Bacteremia, or blood poisoning, occurs when bacteria overcome the body’s immune defenses.
Bacteremia can worsen into sepsis, a condition that accounts for more than 1 in 3 hospital deaths per year.
Yet people are routinely exposed to and fight off bacteria from the environment without this deadly series of events occurring.
Scientists are trying to figure out exactly how bacteria spread throughout the body to cause systemic infection in the hopes of eventually stopping this process in its tracks.
Michael Bachman, M.D., Ph.D., clinical associate professor of pathology and microbiology and immunology at U-M Medical School and former postdoc Caitlyn Holmes, Ph.D., have tried to solve this mystery, focusing on gram negative bacteria like Klebsiella pneumoniae, a common source of pneumonia-initiated bacteremia.
In previous work, they determined that bacteria spread in three phases: infection of an initial site, such as the lungs; entrance into the bloodstream; and finally, replication and avoidance of filtration by the liver and spleen.
Traditionally, analyzing a bacterial infection is done by culturing tissue and counting the number of resulting bacteria.
Experimentally, we can measure the first phase pretty easily in terms of how the bacteria infect the lungs and we can measure the third phase pretty easily in terms of how the bacteria survive in these blood-filtering organs and whether they replicate or not. But that transition out of the lungs and into the bloodstream has traditionally been difficult to measure.”
Michael Bachman, M.D., Ph.D., clinical associate professor of pathology and microbiology and immunology,