Scientists discover 'vampire bacteria' drawn to human blood, offering hope for new treatments

Researchers at Washington State University have identified a phenomenon they're calling bacterial vampirism: three common disease-causing bacteria actively hunt for human blood and feed on it, a discovery that could reshape how doctors treat life-threatening bloodstream infections.

The bacteria in question—E. coli, Salmonella enterica, and Citrobacter koseri—don't passively encounter blood. They sense it. They swim toward it. Using a specialized microscope system called the Chemosensory Injection Rig Assay, Professor Arden Baylink and doctoral student Siena Glenn watched as the bacteria navigated toward microscopic amounts of human serum in less than a minute. The bacteria were drawn to a specific amino acid in the blood called serine, which the organisms use as food. It's a predatory behavior happening at a scale invisible to the naked eye, but with consequences that are very real.

The implications are sharpest for people with inflammatory bowel disease. About one percent of the population lives with IBD, and for them, these bacteria represent a leading cause of death. The disease itself causes intestinal bleeding—small wounds in the gut lining that become highways for bacteria to enter the bloodstream. Once there, a bloodstream infection can turn lethal quickly. Understanding how the bacteria find their way in is the first step toward stopping them.

What makes this discovery actionable is the mechanism. The research team, publishing their findings in the journal eLife, determined that Salmonella uses a special protein receptor called Tsr to sense serine and orient itself toward the source. Using protein crystallography—a technique that reveals the atomic structure of molecules—they watched the protein interact with serine at the molecular level. This isn't abstract biology. It's a specific lock-and-key system that could, in theory, be disrupted.

Glenn articulated the path forward clearly: by understanding how these bacteria detect blood, researchers could develop drugs that block that ability. Such medicines wouldn't need to kill the bacteria outright. They would simply blind them to the presence of blood, preventing the infection from taking hold in the first place. For IBD patients already managing a chronic disease, the ability to prevent a secondary, often fatal infection would be transformative.

The work sits at the intersection of basic science and urgent clinical need. Bloodstream infections are among the most dangerous complications in medicine, and the bacteria involved here are common culprits. The fact that they actively seek out blood—that they're not passive invaders but active hunters—changes how researchers think about prevention. It also explains why some people are more vulnerable than others. An IBD patient with intestinal bleeding isn't just at risk from any stray bacteria; they're at risk from bacteria that will actively find the wound and exploit it.

The next phase is drug development. The researchers have handed off a clear target: the serine-sensing machinery. Pharmaceutical teams can now work on compounds that would interfere with that system, potentially creating a new class of preventive treatments. For a population that already bears the burden of chronic disease, the prospect of preventing a complication that kills is more than incremental progress. It's the difference between managing an illness and surviving it.