Scientists at Washington State University (WSU) have uncovered a startling behavior among some of the world’s deadliest bacteria — they’re attracted to human blood, a phenomenon they’re terming “bacterial vampirism.”

A recent study published in the journal eLife led by researchers from WSU reveals that certain bacteria, including some foodborne bacteria, have a strong affinity for the liquid component of blood, known as serum, which contains vital nutrients for their sustenance. Among the chemicals in blood that these bacteria are particularly drawn to is serine, an amino acid abundant in human blood, also commonly found in protein drinks.

The research, spearheaded by WSU’s College of Veterinary Medicine, looks at how bloodstream infections occur and offers potential avenues for treatment. Arden Baylink, a professor at WSU and corresponding author for the research, emphasized the severity of bloodstream infections, which can prove fatal. “We learned some of the bacteria that most commonly cause bloodstream infections actually sense a chemical in human blood and swim toward it,” said Baylink.

The study identified three types of bacteria — Salmonella enterica, Escherichia coli, and Citrobacter koseri — as being attracted to human serum. These bacteria are known culprits behind bloodstream infections, particularly among individuals with inflammatory bowel diseases (IBD) who often experience intestinal bleeding, providing entry points for bacterial invasion into the bloodstream.

Using an innovative microscope system called the Chemosensory Injection Rig Assay, the researchers simulated intestinal bleeding by introducing tiny amounts of human serum and observed the rapid response of disease-causing bacteria as they homed in on the serum source within minutes.

Further investigation revealed that Salmonella possesses a specific protein receptor called Tsr, enabling it to sense and navigate toward serum. By employing protein crystallography, the researchers scrutinized the molecular interactions between the bacterial protein receptor and serine, pinpointing serine as a key chemical cue from blood that bacteria detect and consume.

Siena Glenn, lead author of the study and a Ph.D. student at WSU, highlighted the potential implications of their findings for developing new therapeutic strategies.

“By learning how these bacteria are able to detect sources of blood, in the future, we could develop new drugs that block this ability,” said Glenn.

Contributors to the research include scientists from the University of Oregon and WSU, with funding provided by WSU and the National Institute of Allergy and Infectious Diseases.

The discovery of what the researchers term “bacterial vampirism” represents a significant advancement in understanding the behaviors and mechanisms underlying bloodstream infections, opening doors for targeted interventions to combat these deadly pathogens.

The full study can be found here.