Gut dysbiosis in anorexia nervosa patients

Anorexia nervosa (AN) is a devastating eating disorder in which a patient severely restricts food intake and may have purging behaviors. AN of course results in physical harm but there are also very significant psychosocial effects because of the disease. Studies have shown that the gut microbiome plays an important role in weight gain and it is therefore reasonable to believe that gut dysbiosis could be seen in individuals with anorexia nervosa.

Scientists in Japan characterized the microbiome of AN patients and compared them to healthy controls. They studied 25 women with AN and compared their microbiomes to 21 age-matched healthy females. They found that AN patients had a lower amount of total bacteria and specifically, lower amounts of C. coccoides group, C. leptum subgroup, B. fragilis, and Streptococcus.  

Several papers have shown the importance of gut bacteria on weight gain including those showing the impact that antibiotic use in poultry has on creating larger chickens. Other studies include those linking obesity to specific gut bacteria as well as studies that show transplantation of bacteria, specifically Christensenella minuta, reduced weight gain in mice.

These studies comprehensively show that there is some connection between gut bacteria and weight gain and therefore investigating it as a therapeutic mode for anorexia nervosa is logical. While this study was small in scale and no causal links can be made, it is important to understand that gut bacteria differs between AN patients and healthy controls. Microbiome therapies may be an option for treating anorexia nervosa.

Proton pump inhibitors affect the microbiome

Proton pump inhibitors (PPI) are used to reduce gastric acid production in individuals’ guts and are prescribed to treat ulcers, gastroesophogeal reflux disease (GERD), and other conditions associated with acid production. It is one of the most commonly used drugs in the world. We know (and have written about) that PPIs are associated with increased intestinal infections, specifically Clostridium difficile, and the gut microbiome plays an important role in infections of the intestine. A recent study looked at the influence that PPIs had on the gut microbiome.

The team of researchers studied the gut microbiome of 1815 individuals. They looked at PPI users vs non-users. Of those sampled, 215 of them were taking a PPI at the time that a sample was taken. It was found that those taking the PPIs had lower microbial diversity compared to those not taking PPIs. They also found that bacteria usually found in the mouth was over-represented in the fecal samples of those taking PPIs, including those in the Rothia genus. They also observed an increase in Enterococcus, Streptococcus, Staphylococcus, and Escherichia coli, a potentially pathogenic bacterium.

PPI usage effects are more prominent than those of most other drugs, including antibiotics. The results of this study are consistent with a less healthy microbiome and allow us to better understand why PPIs may lead to an increase of susceptibility to intestinal infections like C. diff.

The effect of various treatments for juvenile Crohn’s disease on the microbiome

CT scan showing Crohn's disease in the fundus of the stomach

Crohn’s disease is a type of inflammatory bowel disease that is characterized by an autoimmune response in the colon.  It is generally thought that the bacteria in the gut elicit this immune response and cause the disease.  In otherwords, Crohn’s is caused by a shift in the microbiome from a healthy state, to a dysbiotic one, although the ultimate cause of the disease is still unknown.  The standard of care for Crohn’s in adults is combinations of immunosuppressive drugs, although in children this is not normally recommended.  Instead, children take either a prescribed diet, normally something like Soylent that involves only essential nutrients, or antibiotics.  Scientists from UPenn recently monitored the microbiomes of children with Crohn’s that were put on various courses of treatment, as well as the progression of the disease.  They discovered the changes that occurred in the microbiome that yielded a therapeutic response, and many new associations between the microbiome and Crohn’s disease.  They published their results in Cell Host and Microbe.

The scientists measured the microbiomes and inflammatory markers of 90 children before and after entering therapy for Crohn’s: 52 taking anti-TNF (an immunosuppressant), 22 taking the enteral nutrition exclusively (i.e. something like soylent), and 16 taking the enteral nutrition along with any other food they wanted.  The scientists also took samples from 26 healthy children.  They discovered that of the 45 most abundant bacteria in each child, 14 were different between the Crohn’s children and the healthy children.  These included bacteria such as Prevotella and Odoribacter that were largely absent from the Crohn’s group, and Streptococcus, Klebsiella, and Lactobacillus that were in higher abundances in the diseased group.  Overall diversity was also higher in healthy patients compared to those with Crohn’s.  The researchers also discovered that high levels of fungi, such as Saccharomyces cerevisiae, in the stool were high associated with Crohn’s.  When the researchers monitored the response of Crohn’s patients to treatment they saw that in many patients the microbiome shifted rapidly to a healthier state, with less inflammation, within a week of treatment for all three therapies involved.

This study helped further define the dysbiosis that is associated with Crohn’s disease, as well as demonstrate how this dysbiosis is altered using treatment.  It was especially useful that treatment naïve children were used in the study, as many adult studies are unable to remove confounding variables of various previous courses of treatments.  IBD is a difficult disease to study because of its complexity, but this study supports the hypothesis that a dysbiosis is at the root of the problem.

We all emit our own 'microbial cloud'

Every individual has a microbiome compiled of millions of bacteria, fungi, viruses, and other microorganisms that is unique for each one of us. Whenever we travel to a new location and sit down or touch something, we are spreading our microbiome to that new location. A lot of research has gone into this phenomenon and is called the microbiome of the built environment. A new study out of the University of Oregon has expanded on this understanding and has described what they call a “microbial cloud”.

The scientists found that individuals not only spread their microbiome to new locations through direct contact but the microorganisms on our body are also dispersed into the air making up this microbial cloud. To better understand this, the scientists had 11 individuals sit in an enclosed room for 4 hours and they analyzed the DNA from the bacteria in the air. They found that when each individual sat in the room, there were thousands of bacteria in the room and everyone’s was distinct. They were able to identify specific characteristics of the people such as if it was a man or a woman.

The bacterial combinations found in the room could be linked back to specific individuals even after the person inhabited the room for only 4 hours. There were specific groups of bacteria like Streptococcus, often found in the mouth, as well as Propionibacterium and Corynebacterium, often found on the skin, that were most useful in identifying the individuals. While these bacteria were found around all the study participants it was the combination of bacteria that was key to identifying the individuals.

This finding could have several important applications. One often-discussed application of the microbiome is its use in forensic applications. It may be possible to use this ability to identify people and know if they were in a room or not to see if someone committed a crime, though it is not clear if it will be possible to identify people in a crowd of other individuals. Other applications include understanding the spread of infectious disease between individuals and within buildings. This is an exciting new development and I am certain we will see more research looking at our microbial clouds in the future.

The gut microbiome may be involved in Kawasaki Syndrome

Clinical manifestations and time course of Kawasaki disease

Kawasaki disease occurs in young children, and is characterized by long-lasting fever, coughing, diarrhea, along with other symptoms. What specifically causes this disease is unknown, but scientists guess it may be influenced genetically or by intestinal microbiota. Japan seems to have an unusually high rate of occurrence of KD. Researchers in Tokyo performed a longitudinal study of the intestinal microbiomes of KD patients, in order to look for any patterns that could suggest a relationship between intestinal microbiota and Kawasaki disease. The results have been published by Frontiers in Microbiology.

Fecal samples were collected from 28 Japanese children, ages ranging from 3 months to 9 years 6 months. Patients were both male (15) and female (13).  Fecal samples were collected twice from each child, for a total of 56 samples. The first (acute phase) sample was taken at the time of hospital admission, while the second (non-acute phase) was collected 4-6 months after the onset of Kawasaki disease. DNA was extracted from the fecal samples and sequenced to determine the bacterial composition of the intestines.

Roseburia species were found to be relatively abundant during the non-acute phase (4-6 months after disease onset). Species of Streptococcus were found mainly during the acute phase, such as S. pneumonia, orlais, pseudopneumoniae, mitis, gordonii, and sanguinis. This means there is a potential that these species of Streptococcus could be related to KD. To further determine if the Streptococcus species were related to KD, the researchers compared the species’ genomes to recent research in which they are involved, and found that Streptococcus could be a biomarker or pathogen for diseases with unknown causes, such as Kawasaki disease. While this is still a hypothesis and nothing is proven to be 100% true yet, it is definitely a topic that will be researched extensively in the nearby future. It may hold the key for understanding many other diseases whose causes are a mystery.