Bacterial "Vampirism" Fuels Deadly Infections

Scientists have discovered that some of the world's deadliest bacteria exhibit a behavior akin to "bacterial vampirism," actively seeking human blood as a food source. Remarkably, these bacteria show a particular affinity for serine, an amino acid commonly found in protein drinks and abundant in human blood.

The study’s findings, which were released in the journal eLife, offer fresh perspectives on the causes of bloodstream infections and possible therapeutic approaches.

Bacteria infecting the bloodstream can be lethal. We learned some of the bacteria that most commonly cause bloodstream infections actually sense a chemical in human blood and swim toward it.”

Arden Baylink, Professor and Study Corresponding Author, College of Veterinary Medicine, Washington State University

Human serum has been found to attract three different types of bacteria: Salmonella enterica, Escherichia coli, and Citrobacter koseri. These findings were made by Baylink and the study's lead author, Siena Glenn, a Ph.D. Candidate at WSU.

For approximately 1% of the population who suffer from inflammatory bowel diseases (IBD), these bacteria are a major cause of death. These patients frequently experience intestinal bleeding, which may provide a gateway for the bacteria to enter the bloodstream.

The researchers replicated intestinal bleeding using a powerful microscope system created by Baylink, known as the Chemosensory Injection Rig Assay, by injecting tiny amounts of human serum and observing as the bacteria traveled toward the source. The disease-causing bacteria respond quickly; in less than a minute, they locate the serum.

As part of the investigation, the scientists discovered that Salmonella has a unique protein receptor known as Tsr, which allows the bacteria to detect serum and swim toward it.

They were able to see the protein’s atoms interacting with serine through a method known as protein crystallography. According to scientists, one of the substances in the blood that the bacteria detect and eat is serine.

By learning how these bacteria are able to detect sources of blood, in the future we could develop new drugs that block this ability. These medicines could improve the lives and health of people with IBD who are at high risk for bloodstream infections.”

Siena Glenn, Study Lead Author and Ph.D. Candidate, Washington State University