Back to blog

Swallowing Door Keys and Other Bacteria Acquisition

You’re swallowing things from the minute you’re born.
Especially bacteria.

Towards the end of a night of heavy partying in 2006, a student’s friends wanted to take him home after he’d had a bit too much to drink.

However, not wanting to leave the fun, the student actually swallowed his room key.

SONY DSC

This act of momentary alcohol-fueled madness resulted in a trip to the E.R. the next morning, where the doctors sent him home, telling him to let nature take its course.

31 hours later it did just that, and apparently, after a thorough rinse, the key was placed back on his key chain, saving him the $30 his landlord would have charged for a replacement.

Humans swallow all kinds of odd things, but it’s also the way that bacteria get into our guts, and it’s a good thing too, as a lot of them can actually be very helpful, or at least harmless.

The process of building your microbiome begins at birth. In fact, for babies born vaginally, their very first taste of life comes from their mom’s microbes.

A custom brew of vaginal and fecal flora, including Lactobacillus, Bifidobacterium, E. coli, and Enterococcus covers a mother’s pelvic floor and perineum, perfectly placed for the emerging infant.

Some of the bacteria stays on the skin, and some goes into the mouth, down into the stomach, and then on into the intestine.

Since newborns don’t yet have very acidic stomachs, mom’s bacteria tend to make it all the way down to the gut.

Incidentally, the adult gut is generally highly acidic.

The pH scale runs from 1 to 14, with low numbers indicating acidity and high numbers representing alkalinity. Gastric (stomach) acid can weigh in at a pH between 1 and 3, which is about five times more acidic than lemon juice.

Meanwhile back at the cradle, babies begin to add more bacteria to their microbiome soon after birth.

Staphylococcus aureus gets transferred from the mother’s nipple during breastfeeding, and also from the kisses and cuddles of adoring visitors.

And breast milk itself provides useful microbes such as Bifidobacteria, which after a few weeks can make up more than 90% of a breastfed baby’s intestinal flora.

This model of “bacterial inoculation” has been well-accepted for a long time.

However, two reasonably recent studies have cast new light on the process.

The first, involving research by Spanish scientists in 2006, showed that a baby’s first poop (called meconium) does actually contain bacteria.

Previously it had been believed that babies were born with sterile guts.

Then came a fascinating 2014 study conducted by the Texas Children’s Hospital and Baylor College of Medicine in Houston that discovered bacteria within the tissue of the placenta. Their profile most closely matching the mother’s oral, rather than vaginal, microbiota.

How on earth did these bacteria get there?

The researchers suggested that they may somehow have passed through the bloodstream from mouth to placenta, and were then passed on to the infant, either through the bloodstream or by the baby swallowing amniotic fluid.

As a child develops, so does its microbiome, with new bacteria either hitching a ride on food, or sometimes via dirt and other objects (hopefully not keys) placed in the mouth.

As we saw last week, touching random surfaces can get hazardous.

An 18-month study run by Weill Cornell Medical College got high school and graduate students (yay citizen science!) to swab surfaces on the New York subway system.

48% of the bacteria they collected were unknown to science, and one station that had been flooded during Hurricane Sandy still had microorganisms most closely representing a marine environment.

An earlier claim that this study also found traces of anthrax and plague on the subway was fortunately withdrawn, but the overall take-away is that there are a lot of bacteria out there.

Strange that more of it doesn’t end up in our guts, then—our microbiomes stay pretty stable over time.

Maybe it’s because of the stomach’s extreme acidity, which tends to kill off a lot of stuff?

Or perhaps, like the student’s key, they simply pass on through.


 

Further reading

Babies are born dirty, with a gutful of bacteria

Baby’s first gut bacteria may come from mum’s mouth

Bacteria found in healthy placentas

Geospatial Resolution of Human and Bacterial Diversity with City-Scale Metagenomics

Gut Flora: A Digestible Account of Probiotics

Pneumonia – adults (community acquired)

Pretty Much All of Your Weird Germ-Avoidance Behaviors Are Pointless

Student eats key so he can keep partying

The long road from Data to Wisdom, and from DNA to Pathogen

The Placenta Harbors a Unique Microbiome

There’s No Plague on the NYC Subway. No Platypuses Either.

Where Does The Bacteria In Our Gut Come From?