Holographic Microscopy Identifies Single Bacterium at Point of Care

Rapid point of care identification of bacterial infections remains an elusive goal in many instances, with labs around the world relying on culturing that can take days. The other option is for path labs to employ real-time polymerase chain reaction that can be too expensive for many clinics. Now researchers at the Korea Advanced Institute of Science and Technology (KAIST) report in journal Optics Express on a new microscopy technique that can identify the strain of a bacterial pathogen from a single example of the microorganism.

The team built a device they call quantitative phase imaging unit (QPIU) that converts a traditional microscope into one capable of doing microscopic holography. The new imaging technique relies on illuminating the bacterium with laser light and analyzing the resulting hologram using special computer algorithms. The holograms are processed using Fourier transforms and then compared to previously acquired scans of known bacteria. The team tested their approach on four visually nearly identical rod-shaped bacteria, three of which are responsible for disease and one that’s benign. They showed that while it’s nearly impossible to differentiate them using standard microscopy, their new method was very effective at identifying which is which.

The researchers are now planning a trip to Tanzania next month to field test the technology in a real-world setting where it will be particularly beneficial.

Some details from the study abstract:

In order to achieve rapid and label-free identification of bacterial species at the single bacterium level, we propose and experimentally demonstrate an optical method based on Fourier transform light scattering (FTLS) measurements and statistical classification. For individual rod-shaped bacteria belonging to four bacterial species (Listeria monocytogenes, Escherichia coli, Lactobacillus casei, and Bacillus subtilis), two-dimensional angle-resolved light scattering maps are precisely measured using FTLS technique. The scattering maps are then systematically analyzed, employing statistical classification in order to extract the unique fingerprint patterns for each species, so that a new unidentified bacterium can be identified by a single light scattering measurement. The single-bacterial and label-free nature of our method suggests wide applicability for rapid point-of-care bacterial diagnosis.

Study in Optics Express: Label-free identification of individual bacteria using Fourier transform light scattering…