By Deborah Borfitz
April 14, 2022 | Coagulation factor proteins in the blood might be incorporated into standard blood tests to rapidly detect sepsis soon after infection but before disease symptoms such as excessive inflammation and blood clotting have happened, suggests a research initiative that markedly increased the survival of mice. If replicated in humans, the testing approach could allow for early detection and treatment of a syndrome that causes sequential organ damage and currently claims more lives worldwide than cancer or coronary disease.
“The best treatment for sepsis starts with rapid detection,” says Michael Mahan, professor of microbiology at the University of California, Santa Barbara, and one of the project leads. “For every hour of delay in antibiotic treatment, there is a 75% increased risk in death.”
Early detection and treatment are related and notoriously hard nuts to crack, says Mahan, cofounder of the long-shuttered biotech Remedyne Corporation. “More biotech companies have failed trying to solve sepsis than all other human medical conditions combined.” The strategy of pharmaceutical companies has been to purchase the one-in-20 biotech survivors in lieu of doing much antibiotics research at all.
On the academic front, Mahan and his team succeeded in detecting a catastrophic shift in blood protein abundance indicative of sepsis in mice, as recently described in eBioMedicine (DOI: 10.1016/j.ebiom.2022.103965). Importantly, these coagulation factor proteins are “induced but inactive” in early stages of infection, says Mahan.
The early-detection riddle might be solved if the findings can be replicated in humans, he says. That, in turn, could help address the antibiotic resistance crisis.
“We showed in our paper that the later you treat with antibiotics, when you take those antibiotics away you see massive disease relapse and the mice died,” Mahan says. Antibiotics cleared bacteria better when infected mice were treated earlier, with a lower dose and shorter duration than would be thrown at sepsis once organ damage had already occurred—the stage at which most human cases present in hospital emergency rooms.
Sepsis is lethal, killing one in four patients hospitalized with the organ failure syndrome and causing lifelong functional disability and cognitive decline as well as a shortened lifespan for many of the rest, says Mahan. The current state-of-the-art diagnostic test for sepsis at the best medical centers in the world is a sequential organ failure assessment (aka SOFA) score to assess the extent of damage.
Systemwide clotting, called disseminated intravesicular coagulation, is the end game with sepsis, but often the kidneys are one of the first organs to fail because the body’s tiniest and most easily obstructed blood vessels (capillaries) are involved in the removal of wastes and excess fluid and release of hormones regulating blood pressure, he explains. Capillaries are likewise used by the lungs to exchange oxygen and carbon dioxide. When blood can’t get through, cells die, and organs permanently fail.
The heterogeneity of the human population and sepsis syndrome is “the killer,” Mahan says. “They are not all the same [and no one knows why], but what is the same is that if you can detect [the condition] early, you can treat [patients] early.”
Using certain coagulation proteins as biomarkers of sepsis provides a path toward development of a diagnostic test that has alluded scientists for decades, he continues. It would be useful not only to hospital-based intensivists but also physicians’ offices with patients who don’t feel well but are not yet cascading toward death.
The technology and methodology used by the research team is open source and freely available to all, he points out, while work continues at the academic level. “This is about saving lives… [and] fair access to precision medicine.”
Small Biopanel
The research team embarked on the project “strongly believing” that the body knows it is going into sepsis much quicker than physicians do, says Mahan. Evidence of this came by orally infecting mice with Salmonella Typhimurium and observing what happened.
The mice didn’t start to show symptoms until day five and then progressively became sicker until their death between days eight and 10, he reports. To investigate what was going on days two through seven, they drew blood on successive days to find a cataclysmic upsurge in 119 proteins. Being part of a large sepsis consortium funded by the National Institutes of Health with considerable expertise in coagulation—notably, Dzung T. Le at UC San Diego Medical Center who ran the coagulation factor assays as well as study co-authors at UC Santa Barbara and the Sanford Burnham Prebys Medical Discovery Institute—they then homed in on the smaller subset of proteins that help control bleeding.
The jump from mouse to man is a big one, Mahan acknowledges, and for simplicity’s sake will entail development of a biopanel of the three to five “most important” coagulation proteins to integrate into existing blood tests enabling sepsis prediction before excessive clotting and extensive organ damage. In contrast, patients presenting in the emergency room with severe sepsis will typically be tested for 10 to 15 coagulation factor proteins contributing to organ damage.
Further rodent studies will then be done using the smaller panel, he continues. But researchers also have access to human samples, through their affiliation with the sepsis group, which they also plan to utilize as soon as possible.
Trio Of Problems
Researchers are optimistic the findings from rodents in the lab will translate to real-world patients due to the similarity between patterns of how blood proteins are expressed in the two species, says Mahan. And, as one reviewer on the paper indicated, it could help critical care physicians under antibiotic stewardship pressures to justify occasions when higher doses and longer periods of treatment are in fact the only alternative.
“One problem at a time,” Mahan continues. “There is another problem here—antibiotics don’t work as well when people are severely sick and already have blood clotting and organ damage.” Not only are there more bacteria to kill, but the clotting damage done to the body prevent antibiotics from getting to where the bacteria reside.
Yet another problem is the inability to identify the type of bacterium in 30% to 50% of blood samples from hospitalized sepsis patients, says Mahan. Not knowing which antibiotic would best counter the culprit bacteria, and with patients’ health quickly deteriorating, physicians have no choice but to administer a broad-spectrum cocktail of antibiotics because it’s too late to do anything else.
Humans cannot tolerate more than about 10 bacteria per milliliter of blood, which is “really low and hard to detect,” he notes. At that point, the body mounts an overreactive, “friendly-fire” response to the infection that triggers the inflammation and coagulopathy seen with sepsis syndrome.
Patients with sepsis don’t have a blood infection, points out Mahan. They have an organ or tissue infection of uncertain origin, and the bacteria then get released into the blood. In terms of positive outcomes, all the IV fluids and fancy oxygen machines are secondary to quickly initiating antibiotic treatment.
Once patients are crashing, there may be no time to even try identifying the pathogen—a urinary tract infection with Escherichia coli, for instance, might take 18 to 20 hours to culture. “Time to treatment, time to treatment, time to treatment—those are the three most important things for sepsis patients,” he emphasizes.
Stratifying Infections
One promising finding of the recent study that Mahan says he is particularly excited about is that a “specific pattern” of coagulation proteins appears to define the two main classes of bacteria, namely Gram-positive (e.g., S. aureus and Streptococcus pneumoniae) and Gram-negative (e.g., E. coli and Salmonella enterica). The latter are harder to kill because they have two surface membranes that antibiotics must penetrate.
Specifically, the researchers found that these Gram-negative bacteria all had a very similar signature of coagulation proteins that get active in later infection, he says. “This leads to the possibility of being able to stratify Gram-positive and Gram-negative infections early and… put [patients] on antibiotics that work against those bacteria. That would be like giving physicians a cannon; right now, all they have is a squirt gun.”
All sepsis is not the same in the early phase before patients’ organs are failing, says Mahan. But it “coalesces” into one intractable condition at the end point before death.
Most of the 119 proteins abundantly present in the blood with early sepsis infections have nothing to do with coagulation and might likewise serve as potential harbingers of trouble, Mahan notes. “There are a lot of opportunities to explore [and] we have many shots to getting a test that will work.”