A little-known chronic lung disease is silently emerging as a growing public health threat in the U.S. and around the world. Nontuberculous mycobacteria — a group of 200 known environmental bacteria found in soil and water, including household plumbing — can cause chronic, tuberculosis-like lung infections. NTM lung disease afflicts as many as 300,000 Americans a year.
Now, researchers at Tulane University have developed a new diagnostic platform that can identify the precise species of bacteria causing a patient's infection in just a few hours — a dramatic improvement over the current standard, which can take four to six weeks.
"Diagnosing NTM lung disease is very slow, and patients are left with a significant physical and emotional burden because they don't know the answer or what the treatment plan should be," said lead investigator Bo Ning , assistant professor of molecular biology at Tulane University School of Medicine. "Clinicians need a faster test that will allow them to accurately identify the specific type of bacteria that is causing the patient's lung disease."
The team's diagnostic platform, called CANDI or CRISPR-assisted Nanodroplet Differential Identification, was described in a new study published in Science Translational Medicine.
NTM lung disease is closely associated with its more notorious relative, tuberculosis. Symptoms are similar enough that it is often misdiagnosed as TB. The problem is that treatments for TB and NTM lung disease differ significantly, and a misdiagnosis can put patients on an incorrect treatment plan for months. This is particularly concerning for a disease that has a five-year mortality rate approaching 18% and is becoming prevalent enough it outpaces TB infections in many developed countries, including the U.S., England and Japan.
"NTM lung disease is becoming more and more common, and the current detection approach is so difficult that patients end up suffering," Ning said. "This new method will help clinicians get patients started on the right treatment faster."
CANDI uses mucus from the lungs and other respiratory fluids to test for up to 15 clinically relevant species and subspecies of NTM bacteria at once. In a study of 230 clinical samples, the platform correctly identified NTM species and subspecies with 97.3% accuracy.
NTM exists naturally in the environment and typically is of little threat to healthy people. But the infection can hit certain groups much harder — including older adults, those with underlying lung conditions and people with weakened immune systems, such as those undergoing cancer treatment or with HIV.
Trends also point to the disease becoming more prevalent in the South, where cases are already higher than in other parts of the U.S., as rising temperatures and humidity create more favorable conditions for the bacteria.
The test Tulane researchers developed was designed to specifically target NTM infections, but the novelty of the method may allow for expansion into other difficult-to-diagnose diseases.
"Think of this as a platform technology," Ning said. "We can do multiplex bacterial identification for other infections as well."
