A handheld diagnostic device that researchers at Massachusetts General Hospital, Boston, first developed to diagnose cancer has been adapted to rapidly diagnose tuberculosis (TB) and other important infectious bacteria. The portable device combines microfluidic technology with nuclear magnetic resonance (NMR) to not only diagnose these important infections but also determine the presence of antibiotic-resistant bacterial strains.
"Rapidly identifying the pathogen responsible for an infection and testing for the presence of resistance are critical not only for diagnosis but also for deciding which antibiotics to give a patient," says Ralph Weissleder, MD, PhD, director of the MGH Center for Systems Biology. "These described methods allow us to do this in two to three hours, a vast improvement over standard culturing practice, which can take as much as two weeks to provide a diagnosis."
The system detects DNA from the tuberculosis bacteria in small sputum samples. After DNA is extracted from the sample, any of the target sequence that is present is amplified using a standard procedure, then captured by polymer beads containing complementary nucleic acid sequences and labeled with magnetic nanoparticles with sequences that bind to other portions of the target DNA. The miniature NMR coil incorporated into the small device, about the size of a standard laboratory slide, detects any TB bacterial DNA present in the sample.
Tests of the device on samples from patients known to have TB and from healthy controls identified all positive samples with no false positives in less than three hours.
