It’s an irony of our time that checking into a hospital can kill you, thanks to several antibiotic-resistant superbugs that have found niches in health-care facilities. Now, to combat the menace of one particularly lethal strain of bacteria, doctors at four hospitals in the United States are trying out a speedy method to identify patients who have MRSA (methicillin-resistant Staphylococcus aureus).
Using a lab-on-a-chip technology from a start-up called F Cubed, physicians should be able to diagnose MRSA within an hour, and without leaving the emergency room. F Cubed hopes that this year’s clinical trial will lead to a commercial device.
MRSA infections start on the skin or in a wound, but they can spread through the bloodstream to cause life-threatening illnesses like pneumonia and sepsis. The U.S. Centers for Disease Control recently estimated that more than 80 000 people got invasive MRSA infections in 2011, and more than 11 000 of those patients died. Most of those serious infections, says the CDC, occurred during or soon after inpatient medical care.
Les Ivie, president and CEO of F Cubed, which is in South Bend, Ind., says that despite the pressing need, doctors lack a quick and easy test to diagnose MRSA. The fastest lab tests today take many hours, and they’re so expensive that physicians rarely opt for them. “If you were to check into a hospital with a suspected infection, typically they would do a plate culture to grow bacteria, and that takes three to four days,” he says. “The problem is that if you have a MRSA infection, you may not have three to four days before it gets into your bloodstream.”
The heart of the F Cubed system is a disposable biochip measuring 7 by 14 millimeters, which snaps into a molded plastic panel that handles the sample flow and waste. The biochip is based on research by Hsueh-Chia Chang, director of the Center for Microfluidics and Medical Diagnostics at the University of Notre Dame, in Indiana. The plastic panel is inside a suitcaselike container along with the components that manage the rest of the testing process, from sample preparation to the final readout.
The device first isolates the DNA in a pus sample from a wound and breaks apart the DNA’s double helix structure into two single strands. Then a pump sends that DNA through the chip’s nanofluidic channel, where minuscule probes hold single strands of DNA unique to the MRSA bacterium. Electrode microarrays on the sides of the chip create an electric field throughout the channel. If MRSA is present in the patient’s body, the DNA in the sample will bind to the complementary DNA on the probes, changing the conductivity of the system. If the biochip detects that change, that means the MRSA bug is present in the sample.
Ivie says this system is cheap to manufacture because, unlike many other genetics-based tests, it doesn’t use any fluorescence or optics. “All we are doing is measuring electrical changes, which is very simple to do,” he says. Another advantage, Ivie says, is ease of use. Other lab tests require technicians to isolate the DNA of just one species in the sample and are vulnerable to contamination, but the F Cubed system works even if the DNA of multiple microbe species is in the mix; the biochip will register the MRSA bacterium’s DNA if it’s present, and the rest will just wash through the channel and out of the chip. “Our process could be done by a physician in an emergency room, in the back of a truck, or in the middle of the desert,” Ivie says. “It does not have to be clean.”
This technology could be a great boon in emergency rooms, says Richard Wenzel, a physician at the Virginia Commonwealth University and an expert on MRSA prevention and treatment in hospitals. “If the patient has actual pus somewhere and you could know within an hour whether this really is MRSA and should be treated appropriately, that would be very useful,” he says. However, Wenzel says, because of increased vigilance by hospital staff, few MRSA patients go untreated today. “What we’re doing now is just treating all skin and soft tissue infections like MRSA, because in 70 to 75 percent of the cases that’s what they turn out to be,” he says. “That would be the caveat to saying this diagnostic tool is a major breakthrough.”
This article originally appeared in print as “Biochip Vs Superbug.”