Researchers take aim at rapid detection of sepsis in neonates
“This research started when I was working as a postdoc at Notre Dame, where we were trying to develop a faster way of detecting viable bacteria for an environmental application,” Sengupta said. “Our original idea was that using electrical impedance measurements, we would be able to detect gas production by living bacteria. But a closer analysis of the data revealed that we were on to something more sensitive — charge storage at individual viable cells.”
Sepsis is the 10th leading cause of death in the United States. It is estimated that 28 percent of sepsis cases in the United States are fatal and that the annual cost of treating septic patients is in excess of $16 billion. Seven percent of neonate deaths are traced to sepsis.
Sengupta received a $180,000 research award from the Wallace H. Coulter Foundation to validate and advance the potentially life-saving technique, as early detection of viable bacteria in the blood is the key to effective treatment of sepsis. The foundation funds translational research in biomedical engineering with the goal of accelerating the introduction of new technologies into patient care.
In cooperation with collaborator John Pardalos, MU Health Care’s medical director of the neonatal intensive care unit at the Women’s and Children’s Hospital and MU associate professor of clinical child health, Sengupta’s team has been working to prove that his electrical impedance method is consistently accurate, faster and less expensive than current technologies.
Sengupta explained that generally 10 cubic centimeters of blood are drawn from patients in the hospital to perform a “blood culture” test if infection is suspected, though only one cc. is extracted from infants. The blood sample is added to a bacterial growth medium that supports the growth of almost all microorganisms. Hospital technicians then monitor it for up to five days for signs of carbon dioxide (CO2) production, which indicates the presence of living and thriving bacteria in the drawn blood.
“Using current technology, it typically takes 12 to 72 hours — up to three days — to get a positive reading. They run it for five days before declaring it negative,” Sengupta said.
“Instead of looking for CO2 production, we do an electrical scan on a small blood sample,” the researcher explained. “If you hit bacteria with a high frequency AC field, they experience membrane polarization and the cells store a charge. We can pick up signatures of this charge storage with an impedance analyzer in a much shorter time.”
For testing purposes, bacteria are added to blood culture broths and gently rocked in an incubator at 37 degrees Celsius.
“Every hour, we take a small amount and put it on a plate to see how many bacteria there are, and put some in microfluidic cassettes to take electrical readings,” said Sachidevi Puttaswamy, a doctoral student working with Sengupta. Because of its incidence of fatality, it is common practice for doctors to put the patient on a broad-spectrum antibiotic at the slightest suspicion of sepsis, though such a drug may not be as effective as one that specifically targets a known bacterium and might also be costly. When a sample comes back positive, the bacteria must then be identified with a panel of selective media, or using DNA-based methods. According to Sengupta, while the identification is relatively fast, the preceding culture step is the key cause of delay in administering the targeted antibiotic. He said that in infants, sepsis can be fatal in three days, and the more rapidly the most appropriate antibiotic is identified and administered, the lower the incidence of mortality.
“It will speed up the recovery process if the baby can be put on the correct antibiotic more quickly — something that is more specific and isn’t so broad,” said Pardalos. “And a more specific antibiotic will also decrease the possibility of antibiotic resistance.”
“With this technique, we can cut down the bacterial detection time to five hours, and we will also be able to say after 24 hours that the patient definitely does not have sepsis,” Sengupta said of the research he and Puttaswami are conducting.
“This saves time in the hospital, reducing health care costs,” said Pardalos. “And for me, as a neonatologist, treating a child appropriately is of the utmost importance.”
Sengupta and Puttaswamy have a joint patent on the technology and they are working with a private company, Techshot, to develop and test a single unit automated system to do the testing. This project has been funded by the National Institutes of Health (NIH) through a Phase I Small Business Innovative Research (SBIR) grant, which seeks to increase private sector commercialization of innovations derived from federal research and development.
“The best part about this research is that we’re not just doing something for the sake of doing it,” said Puttaswamy. “It can actually help people. I didn’t realize how sepsis affects people — that it was such a huge problem. This is really important.”
“Being co-owner of a patent is exciting, too,” she added.
“Dr. Pardalos has been wonderful,” said Sengupta. “Having a medical school on this campus is very useful. My decision to come to MU was a good one.”