Rapid diagnostic test for deadly tropical disease

Researchers from James Cook University (JCU) and The Townsville Hospital have developed a highly sensitive and rapid multiplex diagnostic test for melioidosis. Their findings have been published in the journal Diagnostic Microbiology and Infectious Diseases.

Melioidosis is caused by the multidrug-resistant bacterium Burkholderia pseudomallei, which is endemic in northern Australia and is also listed as a potential bioterror agent. The disease particularly affects people in tropical regions of Australia such as Townsville and Darwin.

Melioidosis has a high mortality rate - from 16% in northern Australia to 40% in northeast Thailand - in part because it is difficult to diagnose. The researchers explained, “The gold standard for diagnosis is culture, which requires at least 3-4 days before obtaining a result, hindering successful treatment of acute disease.”

The alternative method, they said, is an indirect haemagglutination assay (IHA), with the result of its low sensitivity being that “approximately half of patients later confirmed culture positive are not diagnosed at presentation and a subset of patients are persistently seronegative”.

The researchers have developed two serological assays - an enzyme-linked immunosorbent assay (ELISA) and a 2-dimensional immunoarray (2DIA). Lead researcher Associate Professor Patrick Schaeffer, from JCU’s Supramolecular and Synthetic Biology Group, said the 2DIA test “works by detecting a subset of specific antibodies that are released in the blood of all patients infected by the bacterium”.

The tests are described by the researchers as “rapid and reliable”.

“Currently, the 2DIA has a sensitivity and specificity of 100% and 87.1%, respectively, with 100% of culture-positive, IHA-negative samples detected. The ELISA has a sensitivity and specificity of 86.2% and 93.5%, respectively, detecting 67% of culture-positive, IHA-negative samples,” they said.

Associate Professor Schaeffer said the researchers are “now in the process of translating the technology into a rapid lifesaving bedside test”.