New tactic may expose stealthy Salmonella
Even the smallest quantity of Salmonella may, in the future, be easily detected with a technology known as SERS, short for “surface-enhanced Raman scattering.” Bosoon Park, Agricultural Engineer with the U.S. Dept. of Agriculture’s Agricultural Research Service (USDA ARS), is leading exploratory studies of this analytical technique’s potential for quick, easy, and reliable detection of Salmonella and other foodborne pathogens.
In a SERS analysis, a specimen is placed on a surface, such as a stainless steel plate, that has been “enhanced” or changed from smooth to rough. For some of their research, Park’s team enhanced the surface of stainless steel plates by coating them with tiny spheres, made up of a biopolymer encapsulated with nanoparticles of silver. Rough surfaces, and colloidal metals such as silver, can enhance the scattering of light that occurs when a specimen, placed on this “nanosubstrate,” is scanned with the Raman spectrometer’s laser beam.
The scattered light that comes back to the spectroscope forms a distinct spectral pattern known as a Raman spectral signature, or Raman scattered signal. Researchers expect to prove the concept that all molecules, such as those that make up Salmonella, have their own unique Raman spectral signature.
In work with comparatively large concentrations of two different kinds, or serotypes, of Salmonella enterica—Enteritidis and Typhimurium—Park’s tests showed that SERS can differentiate between these two serotypes. With further research, SERS may prove optimal for finding very small quantities of bacteria in a complex, real-world background, such as a food or beverage sample, Park notes.
