
Tantalizing but preliminary evidence of a “brain microbiome” - pseudolus
https://www.sciencemag.org/news/2018/11/do-gut-bacteria-make-second-home-our-brains
======
tlow
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?

~~~
SubiculumCode
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."

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

~~~
go_blue_13
How could one possibly rule out contamination by this logic?

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

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flukus
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.

~~~
chiefalchemist
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.

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clumsysmurf
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...](https://medicalxpress.com/news/2018-10-periodontal-disease-
bacteria-kick-start-alzheimer.html)

~~~
14
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.

~~~
adrianN
Infections in the facial area can indeed be quite serious:

[https://skeptics.stackexchange.com/questions/10674/can-
poppi...](https://skeptics.stackexchange.com/questions/10674/can-popping-a-
pimple-in-the-facial-danger-area-cause-brain-infection-or-death)

~~~
goldenkey
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](https://amzn.to/2FkyiMv)

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

~~~
Diederich
> 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.

~~~
Bartweiss
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://en.wikipedia.org/wiki/Danger_triangle_of_the_face)

[https://www.ncbi.nlm.nih.gov/books/NBK448177/](https://www.ncbi.nlm.nih.gov/books/NBK448177/)

[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1390530/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1390530/)

~~~
Diederich
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. (:

~~~
Bartweiss
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.

------
z3t4
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.

~~~
mar77i
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..."

~~~
Something1234
Where do you live that you have such an aggressive dairy industry?

~~~
mar77i
You haven't heard of Hyperbole Town, have you? :)

~~~
Something1234
I'm a very literal person.

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ehecatl
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!

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rawoke083600
Can't wait to order some "cerebral-probiotics 2000"

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

------
empath75
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.

~~~
tgb
Can antibiotics pass the blood brain barrier?

~~~
blevin
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?...](http://lymemd.blogspot.com/2013/03/blood-brain-
barrier.html?m=1)

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sridca
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/](http://meatheals.com/)

[https://www.youtube.com/watch?v=jrF4aJvdU-A](https://www.youtube.com/watch?v=jrF4aJvdU-A)

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

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

~~~
singularity2001
reminds me of
[https://en.wikipedia.org/wiki/Archaea](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.

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

~~~
vixen99
Bacteria associated with meningitis get through with predictable results so
what else might?

~~~
dustfinger
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...](https://www.healthline.com/health/bacterial-meningitis-causes-and-
how-they-re-spread#pictures)

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m3kw9
Marketers lickicking their chops for Yogurt for brain campaigns

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Zaex
Incredible.

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AlexCoventry
What a great idea.

~~~
AlexCoventry
FWIW, that wasn't sarcasm.

