New research shows that Bifidobacteria transfer from mother to child

Both natural birth (as opposed to birth by C-section) and breastfeeding are topics that stir up a lot of conversation among mothers and the scientific community. For example, there is the question of whether breastfeeding rather than formula feeding has some specific benefit to an infant’s health. Well, what about the infant’s gut microbial health? A new article published by Applied and Environmental Microbiology takes a look at whether natural birth and breastfeeding coincides with an exchange of bacteria from mother to child.

Four mother and infant pairs were included in the study that was meant to discover whether the mother transfers any bacterial strains to the infant during vaginal birth and breastfeeding. In particular, the scientists were looking at the genus Bifidobacterium because this group has been known to be early colonizers of the infant gut. In addition, this genus has specific ways of digesting a human mother’s milk. Mother-infant pairs 2 and 4 exclusively breastfed, while pairs 1 and 3 supplemented with formula. Milk samples were collected from the mothers and fecal samples were collected from the mothers and children.

After sequencing the bacteria, B. adolescentis, B. angulatum, B. breve, B. dentitum, B. pseudolongum and B. thermacidophilum were found to be common between all of the mother and the infant fecal samples. The scientists then looked to see which bacteria were in both the mother’s milk and the infant’s fecal sample. The results suggest that the milk may be responsible for transferring B. adolescentis, B. angulatum, B. breve, B. longum and B. pseudolongum to the infant. Interestingly, there were also some bifidobacteria strains that were unique to the infant, suggesting that either they went undetected in the mother or that the infant was exposed to this bacteria from somewhere else.

After six months, samples were collected again in order to see how/if the sample compositions change. The scientists found that, especially in the infants, the abundance of bifidobacteria decreases. This is most likely due to changes in diet – less breastfeeding and more formula feeding – and perhaps environmental exposure. All in all, the results of this experiment shows that the infant microbiome might indeed be influenced by a vertical transfer of bacteria from mother to child. With more evidence of this as a possibility, science may begin looking into more complete analyses with larger study sizes.  

Microbiome differences between healthy people and those with IBS

Methane (above) is produced by Methanogens, which are increased in the guts of healthy individuals compared to those with diarrheal IBS.

IBS affects somewhere around 11% of all humans.  It is not known exactly what causes the disease but it is characterized by a low grade inflammation in the colon which can manifest itself as cramping, bloating, diarrhea, constipation, and overall abdominal discomfort.  Many scientists now believe this is a microbiome mediated disease that is caused by some sort of dysbiosis in the gut, unfortunately efforts to characterize exactly what differences occur in IBS individuals have not been successful.  A new article published last week in Nature Scientific Reports describes newly discovered differences in butyrate and methane producing bacteria in the guts of people with IBS.

The scientists sequenced the microbiomes of 66 healthy controls and 113 folks with IBS, at two time points 1 month apart.  They discovered that IBS patients had higher amounts of Bacteroides and lower levels of Firmicutes than healthy individuals, as well as an overall lower microbiome diversity.  In addition, there were no major changes to either group’s microbiomes over the one month measurement window.  Interestingly those people with diarrheal IBS had much lower levels of methanogens than healthy controls, and those people with constipation IBS had higher levels of methanogens than healthy controls.  Methanogens convert hydrogen gas to methane in the gut, and this study revealed a link between methane production and gastrointestinal (GI) transit time.  Finally, the researchers determined that diarrheal IBS patients also had much lower levels of known butyrate producers.  Butyrate, a short chained fatty acid (SCFA), is associated with improved GI permeability and overall GI health.

This study described a few important insights in IBS and the microbiome.  These insights, such as the metabolic differences between bacteria in healthy individuals and those with IBS may be important to future therapeutics to treat this disease.  For example, perhaps folks with IBS could eat a lot of fiber and in the hopes of increasing the amount of butyrate in their guts.  Of course, the observed difference is only an association at this point, but other studies have suggested an increase in fiber can help relieve symptoms of the disease. 

Gastric bypass surgery alters microbiome which possible contributes to weight loss

Schematic of Roux-en-Y anastomosis.

Roux-en-Y gastric bypass surgery and vertical banded gastroplasty are two types of bariatric weight loss surgeries that are highly effective in promoting weight loss.  The mechanisms for their efficacy are complex and not completely known, but both surgeries are shown to reduce caloric intake, suppress hunger and increase gastric emptying.  Little is known about how the microbiome changes during these surgeries, and how this change may effect subsequent weight loss.  A team of Swedish scientists investigated this topic and showed the gut microbiota undergo important changes.  They published their results in the journal Cell Metabolism.

The researchers compared the microbiomes of women that were obese and hadn’t had surgery with those who were of similar BMI presurgery, but had undergone surgery at least nine years earlier.  They observed some major differences in the women’s microbiomes, with the post-operative women had much higher levels of Gammaproteobacteria and lower levels of Firmicutes.  When the scientists looked at actual genetic variations they found many differences.  Some notable differences were a decrease in short chain fatty acid (SCFA) and in increase in trimethylamine N-oxide (TMAO) creation in women who had surgery.  As we have written about in this blog before, SCFAs are often associated with health, while TMAO is a risk factor for some cardiovascular diseases.  Interestingly, when they took the microbiomes from both groups of women and transferred them into germ-free mice, the mice receiving microbiomes of women that had undergone surgery gained less weight than the mice that received microbiomes of obese women.

Gastric bypass surgery is often a last resort for folks that have severe obesity.  While not normally considered, the microbiome is drastically affected by this procedure. The microbiome is certainly altered by the procedure, and it appears that it may even be helping keep the weight off.  However, there may be some negative microbiome-mediated consequences as well, derived from alterations to micrbiome metabolism, such as an increased level of TMAO.  Like all surgeries, folks undergoing this one need to balance the risks and rewards of the procedure, and hopefully after this study, the microbiome will be considered.

Early life stress implications on the gut microbiome

A growing body of evidence supports the significance of the gut microbiome with respect to behavioral disorders, as mediated by disruption to the gut-brain axis.  Importantly, there is a lack of understanding regarding associations between gut microbiome dysbiosis and behavioral phenotypic outcome.  Traumatic childhood events early-in-life can result in later-in-life behavioral consequences.  Maternal separation (MS) is an example of such an event that is represented with a well-established preclinical (i.e., animals) experimental model for early life stress.  In a recent study, researcher’s sought to investigate the precise role of MS in the induction of changes to the gut microbiomes of mice, and the potential behavior phenotypic consequences brought on by these changes. 

C57 mice were subject to three unique experimental groups: germ-free (GF) mice, specific pathogen-free mice (SPF, i.e. mice with microbiome compositions), and germ-free mice that were eventually subject to recolonization.  Mice were either left alone after birth or exposed to MS 3 days after birth.  Behavior was examined after 8 weeks, and the germ-free group was sacrificed after 9-10 weeks and the SPF group after 16-20 weeks.  The recolonization group was recolonized with microbiota at 12-13 weeks, followed by more behavioral tests and subsequent sacrificed. 

Corticosterone - a major stress hormone - was significantly elevated in both GF and SPF mice that were subjected to MS.  The researchers next wanted to define a relationship between the host microbiome and anxiety-like behaviors weeks after being separated from the mothers.  It was fist observed that MS did indeed alter microbiota composition in SPF mice.  Interestingly, MS-induced anxiety like behavior was observed in SPF mice, but not in GF mice, suggesting that the microbiome played a significant role in the development of these types of behaviors.  The experimenters then recolonized the guts of a subgroup of GF mice.  Indeed, behavior was altered in MS mice whose guts were colonized as compared to the MS mice that remained germ free.  Other physiological indicators demonstrated significant interactions between MS and the presence of gut microbiota, as gut microbiota presence had a significant impact on noradrenaline and serotonin levels. 

All told, the findings in this study suggest microbiome dysbiosis is a critical physiological driving force behind the behavioral phenotypes associated with early life stress events.  It will next be important to begin thinking about translate these preclinical findings in a clinical setting, in hopes of exploring ways to help those in need.

Microbiome of rheumatoid arthritis patients is altered and partially restored after treatment

A recent study found that the oral and gut microbiome were altered in patients with rheumatoid arthritis (RA). RA is an inflammatory disease that generally affects the joints in one’s hand and feet and can eventually cause bone erosion and deformity. RA occurs when a person’s immune system attacks it’s own tissues and can be implicated in other parts of the body as well.

In the study published in Nature Medicine, the scientists sequenced fecal samples of 212 individuals. This 212 sample included 77 people with RA not undergoing treatment, 80 healthy participants unrelated to people in the study,17 RA patients as well as17 healthy relatives to match the 17 RA patients and finally, 21 patients with RA undergoing treatment with disease-modifying anti-rheumatic drugs (DMARDs). They also took dental and saliva samples from individuals with and without RA.

They found that the bacterial composition of RA patients differed from patients without RA however the patients undergoing DMARDs had microbiomes that more closely resembled the healthy control subjects. This was important because it provides support to the theory that RA is a disease that may be brought about or affected by pathogenic bacteria or a lack of other specific bacteria.

This result may be a step forward toward the development of therapeutics targeting the microbiome of individuals of RA. It also may be possible to better diagnose or even determine the prognosis of RA patients by studying their microbiome. Further work will be needed with larger patient populations but this is a positive development for treating and studying RA using the microbiome. 

HIV vaccine failed because of interaction with microbiome

Scanning electron micrograph of HIV-1, colored green, on a lymphocyte.

From 2009 to 2013, scientists at Duke University and the National Institute of Allergy and Infectious Diseases had been working on what looked like a promising cure to HIV. The study was terminated in 2013 because it was clear that the vaccine was not effective in protecting against HIV infection. An article recently published by Science Magazine gave insight into why the HIV vaccine unfortunately failed. Hint: it has something to do with the microbiome.

The vaccine was administered in the study to adult males in the form of an initial vaccine as well as a second booster vaccine. The HIV vaccine looked promising because it stimulated the body’s immune system to produce antibodies that recognize HIV. The unexpected result, however, was that these antibodies also recognized bacteria like Escherichia coli, a very important bacteria that lives in the human gut. It should be easy to see why this is a bad thing for the microbiome. Destroying important gut bacteria is very detrimental to humans, which we see over and over again here on the blog. Additionally, because the antibodies were reactive to bacteria as well as the HIV virus, it took away from the effectiveness of fighting HIV.

This study is very important in the search towards finding a cure to HIV, because it presented an unexpected obstacle that a lot can be learned from. Moving forward, questions are already being raised by the scientists such as, would this vaccine work for children if immunization was given to pregnant mothers? Perhaps the still-developing immune system would better be able to work with the vaccine. Only more research can prove whether the HIV vaccine is indeed still promising.  In addition, this may provide insights into the efficacy of vaccines for other diseases.  Perhaps the microbiome plays a large role in their effectiveness.  Vaccine research going forward should begin to take the microbiome into account.