New method helps faster detection of pathogens in lungs

Scientists have developed a new method that may help detect pathogens which cause tuberculosis in the lungs in just two days.

Time-consuming bacteria cultures, which takes several weeks, no longer need to be taken from the patient samples, meaning that a suitable therapy can be started quickly, according to researchers from University of Zurich (UZH) in Switzerland. Mycobacteria cause various illnesses. Mycobacterium tuberculosis, the main representative of this genus, is the causative agent of tuberculosis, which killed around 1.5 million people worldwide in 2014, researchers said.

Nontuberculous mycobacteria can trigger pulmonary infections, lymph node infections and skin diseases in patients with compromised immune systems, they said. On account of more and more people with chronic lung diseases and the success of transplants, these difficult-to-treat infections have been on the rise continuously in recent decades.

Researchers used a large-scale study with more than 6,800 patient samples to examine molecular-based methods for the detection of mycobacterial pathogens. Because many mycobacteria only grow at a very slow pace, routine detection using bacteria cultures in highly specialised and expensive high-safety labs takes several weeks to complete, researchers said.

The subsequent susceptibility test to determine the appropriate medicine also takes one to two weeks, they said. “For patients and doctors, this long waiting period is an unnecessary test of their patience,” said Peter Keller from UZH.

“By comparison, with molecular detection methods, most patients know after one or two days whether they have an infection with tuberculosis pathogens or with nontuberculous mycobacteria,” he said. For the study, researchers developed a diagnostic algorithm to detect mycobacteria directly from the patient sample using genetic analysis.

With this ultra-fast molecular detection method, the patient samples were examined continuously over three years and compared with the results from the bacteria cultures for more than 3,000 patients, researchers said.

The new molecular-based methods were found to be just as accurate as the lengthy culture-based techniques used to date. In addition, the molecular analysis makes it possible for the first time to also detect the nontuberculous mycobacteria directly from the patient sample within just a few hours.

This means that suitable therapeutic measures can be initiated much more quickly, researchers said. By contrast, if the patient has a tuberculosis infection, a further molecular assay is carried out to test susceptibility to the main tuberculosis drugs “rifampicin” and “isoniazid”, they said.