Fast-track walking pneumonia test: SERS speeds up diagnosis

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  • Published: Jan 5, 2011
  • Author: David Bradley
  • Channels: Raman
thumbnail image: Fast-track walking pneumonia test: SERS speeds up diagnosis

SERS against pneumonia

A new approach to testing for a common form of pneumonia using nanorod arrays to boost SERS signals can cut the time to diagnosis from several days to a mere ten minutes, according to research published in the journal Plos One.

Mycoplasma pneumoniae is a very small bacterium in the class Mollicutes, it was originally known as the Eaton agent and its small size meant it was not identified as a bacterium for many years because it slipped through standard filter tests used by researchers. As such, science focused on the possibility of the pathogen being a virus until the 1960s, Robert Chanock, a paediatric virologist at the US National Institutes of Health, and colleagues, isolated and cultivated the causative agent of primary atypical pneumonia (the Eaton Agent). They correctly identified the causative agent, not as a virus, but as a mycoplasma and named it Mycoplasma pneumoniae. The Eaton agent can be cultivated well in cell-free media, which opened up research into this common form of bacterial pneumonia, also known as walking pneumonia. Of course, much of the research has focused on improving the diagnosis and treatment of the disease, given the lack of a rapid and reliable diagnostic test and that conventional antibiotics fail to attack it.

Duncan Krause, a professor in the department of microbiology in the University of Georgia Franklin College of Arts and Sciences and his colleagues have now developed a diagnostic test for walking pneumonia based on a nanotechnology platform for surface-enhanced Raman spectroscopy validated the test against true clinical samples with more than 97 percent accuracy.

Positive identification

"If you can make a positive identification from a ten-minute test, then appropriate antibiotics can be prescribed, limiting both the consequences in that patient and the likelihood that it will spread to others," explains Krause, contrasting that response time with the several days during which a patient is not being treated and yet remains infectious.

Krause and his colleagues have extended SERS by using silver nanorod arrays to help them detect the Raman spectroscopic signature at near-infrared wavelengths as a laser scans samples taken by throat swab. Krause's colleague Yiping Zhao, director of the UGA Nanoscale Science and Engineering Center developed the nanorod array, which Krause describes as resembling a brush of tightly packed bristles, with each of the tiny silver rods extending from the surface at a specific angle. Tiny bacteria from a sample intercalate themselves between the "bristles" which then amplify the Raman signal allowing subsequent analysis and identification by a computer program.

"Walking pneumonia feels like a bad chest cold that will not go away," says Krause. The bacterium is a major cause of respiratory disease in humans and the leading cause of pneumonia in older children and young adults. "It can persist for weeks and even months and can cause permanent damage to the lungs if not diagnosed promptly. A delay in diagnosis extends the likelihood of complications as well as continued transmission of the infection to others."

Portability and pathogens

Krause adds that their system might be made small and portable, perhaps on a scale that could fit into a briefcase-sized container. So far, they have only carried out testing in a laboratory setting. "Our hope is that when we begin to explore the capabilities of this technology, it can be applied in point-of-care testing," Krause adds. "Then the impact becomes truly significant." He points out that such interdisciplinary collaboration between nanotechnology experts and scientists working on infectious disease could eventually lead to similar systems for detecting other pathogens in clinical samples quickly and easily. We need to do a thorough job with mycoplasmae first," concedes Krause. "Then we can go to other clinical samples and ask the same questions with other infectious agents."

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

Credit: Krause et al/PLoS ONE A new approach to testing for a common form of pneumonia using nanoparticles to boost SERS signals can cut the time to diagnosis from several days to a mere ten minutes.
Differentiation of spiked and control throat swab samples

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