National Institutes of Health found that migraine sufferers who ate more fatty fish and reduced their consumption of polyunsaturated vegetable oils — frequently found in processed foods — had fewer headaches.

Can a Junk Food Diet Cause Osteoarthritis?

By Steve Weakley

Does what’s in your gut influence the pain in your knees? New research on mice at the University of Rochester Medical School suggests that it might, but the results are far from conclusive.

Researchers fed one group of laboratory mice a high fat diet that included red meat and milkshakes, and another group of mice a healthier low-fat diet. Both groups of mice had their knees surgically damaged to mimic the effects of osteoarthritis -- “wear and tear” arthritis that is often associated with age, obesity or injury.

Twelve weeks of the high fat diet made the mice obese and diabetic and led to more seriously damaged joints. It also created an imbalance of harmful bacteria in their digestive tracts. 

One group of the fat mice were then given a supplement containing the prebiotic fiber oligofructose (also available as an over-the-counter probiotic).  The researchers said the supplement did not cause the mice to lose weight, but it did greatly improve their blood sugar levels and the balance of healthy bacteria in their gut.  More importantly, the study concludes, the mice that were given the supplement also had healthier joints than the control group.

The University of Rochester study concluded that prebiotics and the correction of gut bacteria might help protect against osteoarthritis caused by obesity. And one of the researchers, Dr. Robert Mooney, told Forbes that the study suggests osteoarthritis may be accelerated or even caused by inflammation.

"That reinforces the idea that osteoarthritis is another secondary complication of obesity--just like diabetes, heart disease, and stroke, which all have inflammation as part of their cause," said Mooney. "Perhaps, they all share a similar root, and the microbiome (digestive bacteria) might be that common root."

However a critique by Britain’s National Health Service (NHS) said that conclusion might be premature.

“It's presumptuous to conclude that an imbalance of gut bacteria could be directly linked to risk of osteoarthritis in humans from the results of a study in mice with artificially induced knee damage. As such, there's no compelling evidence that prebiotics would prevent or reverse osteoarthritis,” the NHS said.

“Aiming for a healthy weight through a good diet combined with physical activity is a better strategy for reducing the risk of osteoarthritis (as well as many other long-term conditions) than taking prebiotics to try to combat the effects of a poor diet. “

Osteoarthritis is a joint disorder that leads to progressive joint damage. It can affect any joint in the body but is most commonly felt in weight bearing joints such as the knees and hips. Nearly 40 percent of Americans over the age of 45 have some degree of knee osteoarthritis.

Previous studies have also found a link between a high fat diet and osteoarthritis.  Australian researchers reported last year that a diet rich in animal fats, butter and palm oil weakens cartilage and produces osteoarthritis-like changes in the knee.

"We also found changes in the bone under the cartilage on a diet rich in saturated fat," said Professor Yin Xiao of Queensland University of Technology’s Institute of Health and Biomedical Innovation. "Our findings suggest that it's not wear and tear but diet that has a lot to do with the onset of osteoarthritis.”

The University of Rochester researchers hope to include humans in future studies on the effects of diet on osteoarthritis.

Bacteria Studies Give New Hope to IBD Patients

By Pat Anson, Editor

A new study is adding to the growing body of evidence linking gut bacteria to autoimmune and gastrointestinal diseases – research that could lead to new and more effective treatments.

Researchers at the University of Utah used animal studies to show that a certain type of yeast can aggravate symptoms of Inflammatory Bowel Disease (IBD). Their findings, published in the journal Science Translational Medicine, also suggest that allopurinol, a generic drug already on the market, could offer some relief.

IBD is an autoimmune disease characterized by chronic inflammation of the gastrointestinal tract, causing diarrhea, pain, fatigue and weight loss.

For years doctors have used the presence of yeast antibodies, specifically antibodies in the yeast Saccharomyces cerevisiae, to differentiate between Crohn’s disease and ulcerative colitis, two variations of IBD. But it was unclear the role that yeast played in relation to IBD.

“To me this was a huge hole in our understanding of the role of yeast in IBD and our health,” said June Round, PhD, an associate professor in pathology at the University of Utah School of Medicine.

Round and her research team studied two types of yeast that are common in healthy people and IBD patients. Saccharomyces cerevisiae, also called Baker’s yeast, is a prominent organism in the environment and in our food. Rhodotorula aurantiaca is also commonly found in the environment, as well as milk and fruit juice.

Scientists gave each type of yeast to laboratory mice that had been treated with chemicals to induce IBD-like symptoms. The symptoms worsened in mice fed S. cerevisiae, but not in those fed R aurantiaca.

“The mice fed S. cerevisiae experienced significant weight loss, diarrhea, bloody stool, just like a person with IBD,” said Tyson Chiaro, graduate student in Round’s lab.

Further study revealed that the mice fed S. cerevisiae had a higher concentration of nitrogen-rich compounds, called purines, than the mice fed R. aurantiaca. Unlike other yeasts, S. cerevisiae cannot break down purines that accumulate in the intestinal tract and produce uric acid. Uric acid exacerbates inflammation, which may worsen IBD symptoms.

When the mice were treated with allopurinol, a medication used to block the production of uric acid in gout patients, the drug significantly reduced their intestinal inflammation.

“Our work suggests that if we can block the mechanism leading to the production of uric acid, perhaps with allopurinol, IBD patients with a high concentration of S. cerevisiae antibodies may have a new treatment option to reduce inflammation, which could allow the intestine time to heal,” said Round.

E. Coli linked to IBD and spondyloarthritis

Another recent study has helped researchers identify E. coli bacteria found in people with Crohn's disease that can trigger inflammation associated with spondyloarthritis, a painful arthritic condition that affects the spine and joints.

Researchers used fecal samples from IBD patients to identify bacteria in the gut that were coated with antibodies called immunoglobulin-A (IgA) that fight infection. Using flow cytometry, in which fluorescent probes are used to detect IgA-coated bacteria, the researchers found the E. coli bacteria were abundant in fecal samples from patients with both Crohn's disease and spondyloarthritis.

"Our findings may allow us to develop diagnostic tools to stratify Crohn's patients with spondyloarthritis symptoms as well as patients at risk," said senior author Dr. Randy Longman, an assistant professor of medicine and director of the Jill Roberts Institute Longman Lab at Weill Cornell Medicine.

Longman and his research team found that patients with Crohn's disease and spondyloarthritis had high levels of Th17 cells, which help fight inflammation. The finding may help physicians select therapies that target inflammation in both the bowels and the joints.

"We knew there was smoke but we didn't know where the fire was," said Dr. Kenneth Simpson, a professor of small animal medicine at Cornell's College of Veterinary Medicine. "If we can block the ability of bacteria to induce inflammation, we may be able to kick Crohn's disease and spondyloarthritis into remission."

The study findings are also published in Science Translational Medicine

Can Gum Disease Cause Rheumatoid Arthritis?

By Pat Anson, Editor

Scientists have long suspected that pathogens and bacterial infections may play a role in the development of autoimmune diseases such as rheumatoid arthritis (RA). Now there is evidence that a bacterium associated with chronic gum infections may trigger an inflammatory response characteristic of RA, a discovery that could lead to new ways to treat and prevent the disease.

"This research may be the closest we've come to uncovering the root cause of RA," said Maximilian Konig, MD, a former Johns Hopkins University School of Medicine fellow now at Massachusetts General Hospital.

Rheumatoid arthritis is a chronic autoimmune disease in which the body’s own defenses attack joint tissues, causing pain, inflammation and bone erosion. About 1.5 million Americans and one percent of adults worldwide suffer from RA. There is no cure for the disease and treatments only focus on slowing its progression.

In a study of nearly 200 RA patients, Konig and his colleagues found that nearly half had antibodies against Aggregatibacter actinomycetemcomitans in their blood.  

The level of infection with the bacteria was similar in patients with periodontal (gum) disease, but quite different in healthy patients, only 11 percent of whom tested positive for A. actinomycetemcomitans.

An infection with A. actinomycetemcomitans appears to induce the production of citrullinated proteins, which are suspected of activating the immune system and driving the cascade of events leading to RA.

"This is like putting together the last few pieces of a complicated jigsaw puzzle that has been worked on for many years," says Felipe Andrade, MD, a senior study investigator and associate professor of Medicine at the Johns Hopkins University School of Medicine.

Andrade cautions that over half of the study participants with RA had no evidence of an infection with A. actinomycetemcomitans, which may indicate that other bacteria in the gut, lung or elsewhere could be involved. He says more research is needed to determine if there is a cause and effect relationship between bacteria and RA.

"If we know more about the evolution of both combined, perhaps we could prevent rather than just intervene," he said.

The Johns Hopkins study is published in the journal Science Translational Medicine.

Scientists have observed an association between periodontal disease and RA since the early 1900s, and have suspected that both diseases may be triggered by a common factor. In the last decade, studies have focused on a bacterium known as Porphyromonas gingivalis, which is found in patients with gum disease. However, research has so far failed to corroborate such a link.

Researchers in the current study found inflammation in the joints of RA patients that was similar to the inflamed gums of patients with periodontal disease, an inflammatory process known as hyper-citrullination.

Citrullination occurs naturally in everyone as a way to regulate the function of proteins. But in people with RA, the process becomes hyperactive, resulting in the abnormal accumulation of citrullinated proteins. This drives the production of antibodies against proteins that create inflammation and attack a person's own tissues, the hallmark of RA.