Tantalizing but preliminary evidence of a “brain microbiome” | Hacker News Reader

Tantalizing but preliminary evidence of a “brain microbiome”

sciencemag.org

192 pointspseudolus67 comments

This is all very preliminary, a couple of quotes from the article stood out to me:

> Roberts wondered whether bacteria from the gut could have leaked from blood vessels into the brain in the hours between a person’s death and the brain’s removal.

> Roberts acknowledges that her team still needs to rule out contamination. For example, could microbes from the air or from surgical instruments make it into the tissue during brain extraction?

But you left off supporting evidence from mouse models: "So she looked at healthy mouse brains, which were preserved immediately after the mice were killed. More bacteria. Then she looked at the brains of germ-free mice, which are carefully raised to be devoid of microbial life. They were uniformly clean."

I had no idea we could sustain germ-free life. That's so cool. The obvious evidence that seems to be missing, however, would just be to extract brain tissue from a living animal, no?

that very much contradicts my model of organisms as well.

I thought we ARE 95% germs, DNA wise.

Prokaryotes are thousands of times smaller in mass/volume, so most cells (and maybe even most DNA) can be bacteria while these are nonetheless minor players.

A side note to passing readers: thousands of times smaller in mass or volume means of course only tens of times smaller in diameter, which agrees with the pictures shown in the article and elsewhere.

Yea. The comparison of humans to cockroaches is a useful intuition. Or blue whales to cats.

This is definitely part of it, the estimates claiming 90% bacteria by cell count end up suggesting perhaps a half gallon of actual bacterial volume. As far as DNA, I think the parent stat can't hold for base pairs. Not as a volume issue, but because mammalian genomes are ~3 orders of magnitude larger than bacterial ones. Even at a 10:1 cell count, our base pairs would be 99% human.

Most importantly, though, the 10:1 stat is just outdated. Newer estimates put the number around 1.3:1 instead.

https://journals.plos.org/plosbiology/article?id=10.1371/jou...

This comment was super interesting, thank you.

That does nothing to rule out contamination from a different tissue.

Different methods. Same result. But sure, you can't prove a negative.

How could one possibly rule out contamination by this logic?

By using some procedure that controls for contamination from a different tissue, instead of having no relation to it.

The truth is that it will probably be hard to find conclusive evidence unless we look for this in a living brain.

Would be fascinating if it turns out to be half as important as gut bacteria. Maybe certain human breakthroughs like the rise of civilization could one day be attributed to a bacterial infection. And then the inverse, changing diets and the brain biome might lead to their collapse.

I've thought the same of viruses as well. If the Zika virus can cause brain damage, perhaps there was another virus (and/or microbe) at some point that made us smarter.

Maybe its bacteria from periodontal disease

"DNA from the periodontal bacteria was also found in the brain tissue of mice in the study group, and a bacterial protein was observed inside their neurons."

https://medicalxpress.com/news/2018-10-periodontal-disease-b...

I know it is just pain radiating from the nerves of the tooth, but a couple times when I had a tooth go abscessed the pain was so intense and in my head I kept thinking my upper mouth is so close to my brain surely this infection can make it from my tooth into my brain. I know about the blood brain barrier but I kept thinking surely it is just a defense and not perfect and a bad infection could push its way in.

Infections in the facial area can indeed be quite serious:

https://skeptics.stackexchange.com/questions/10674/can-poppi...

On that note, a warning:

Do NOT pluck your eyelashes or nose hairs, ever!! These hair roots can cause the trigeminal nerve to become infected which can then lead to meningitis/brain infection and ultimately retardism/coma/death.

Trim if you must -- and do not use a powered trimmer either! The so called "no-pull" nose hair trimmers still cut too short or pull hairs anyways, leading to infection.

Solution: just use mini cat nail scissors. They are actually perfect shape and size to cleave nose hairs at a good length without risk of infection.

If you appreciate quality Japanese craftsmanship that will last a lifetime, I recommend Cattyman. My cats and my nose swear by them. And it's the only brand we carry at the shelter that I volunteer at. [1]

[1] https://amzn.to/2FkyiMv

Source: I am a med student and graduated with honors in Biomedical Sciences

Are eyebrows okay to pluck? I don't ever see myself plucking my eye lashes, but the brows are more common.

Eyebrows are fine to wax, pluck, trim, do anything etc..

It's just eyelashes and nostril/nose hair that are prone to infection.

Source: I am a med student and graduated with honors in Biomedical Sciences

> These hair roots can cause the trigeminal nerve to become infected which can then lead to meningitis/brain infection and ultimately retardism/coma/death.

Huh, that's alarming. Do you have any citations handy about the total relevant risk? Thanks.

This article explains the risks well and provides references at the bottom.

https://en.wikipedia.org/wiki/Danger_triangle_of_the_face

Hm... I've seen this claim and the related claim that popping pimples in that area can cause fatal infections several times.

My first note is that I've never seen someone claim trigeminal nerve infection is the mechanism, and indeed trigeminal nerve infections appear to be exceedingly rare and not directly life-threatening. The relevant disorder would be trigeminal neuralgia, which causes severe and lasting pain, but is almost always a product of compression, inflammation, or demyelination of the nerve. I can't find any record of infection as a cause, only some hypothesizing that atypical forms of the disease might be based on infection. The only major connection I can find between hairplucking and that nerve is the claim that it's responsible for the sneezing reflex many people have when nose hairs are pulled.

As for "can plucking nose hairs kill you?" That's a bit more credible.

The mechanism here isn't nerve infection, it's infection of the veins in the area, which have unusually direct connections to the cavernous sinus and brain. This can lead to meningitis, brain abscesses, and disabling/fatal bloodclots, so I suspect it's the same thing described above. (It's worth noting that normal "sinus infections" can also have the same effect, but the direct bloodflow connection here threatens much faster escalation than normal sinusitis.)

On to rates, then. Meningitis, brain abscess, and cavernous sinus thrombosis (a blood clot in the cavernous sinus) are all exceedingly dangerous, so let's just worry about the rate of getting there.

The base rate of cavernous venous thrombosis is ~1 per 100,000 per year, mostly occurring alongside other major facial infections. Without strong reason to expect that you have heightened risk, it's largely irrelevant.

A 1937 study found that 61% of cases of cavernous sinus thrombosis (which is extremely dangerous) were a product of upper-face boils. Modern rates appear to be closer to 50% of cases, probably down to a mixture of dental surgery causing new cases and antibiotics preventing nasal-infection cases. (A venous infection progressing straight to brain abscess or meningitis appears to be possible, but unlikely without an intermediate infected-sinus stage.) Boils around the middle of the face are viewed as deserving prompt intervention to avoid this outcome.

Unfortunately, there's no clear data on how many of those cases were the result of hair-plucking. Staph infection can lead to boils at any irritated skin site, and are indeed the infectious agent in 70% of thrombosis cases. But severe boils are vastly more common in patients with specific risk factors (family history, immunosuppression, certain disease). Indeed most people who pluck hair never seem to develop boils. (N.b. boils are not the same as 'clean' inflammations from trapped hairs.) At-risk patients are also in far more danger from boils, since they face risks like immunosuppression and frequent treatment leading to drug resistance. One-time cases in healthy patients can be treated simply and effectively with antibiotics, steroids, and lancing.

So: plucking can lead to boils, and boils can lead to thrombosis, and thrombosis can lead to death. But any major infection from plucking appears to come after a noticeable period of surface infection at the site (i.e. a boil). Simple one-off boils are extremely treatable in the presence of modern antibiotics, so the risk can be arrested almost completely at that point as long as you seek prompt medical treatment. (Go to the doctor if you have a boil anywhere anyway, because they rarely heal without treatment.)

As far as I can tell, this is one of those risks which is discussed because it's interesting and logical more than because it actually hurts anyone. "Don't pluck nose hairs" does not seem to be an important precaution unless you have other major risk factors like HIV or a drug-resistant staph infection.

https://en.wikipedia.org/wiki/Danger_triangle_of_the_face

https://www.ncbi.nlm.nih.gov/books/NBK448177/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1390530/

Well, this is pretty great analysis, thank you. My only suggestion is to put your last paragraph, the summary, right at the top so people are more likely to stop being afraid of this stuff. (:

Cheers, that's a good point. Too late to edit, but I tossed the summary in a followup comment.

Not sure how far I can go with Wikipedia, since I think even "I multiplied numbers from three sources together" is original research. Adding the annual frequency of the disease ought to be fair game though, and that's probably the most important part.

Also: I think it would be useful if you were to take this analysis and add it to the relevant wikpedia page that you cited: https://en.wikipedia.org/wiki/Danger_triangle_of_the_face It does say "While the disorder has become extremely uncommon with the development of antibiotics, it still carries a very small chance to develop a high risk of death..." but I don't think that does justice to the minuscule risk involved.

Following a suggestion, the tl;dr:

This gets discussed because it's interesting, not because it actually hurts anyone. "Don't pluck nose hairs" does not seem to be an important precaution unless you have major risk factors like uncontrolled AIDS or a drug-resistant staph infection. Otherwise, go to your doctor promptly if something seems infected and you'll be fine.

Thank you for the info.

On a related subject, do you know anything about the benefits and/or dangers of nose/sinus irrigation?

A few years ago I solved my life-long struggle with chronic sinusitis, rhinitis, and other assorted nasal issues, by washing my sinuses during my daily shower, with warm saline solution.

To anybody who might have bad memories of going to the swimming pool, no, it doesn't hurt at all, if the solution is warm and slightly hypertonic.

I use a plastic Neti pot that I fill with hot water from the shower, to which I add common sea salt with the provided measuring spoon. I rinse from one nostril to the other and vice versa. Then, with my nose full of water and my nostrils closed, I bend 180º upside down and apply very gentle negative/positive pressure to the water with my breath, to wash the upper sinuses. Then blow it all out and repeat a couple times.

The upside-down procedure was key to curing my long-term sinusitis years ago. I had been doing the procedure for a few days, when I saw a tiny glob of stuff wash away from my nose's upper sinuses and felt the unholy stench of anaerobic bacteria. From that day on, I stopped having weekly common colds and other issues (that the doctors couldn't cure even with antibiotics.) So it was definitely a good procedure and I kept doing it every day.

But recently I've read about possible dangers with nose irrigation, how one is supposed to boil the water before using it and change the Neti pot regularly.

Is there any truth to these fears? Should I go to the—admittedly—troublesome step of boiling and cooling the water I intend to use, instead of taking it from the shower?

And if so, are there any tests I would be advised to perform, to make sure I didn't contract anything by my simple washing method?

There is a decent guide by the FDA here:

https://www.fda.gov/ForConsumers/ConsumerUpdates/ucm316375.h...

You might have heard about certain amoebas being a risk of dipping ones head underwater in warmer bodies of fresh water:

https://en.wikipedia.org/wiki/Naegleria_fowleri

You probably won't find Naegleria fowleri in your common tap but there are a host of other protozoans and bacteria that can be dangerous to your health.

Contrary to common belief, they probably won't kill you right away - and may not even cause an infection. But you are taking a risk and taxing your body's immune system and that particular area's sensitivity and inflammatory response. It's really not worth the risk considering the price of generic, sanitized, saline bottles that are less than a few dollars a gallon.

The risk is small but it could end you due to the area we are discussing:

https://en.wikipedia.org/wiki/Danger_triangle_of_the_face

I used aerosol saline sprays after I had deviated septum correction surgery. They are pressurized so there's no risk of internal contents becoming contaminated. This alone is worth the peace of mind. Plus the pressure helps in a way a normal neti pot or drip system cannot.

I used large Neilmed bottles from Walmart but I did a quick search for you and found a 3-pack of Arm n Hammer saline aerosol for $12 which seems to be a solid price: https://amzn.to/2RMiseS

Hope this helps. Good luck with your health, take care of yourself!

I replaced my irrigation device with a new one and now I'm only using water that has been boiled for 5 minutes in a brand new kettle and cooled down.

I'm also considering using specific salt packets instead of common salt.

Thanks again for the info.

I use boiled water for nasal irrigation.

I think we have all kinds of latent bacteria and viruses in our body (including the brain). It's however a interesting though that there might be good brain bacteria, which might affect feelings, emotions, and alertness.

I already see my local dairy industry make money out of this: "Drink our new Brainimel, with the best microbiome for your brain, so you can stay asleep, obey and consume..."

I once had the horror of walking through some drug store and seeing bottled DNA, with a description like "an essential component of life!" At best, I suppose it was an overpriced and inefficient amino acid supplement. At worst, it was effectively a sugar pill.

I'm sure that these studies get any traction, we'll see bacterial 'supplements' almost immediately. Never mind that even gut microbiome supplements are usually destroyed in the stomach, we can definitely make yogurt that gets to your brain!

Where do you live that you have such an aggressive dairy industry?

You haven't heard of Hyperbole Town, have you? :)

I'm a very literal person.

Seems to me that the more we sharpen our mental and methodological tools (in all areas of human inquiry), the weirder and more interesting things become.

Shit's messy, yo!

Can't wait to order some "cerebral-probiotics 2000"

We'll all laugh now but come the incessant infomercials (I'm guessing 2-3 years) and interstitials it won't be so funny.

It would be interesting to find out that a lot of modern psychological diseases might be caused by excessive antibiotic use disrupting the brain microbiome.

Antibiotics can certainly cause problems in the gut microbiome, but let's not jump to conclusions about the brain just yet.

Can antibiotics pass the blood brain barrier?

Some do, including penicillin:

“Antibiotics that cross the BBB tend to have certain physical characteristics including: small molecular size, being lipophilic, binding to fatty molecules on cell membranes, low plasma protein binding and other specialized characteristics“

http://lymemd.blogspot.com/2013/03/blood-brain-barrier.html?...

There is evidence to suggest antibiotics increase risk of anxiety and depression.

https://www.ncbi.nlm.nih.gov/pubmed/26580313

A lot of people who started eating exclusively meat reported their depression, anxiety and (mental) fatigue going away, so this is should not be surprising.

http://meatheals.com/

https://www.youtube.com/watch?v=jrF4aJvdU-A

I can't believe you people haven't brought up the obvious zombie-gut microbiome connection yet...

How is it possible we didn't notice anything like this before?

reminds me of https://en.wikipedia.org/wiki/Archaea

Although these archaea can be present in extremely high numbers (up to 40% of the microbial biomass), almost none of these species have been isolated and studied in pure culture.

Most likely because someone failed to look for it before or those that saw it assumed it was contamination.

Wait a second, how did bacteria get through the blood-brain barrier?

Bacteria associated with meningitis get through with predictable results so what else might?

I do not know a lot about bacterial meningitis, but I don't believe that it actually passes through the barrier. Meningitis is caused by the inflammation of a membrane that the brain and spinal chord are encased within [1]. So it might be causing the membrane to become enflamed from the outward facing surface.

[1] https://www.healthline.com/health/bacterial-meningitis-cause...

There has been some potentially revolutionary work at CalTech with respect to the link between intestinal bacterial and Parkinson's (see link below). If it pans out it could potentially open up entirely new avenues of treatment.

http://www.caltech.edu/news/parkinsons-disease-linked-microb...

By being the same size or smaller than the passages in the barrier.

The blood brain barrier usually only allows particles on the order of nanometers in size, while bacteria are much, much larger.

maybe the barrier is not that leak-proof as current medical postulates? Maybe it's not a barrier after all, just a border?

Everything has limits and fails. So yeah, probably this.

How is babby formed!??

Seriously, is it possible the brain is infected (innoculated maybe?) in utero before the blood brain barrier is formed, or before the skull is formed.

That would be cool: if mothers passed on a colony of bacterias that evolved down the generations.

In that case the barrier is likely semipermeable. It may be that certain bacteria were advantageous to human evolution, so the barrier evolved with a mechanism that allowed good bacteria to pass through. Now this should make us humans a bit concerned about the likelihood of mimics. If good bacteria indeed play a role in human emotion and alertness, then perhaps some mimics result in certain types of mental illness.

Pesticides and plasticizers are known to disturb the blood-brain barrier and allow poisonous substances (and apparently bacteria?) to infiltrate brains.

Marketers lickicking their chops for Yogurt for brain campaigns

Incredible.

What a great idea.

FWIW, that wasn't sarcasm.

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