New device to rapidly diagnose bacterial infections

Washington: A new device which may shorten the time required to rapidly diagnose bacterial infections from days to hours has been developed by researchers.

The system would allow point-of-care diagnosis, as it does not require the facilities and expertise available only in hospital laboratories, researchers said.

“Rapid and efficient diagnosis of the pathogen is a critical first step in choosing the appropriate antibiotic regimen, and this system could provide that information in a physician’s office in less than two hours,” said Ralph Weissleder from Massachusetts General Hospital (MGH) in the US.

While considered the gold standard for diagnosing bacterial infections, traditional culture-based diagnosis can take several days and requires specialised equipment, trained laboratory personnel and procedures that vary depending on the particular pathogen, researchers said.

Emerging genetic approaches that identify bacterial species by their nucleic acid sequences are powerful but still require complex equipment and workflows, restricting such testing to specialised hospital laboratories, they said.

The system dubbed PAD for Polarisation Anisotropy Diagnostics, allows for accurate genetic testing in a simple device. Bacterial RNA is extracted from a sample in a small, disposable plastic cartridge, researchers said.

Following polymerase chain reaction amplification of the RNA, the material is loaded into a two centimetre plastic cube containing optical components that detect target RNAs based on the response to a light signal of sequence-specific detection
probes, they said.

These optical cubes are placed on an electronic base station that transmits data to a smartphone or computer where the results can be displayed.

For the study, researchers used a prototype PAD system containing four optical cubes to test clinical samples from nine patients and compared the results with those acquired by conventional microbiology cultures.

Testing for the presence of five important bacterial species – E coli, Klebsiella, Acinetobacter, Pseudomonas and Staph aureus – and for factors indicating the virulence and antibiotic resistance of specific strains produced identical results with both procedures, researchers said.

But while PAD provided results in less than two hours, the bacterial culture process took three to five days, they said.

“We can see three immediate applications for a system that can provide such rapid and accurate results – quickly diagnosing a patient’s infection, determining whether antibiotic-resistant bacteria are present in a group of patients, and detecting bacterial contamination of medical devices or patient environments,” said Hakho Lee from MGH. The findings were published in the journal Science Advances.