Deadly bacteria from around the world have been found to seek out and feed on human blood.
Researchers at Washington State University (WSU) discovered a new trait called “bacterial vampirism” among bacteria such as Salmonella and E. coli, which cause foodborne illnesses.
It has long been a mystery how and why these microorganisms can move so deftly from the intestine to the blood, where they can be deadly.
The team discovered that these bacteria are attracted to the liquid part of the blood, or serum, which contains nutrients that the bacteria can use as food.
Pathogens can easily find where the serum is and enter the bloodstream through small cuts in the digestive system, sometimes causing death from sepsis in people with inflammatory bowel disease.
Even the smallest amount of blood is enough to attract vampire bacteria, such as sharks with their famous ability to detect one drop of blood in 10 billion drops of water.
Washington State University researcher Arden Baylink holds a petri dish containing salmonella bacteria. Baylink and PhD student Siena Glenn have published research showing that some of the world’s deadliest bacteria seek out and eat whey, the liquid part of human blood, which contains nutrients that bacteria can use as food.
Bacteria such as E. coli can leak into the bloodstream through lesions in the intestine of people with inflammatory bowel disease, causing serious complications.
Co-author Arden Baylink, a professor at WSU’s College of Veterinary Medicine, said in a statement: “Bacteria that infect the bloodstream can be lethal.”
“We learned that some of the bacteria that most commonly cause bloodstream infections actually detect a chemical in human blood and swim toward it.”
According to the new studypublished in the journal eLife, enterobacteria such as E. coli and Salmonella It can detect as little as one femtoliter of serum, a small amount equivalent to 0.0000000000001 milliliters.
Once they find the cut that is leaking blood into the intestine, they go around it and enter.
It’s much like how sharks can search for prey in their blood, but bacteria don’t have noses, so they rely on other senses.
The team used a high-powered microscope system to simulate intestinal bleeding by injecting microscopic amounts of human serum and watching as the bacteria navigated toward the source.
They watched the microbes search for the serum and found that it took less than a minute.
In this case, it’s a strategy called “chemotaxis,” in which bacteria move toward higher concentrations of specific substances.
The team also determined that Salmonella has a special protein receptor called Tsr that allows the bacteria to detect and swim into the serum.
In the discovery of Tsr, researchers used a form of high-resolution microscopy to observe the atoms of the protein that interact with serine.
Siena Glenn, Ph.D. from Washington State University. student uses high-powered microscope to study deadly bacteria like E. coli and salmonella
Scientists believe that serine is one of the blood chemicals that bacteria detect and consume.
This new understanding of how bacteria can lodge in the bloodstream paves the way for new drugs that will prevent sepsis before it even occurs, rather than treating it once someone is sick, the scientists behind the new study said.
«By knowing how these bacteria are able to detect blood sources, in the future we will be able to develop new drugs that block this ability. These drugs could improve the lives and health of people with inflammatory bowel disease who are at high risk for bloodstream infections, said Ph.D. student Siena Glenn, co-author of the study.
Intestinal infections are usually resolved by the immune system without serious problems, perhaps some diarrhea.
But people who suffer from inflammatory bowel disease, including Crohn’s disease and ulcerative colitis, are at much higher risk of developing bleeding within the intestine, which can allow bacteria to enter the bloodstream and cause a more serious bacterial infection.
This puts them at particularly high risk of developing a condition called sepsis, which is essentially a chain reaction of the immune system attacking the body in response to an infection.
Understanding exactly why gut bacteria are prone to entering the bloodstream through small tears or cuts in the intestine may help scientists prevent serious illness in people with these chronic conditions.
Under normal circumstances, there are populations of bacteria in our gut that are often considered harmful, such as E. coli and salmonella.
Other bacteria and our immune system keep them in check when we are healthy.
But if they enter our bloodstream, they can cause sepsis.