How Clean Should Your Blood Be?

Traditionally, blood is known to be in a sterile environment. If you get any microbes in your blood you’ll have a potentially deadly septic shock, right? well, there have been studies that suggest the existence of a microbiome in a healthy person’s blood. Do vampires need to take antibiotics after each meal?

Why is this important?

Imagine this: you are an ER doctor and there has been a car accident, your patient needs a blood transfusion STAT. You check their blood type and infuse the right type of blood. Your patient stabilizes for now but after a short while, they enter septic shock. You made sure they get the right blood so what went wrong? This phenomenon is called “transfusion-related sepsis” which is caused when a patient is infused with contaminated blood. Fortunately, this is a very rare event (approximately 1 in 100,000) but why does it happen at all? Aren’t we supposed to check blood donors to make sure they’re not sick? I have three words for you: asymptomatic transient bacteremia. That means you have super sneaky microbes in your blood and we don’t know about them because you don’t have any symptoms.

Knowing the blood microbiome (or if it exists) can give us valuable and potentially life-saving information. Some medical conditions might be explained by this microbiome. Moreover, this might even be useful in forensic sciences, and last but not least knowing what microbes we have in our blood can save so many vampire lives!

Do we actually have microbes in our blood?

According to several studies, such as this one which was published on transfusion, and many others, the existence of some bacteria in circulation is normal and accepted. A study was done on 1285 randomly selected people out of the public, convincing the scientists to “consider the blood microbiome as a potential biomarker of human health.” These studies can be used to conclude that even healthy humans have some microbes in their blood.

If you don’t buy this you’re not alone. Recently a group of scientists challenged this view and the methods these studies used. The study which was published in Nature Microbiology, called out the previous studies as “controversial” because “most of these studies were either done in relatively small cohorts or lacked rigorous checks to distinguish true biological measurements from different sources of contamination…”

What does the recent study say?

The scientists first defined a microbiome as “a community of microbes that interact with each other and with the environment in their ecological niche.” That means for a viable microbiome to exist in blood there must be a set of bacteria that interact with each other or at least there should be a strain that is common in all or most individuals. They then used data gathered from 9770 people from different cohorts to conduct various experiments.

For this experiment to be valid, the team had to first filter out all sources of contamination and address any possible false positives. They did this by separating the host genome from the microbial genome and then doing taxonomic checks to make sure the bacteria they found is not a false positive. after all these procedures (and a bunch of other very smart sciency things) they managed to isolate 117 microbial species in the blood of these healthy individuals.

So that means there actually is a microbiome right? well not exactly. the species they found were not common amongst different subjects but these bacteria also existed in other body sites. What this means is it is more probable that these microbes somehow got into the blood from another source and are not “native” if you will, to blood.

Bottom line

Do you have microbes in your blood? maybe, but that doesn’t mean you have a microbiome in your blood. it is important to consider what language you’re using when referring to scientific topics. these microbes that might be in your blood, probably come from some other place in your body (your gut for example which does have a microbiome.) In any case, you should not worry about microbes in your blood if you’re healthy. But if you’re a vampire make sure you have some penicillin on hand.