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Novel holographic microscopy technique rapidly identifies bacteria
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A new microscopy technique that creates holographic images from bacteria may be more efficient than culturing and other traditional methods for identifying bacteria, according to research published in Optics Express.
“Rapid and accurate identification of bacterial species is crucial for diagnosing infectious diseases or screening for poisoning sources in food,” YongKeun Park, PhD, of the Korea Advanced Institute of Science and Technology, Daejeon, South Korea, and colleagues wrote. “Bacterial infection causes a number of severe diseases and syndromes that all require immediate and appropriate treatment based on the detection and identification of the bacterial species.”
The novel method for identifying bacteria involves shooting laser light onto individual bacteria under a microscope to create holographic images. Bacteria is then classified using a mathematical function called a Fourier Transform and specially designed sorting software, which is similar to what computers use for facial recognition, according to a press release.
“Employing laser holographic techniques, we achieved rapid and label-free identification of bacterial species at the single bacterium level with a single-shot measurement,” Park said in the release. “This means the present method can be utilized as a prescreening test for point-of-care bacterial diagnosis for various applications including medicine and food hygiene.”
Blood culturing and real-time quantitative PCR (qPCR) typing are effective at identifying bacteria but they can take up to days and be cost-prohibitive, according to the investigators. The method introduced by Park and colleagues can identify individual bacteria more efficiently and with accuracy greater than 94%, they wrote.
“We have also developed a compact portable device, [the] so-called quantitative phase imaging unit, to convert a simple existing microscope to a holographic one ... which can then be used to identify bacteria species for rural areas and developing countries,” Park said. “Our team has plans to go to Tanzania next month for a field test.” – by David Jwanier
Disclosure: Jo acknowledges support from KAIST Presidential Fellowship and SPIE Optics & Photonics Education Scholarship.
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Nabin K. Shrestha, MD, MPH
Jo and colleagues describe a proof-of-concept study that examined a rapid method for identifying bacteria using a technique of Fourier Transform Light Scattering (FTLS). This method allows for identification of bacteria based on differences in light scattering produced by the various bacteria. The researchers were able to rapidly and accurately distinguish between four different species of rod-shaped bacteria. This is an interesting technique and the speed of the test is a big advantage over currently available methods of microbial identification.
A substantial amount of research is still necessary before the potential for clinical utility of this technique can be recognized. The test will have to demonstrate an ability to identify a large number of pathogenic microorganisms. The test will also have to be accurate across a wide range of concentrations of the microorganisms that could be encountered in clinical practice. It also has to show that the presence of human fluid or tissue does not interfere with the accuracy of the identification. The FTLS method does not involve microbial amplification, so it cannot by itself replace cultures or PCR, which are technologies that amplify the quantity of microorganisms or microbial nucleic acid, allowing for detection and identification of small numbers of microorganisms.
In clinical practice, it is often necessary to perform antimicrobial susceptibility testing in addition to identifying microorganisms. If this technique can live up to its promise of rapidly identifying microorganisms, it will be necessary to determine how it can fit into the clinical workflow where microbial identification accomplishes only part of what is required from microbial testing.
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