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Clinical trial for probiotics in irritable bowel syndrome fails to show efficacy

Irritable bowel syndrome is the most common functional gastrointestinal disorder, affecting about 10-15% of people in the United States alone, according to the International Foundation for Functional Gastrointestinal Disorders website. Fortunately, as described by the IFFGD, IBS is a functional disorder, meaning that while it does affect quality of life, it does not affect life expectancy. Probiotics have been studied as treatment for IBS because, as we’ve seen in many other examples of probiotic use, it is safe and rarely has any negative effects on the consumer. Some trials have shown that probiotics help relieve the symptoms of IBS; however the conclusions are controversial due to study structure and participant numbers. For this reason, scientists in Seoul, South Korea recently published a study in the Journal of Clinical Biochemistry and Nutrition, which studied the effects of a multi-species probiotic mixture on IBS symptoms using a double-blind study with a large number of participants.

Eighty-one patients participated in the 4-week-long double-blind study, with 42 people receiving a multi-species probiotic (containing Lactobacilli, Bifidobacteria, and Streptococci) and 38 people receiving a placebo. Baseline fecal samples were collected before probiotic/placebo consumption, revealing no significant difference between the two groups of participants. After consumption, the probiotic group showed a significant increase in concentrations of the probiotic bacterial strains in fecal samples, but not significant increase of levels of Bacteroidetes and Firmicutes.

In terms of symptom relief, while the probiotic group reported a greater percentage of relief, it was not significantly greater than the placebo group. This could be a classic case of the placebo effect, which is a phenomenon in which a sham treatment can actually improve symptoms because the person receiving the placebo believes it will help them. The results of this study are not concrete because there was no significant difference in symptom improvement; however there were significant increases in probiotic strains in fecal samples of the probiotic group. This study could be a step in the right direction toward relieving IBS symptoms.

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The views expressed in the blog are solely those of the author of the blog and not necessarily the American Microbiome Institute or any of our scientists, sponsors, donors, or affiliates.

The giant panda’s microbiome isn’t doing it any favors

Panda bears are quite unique in the animal kingdom because they are nearly strictly herbivores yet they are descended from omnivores.  In fact, scientists aren’t quite sure why panda’s made the transition to eating bamboo, because it is a relatively inefficient energy source.  Making matters worse for the panda, its gastrointestinal tract is rather short, and resembles other carnivores, whereas most herbivores have very long gastrointestinal tracts that allow for long retention times for the microbiome to do its work.  This microbiome, of course, breaks down plant material into usable sources of energy for the host and it is critical in all herbivores.  Scientists from China recently investigated the panda’s microbiome, and to their surprise discovered that it too, resembled carnivores’ microbiomes, rather than herbivores’ as one might expect.  They published their results last week in MBio.

The scientists measured the fecal microbiomes of 45 captive pandas over the course of one year, including cubs, juveniles, and adults.  They then compared these microbiome samples with previously reported microbiomes of 54 other species, and wild, rather than captive pandas.  Their first discovery was that the panda’s microbiome was not as diverse as many of these other species, and as our regular readers know, low diversity has been implicated in many diseases in humans.  Next, they found that the panda’s microbiome was actually much more similar to other carnivorous species, especially other bears and tigers, than herbivorous species, and was dominated in Escherichia/Shigella, and Streptococcus, rather than bacteria that are known to degrade cellulose from plant matter, such as Ruminococcaceae, and Bacteroides.  Finally, of particular interest in light of the recent research on the importance of diurnal changes in the microbiome, the scientists noted that the panda microbiome undergoes huge shifts in accordance with the seasons, although they do not speculate as to the effects these shifts may be having.

These discoveries are quite surprising, but they help explain why pandas must eat around 25 lbs. of bamboo every day.  Their microbiomes are just not well equipped to digest this food.  In fact, the lack of cellulose degrading bacteria in pandas’ guts has led some scientists to speculate that pandas are merely living off the cellular contents of each plant cell, rather than the energy dense cellulytic plant cell wall.  Whichever the case, their inefficient digestion certainly is not helping them thrive as a species.

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The views expressed in the blog are solely those of the author of the blog and not necessarily the American Microbiome Institute or any of our scientists, sponsors, donors, or affiliates.

The nasal microbiome of infants may impact risk of developing asthma

Many lower respiratory illnesses have been shown to associate with specific lung, throat and nasal bacteria, but the role of the microbiome is still unclear, and mechanisms for the connection have yet to be proven.  Of particular interest is asthma, which affects around 7% of people in the US, and increases a person’s risk for many other conditions.  While it is normally diagnosed in toddlers, scientists believe that the groundwork for the disease is actually laid during infancy.  With that in mind, researchers in Australia performed the first longitudinal study of infants’ nasopharyngeal (nose and throat) during the first year of their lives, and tracked episodes of respiratory illness during that time.  They discovered a strong connection between the microbiome and respiratory illness, including asthma, and last month published their results in Cell Host and Microbe.

The researchers collected nasopharyngeal microbiome samples from 234 infants at different time points during their first year of life.  Most infants’ microbiomes were dominated by the following species: Moraxella catarrhalis, Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenzae, and Alloiococcus otitidis.  Interestingly, this was true for infants regardless of birth delivery mode (i.e. cesarean or vaginal) as well as length of breast feeding.  In contrast, having a furry animal in the house tended to increase the abundance of Streptococcus, but having older siblings tended to decrease it.  In addition, there were strong seasonal effects on the microbiome, with Haemophilus being associated with the summer, and Moraxella the winter.  In children with respiratory illness, Haemophilus, Moraxella, and Streptococcus were most frequently measured, and Staphylococcus, Alloiococcus, and Corynebacterium least frequently measured.

When the scientists compared their results with the asthma outcomes of the children at 5 years old they noticed one significant trend.  Colonization by Streptococcus at around 2 months old, which was asymptomatic at the time and occurred in 14% of infants tested, was strongly connected to chronic wheezing (itself an indication of asthma) at 5 years old.  They suggest that the developing airways in infants may be especially vulnerable to Streptococcus.

This long term study does a really nice job of defining how the microbiome grows and develops in the airways of infants – something which previously hadn’t been performed at such a large scale.  While this study alone does not figure out exactly what the microbiome’s role is in childhood respiratory illnesses, it does provide a baseline for future studies to work off of.   

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The views expressed in the blog are solely those of the author of the blog and not necessarily the American Microbiome Institute or any of our scientists, sponsors, donors, or affiliates.

How does a man’s seminal microbiome alter a woman’s vaginal microbiome?

There is very little research on the microbiome of semen.  We know that it is not sterile, and some scientists think that some of the bacteria found in semen may be involved in male fertility issues.  However, there is still a lot of research to be done in this area.  Even less is known about how the seminal microbiome influences the vaginal microbiome after sex.  Some research has suggested that specific sexual partners can cause bacterial vaginosis (BV), however the mechanisms for this are unclear.  It is suggested that perhaps the penile and seminal microbiome being transferred to the vagina during sex could cause this, although research has not confirmed these hypotheses.  Researchers from Estonia tried to answer these questions, and studied just how the vaginal and seminal microbiomes change before and after sex.  They published the results of their findings last week in Research in Microbiology

The scientists measured the seminal and vaginal microbiomes before and after sex for 23 couples who had sought help for infertility but were otherwise healthy.  They learned that the seminal microbiome, while containing much fewer bacteria, was actually more diverse than the vaginal microbiome.  Still though, each shared many of the same bacteria.  These included Lactobacillus, Veillonella, Streptococcus, Porphyromonas and Atopobium.  Interestingly, Gardnerella vaginalis, a bacterium highly implicated with BV, was found more frequently in women who had sex with men whose semen contained leukocytes, itself a phenotype associated with infertility.  While most of the women’s microbiomes did not shift after sexual intercourse, four of them did.  In these women a decrease in Lactobacillus occurred, and a decrease in Lactobacillus has also been highly implicated in BV.

While this study was preliminary, it marks some of the first research on the dynamics of the seminal and vaginal microbiome during sex.  The scientists suggest that the microbiome may be very important to fertility issues, and at the AMI we would not be surprised to learn that it is involved in at least some causes of infertility.  In the near future we will be devoting an entire podcast to the vaginal microbiome, and interviewing Jacques Ravel, a world leader in this field.  If you have any relavent questions and would like us to ask them on the podcast please call 518-945-8583 and leave your question on the voicemail.

Please email blog@MicrobiomeInstitute.org for any comments, news, or ideas for new blog posts.

The views expressed in the blog are solely those of the author of the blog and not necessarily the American Microbiome Institute or any of our scientists, sponsors, donors, or affiliates.

Breastmilk varies between mothers – affects microbiome of infant

Chemical structure of fucose molecule

Chemical structure of fucose molecule

We know that breastmilk is crucial to the development of a healthy infant’s microbiome.  It contains many oligosaccharides that cannot be digested by the infant, and whose primary purpose appears to be stimulating the growth of specific microbiome bugs.  There are, however, differences between new mothers’ milk.  For instance, some mothers cannot produce 2′-fucosylated oligosaccharides, which are oligosaccharides that have a fucose sugar on the end.  David Mills and his team at UC Davis recently investigated how the microbiomes of infants differed based on the presence or absence of fucosylated glycans in the milk that they drank.  They published their work in the journal Microbiome last week.

Forty four infants who were fed breast milk had their microbiomes measured throughout the first 120 days of their lives.  Thirty two of these infants were fed milk from woman with fucosylation ability (secretors), and twelve were from women without the fucosylation ability (non-secretors).  When the researchers investigated the contents of the milk they found that it varied in many ways, besides fucosylation.  For example, those women that did not fucosylate appeared instead to increase their monosaccharide sialylation, a sugar that has been linked to C. difficile infection.  When the scientists compared the infants’ microbiomes in the two groups they discovered that secretor-fed infants achieved higher levels of Bifidobacteria and Bacteroides, and achieved these levels more quickly than non-secretor-fed infants.  Instead, the non-secretor-fed infants had relatively higher levels of Enterobacteria, Clostridia, and Streptococci.

These differences may be important to the infants’ developments.  For example, Bifidobacteria in the gut is associated with lower gut permeability and less inflammation.  Also, Bifidobacteria and Bacteroides are large contributors to the production of short chain fatty acids and lactate, which have each been associated with gut health time and time again.  A full 20% of the U.S. population is non-secretors, and it would be interesting to see if any epidemiologically significant differences exist between the two groups into adulthood.  In either case, in the future it may be worth considering supplementing infant milk with fucosylated oligosaccharides if the lack of fucosylation does turn out to be detrimental to the baby.

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The views expressed in the blog are solely those of the author of the blog and not necessarily the American Microbiome Institute or any of our scientists, sponsors, donors, or affiliates.

The lung microbiome changes during cystic fibrosis flare-ups

Cystic fibrosis is a genetically inherited disease characterized in part by thick mucus secretion that can obstruct the lungs and aid in the harboring of bacteria in airways. A leading cause of death within persons with cystic fibrosis (CF) is infection of the lungs and inflammation that leads to respiratory failure. In a study performed by members of the Department of Pediatrics and Communicable Diseases at the University of Michigan Medical School, and published by Microbiome, sputum (mucus) samples were taken from four CF patients over a period of a days leading up to pulmonary exacerbation, a period of worsening lung infection. The hope was to identify possible bacterial changes that lead to exacerbation.

 The samples collected from individuals with cystic fibrosis – referred to as subjects A, B, C, and D – were sequenced to identify bacterial and viral content during the period leading up to and including exacerbation. At baseline, the most abundant bacteria in subject A was Staphlyococcus, in subject C Streptococcus, and in subjects B and D Burkholeria. Subject A showed to most change in bacterial communities during the week prior to exacerbation symptoms, subject B showed bacterial community change just after onset of exacerbation, and subjects C and D remained relatively stable with the onset of exacerbation. After the changes that occurred in subject A’s bacterial community it never bounced back to its pre-exacerbation population, and stabilized to one with reduced Staphylococcus and increased Pseudomonas and Prevotella. Different from subject A, subject B’s bacterial community shifted one week after the onset of exacerbation from one dominated by Burkholderia  to Pseudomonas.

 While there were many differences among the four subjects sampled in the study, there was one similarity in that the dominant taxa of subjects A, B, and C all decreased in relative abundance around the period of exacerbation. The study’s findings also suggest that rather than changes in total bacterial density, it is more likely that shifts in relative abundance of a member of a bacterial community is associated with changes in CF symptoms. Additionally, none of the respiratory viruses tested for were found present during time of exacerbation, which was surprising to the researchers.

 The results of this study do not give us any solid rules for the characteristics of bacterial communities in the lungs during time of exacerbation in cystic fibrosis patients; however it is a step in the right direction toward identifying such characteristics. Perhaps with a larger sample size we can better understand the changes in community composition that lead to changes in CF symptoms.  

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The views expressed in the blog are solely those of the author of the blog and not necessarily the American Microbiome Institute or any of our scientists, sponsors, donors, or affiliates.