A blood sample is loaded in a prototype point-of-care testing (POCT) instrument.

Finding Deadly Pathogens—Fast

June / July 2010 By: Kristen Light Volume 8 Number 3

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Consider this scenario: an elderly man is brought to an emergency room confused, disoriented, and shaking severely with chills and fever. His heart is beating rapidly, and his blood pressure is dangerously low. The patient appears to be in a state of shock.

What doctors suspect, but can’t immediately confirm, is that he is suffering from extreme sepsis, a serious medical condition characterized by a whole-body inflammation and the presence of a bloodstream infection. Sepsis is the second-leading cause of death in noncoronary intensive-care-unit patients and the tenth-most-common cause of death overall in the U.S., according to the Centers for Disease Control and Prevention. If the patient does not receive swift medical intervention, death is imminent.

A new blood-borne-pathogen detection technology may in the near future allow doctors to diagnose serious bloodstream infections within an hour. Conventional lab tests typically take several days.
Furthermore, instead of transporting a blood sample to a hospital, trained medical personnel could make a diagnosis at an emergency shelter or at the scene of a disaster. These and other advances are expected to result from a five-year, $8.5 million grant to a team of scientists, engineers, and physicians from Lawrence Livermore National Laboratory and the University of California at Davis that focuses on point-of-care testing, known as POCT.

POCT is defined as diagnostic testing at or near the site of patient care. “According to a recent study from the University of Manitoba in Canada, during the first six hours after the onset of septic shock, the mortality rate increases seven percent for every hour that a patient doesn’t receive effective antimicrobial treatment,” says Livermore chemist Brian Baker, who works in the laboratory’s physical and life sciences directorate. “For treatment to begin without delay, health care workers need to quickly identify which blood-borne pathogen has infected the patient.”

The National Institute of Biomedical Imaging and Bioengineering awarded the grant in 2007. The collaboration was funded as part of the institute’s Point-of-Care Technologies Research Network, which includes three other medical research centers that are part of a larger research effort. The grant provides funds for developing and testing two single-channel prototype instruments, each of which can simultaneously detect five bacterial and fungal blood-borne pathogens. The first-generation POCT device measures about 40 by 50 by 50 centimeters and is designed for hospital settings, while a smaller, second-generation device will be designed for deployment to remote disaster sites.

Five pathogens were selected based on their clinical significance, occurrence in hospitalized patients, threat to the community, and frequency of being found in wounds on victims of severe floods and other weather-related natural disasters. Infections with any one of these five pathogens can lead to sepsis.

The detection process begins with loading a blood sample in the POCT instrument. The device then automatically handles all the remaining processing steps. Instead of relying on the polymerase chain reaction technique used today—a time-intensive process that requires multiple cycles of heating and cooling blood samples—the compact instrument uses a new DNA amplification method called loop-mediated isothermal amplification. This method uses a portion of DNA polymerase protein, an enzyme that splits the double strand of DNA and allows it to be copied at a single temperature, saving precious time. The multichannel prototype can run a synchronized test for all five pathogens in the blood sample within one hour.

In 2005, emergency response efforts in New Orleans following Hurricane Katrina demonstrated the basic feasibility of POCT. However, according to Nam Tran, associate director of the Center for POC Technologies at the UC Davis Medical Center, follow-up laboratory experiments showed that current testing equipment is not adequate for field use by first responders.

 Rescues were impeded during the Katrina response because hospitals were out of commission and doctors did not have adequate tools for making fast diagnoses. Consequently, treatment was delayed. “Our preliminary survey work following Hurricane Katrina found disaster responders lacked evidence-based methods to diagnose and treat bloodstream infections,” says Tran. “Bringing rapid pathogen nucleic-acid recognition technologies to the point of care will accelerate treatment decisions and potentially improve outcomes.”

Previous Livermore-developed biodetection technologies—including the Autonomous Pathogen Detection System for protection against bioterrorism—will provide some of the foundational technologies for the new POCT instruments, according to chemical engineer John Dzenitis, who is leading the effort at Livermore. “Many of the techniques we use to detect bioterrorism can be adapted to detect blood-borne pathogens,” says Dzenitis. “Before beginning this project, we had a good starting point in bioinformatics research, including tools for designing DNA tests, procedures for screening and optimizing the tests, and instrumentation to automate the process.”

“The goal is to drive the development of appropriate point-of-care diagnostic technologies through collaborative efforts that simultaneously merge scientific and technological capabilities with clinical need,” says Korte. In the field, the need for rapid and accurate diagnosis of infectious disease is critical, given the dependence of therapeutic choices on pathogen identification and the time-consuming nature of alternate approaches.

 The team plans to eventually develop an instrument capable of testing several blood samples at once. Initial tests have already begun at Livermore on bovine whole blood spiked with bacterial DNA and live bacterial cells. Future plans include testing similarly spiked human whole-blood samples on the POCT instruments at the UC Davis Medical Center. These tests, expected to begin this year, will use whole blood from patient volunteers who are suspected of having a blood infection.

POCT devices also could be adapted to test for other types of pathogens, according to Dzenitis. “With a tweak in design, our device could be used to detect influenza viruses, or it could be used to test for certain types of DNA to determine if someone is predisposed to conditions such as Parkinson’s or diabetes,” he says. Whatever its purpose, one thing is certain—the POCT device has the potential to better prepare the nation for future disasters and enhance patient survival outcomes through rapid decision making at both hospital bedsides and in emergency field operations.

Kristen Light is a writer at Lawrence Livermore National Laboratory.