A team of researchers from the Korean Advanced Institute of Science and Technology (KAIST) in Daejeon, South Korea have developed a new optical method that is said to be capable of identifying bacterial species at the single bacterium level.
The new method works by directing a laser onto bacterial cells under a modified microscope to create a holographic image, or “two-dimensional angle-resolved light scattering map”, which can be precisely measured using a Fourier transform light scattering (FTLS) technique. The result is then analysed by computer software containing a machine-learning algorithm and statistically classified to produce a unique optical fingerprint for each bacterial species.
The KAIST researchers have so far tested their method on four bacterial species, Listeria monocytogenes, E. coli, Lactobacillus casei and Bacillus subtilis. The results to date show that the four species could be identified with greater than 94% accuracy. The next phase of the work will investigate whether the method can distinguish pathogenic subgroups from harmless ones within the same species.
While the principal application for the technology is expected to be clinical microbiology, the ability to identify a single cell under the microscope makes it potentially very useful for rapidly detecting and identifying foodborne pathogens too.
The researchers have also developed a compact portable device called a quantitative phase imaging unit that can be used to convert a basic light microscope into a holographic instrument. This could allow the method to be used to identify bacteria in the field, in developing countries and in smaller labs.
The method is described in a paper published in the journal Optics Express, which can be found in full here.