U.S.D.A. Agricultural Research Service researchers used hyperspectral imaging, which combines digital imaging with spectroscopy, to provide hundreds of individual wavelength measurements for each image pixel, writes the A.R.S.’s Sharon Durham. A.R.S. is the chief scientific research agency of U.S.D.A.
Microorganisms grown on solid media carry unique spectral fingerprints in the specific portion of the electromagnetic spectrum, according to the study. A hyperspectral imager identifies these fingerprints by measuring light waves that bounce off or through these objects.
Hyperspectral imaging, unlike the human eye which sees only visible light, can detect visible light as well as light from the ultraviolet to near-infrared ranges. Hyperspectral imaging may also be applicable to other pathogen detection studies.
Growing Campylobacter directly on solid media has been an effective method to isolate this organism, but distinguishing Campylobacter from non-Campylobacter microorganisms is difficult because different bacteria can often look very similar, Durham writes.
A research team led by A.R.S. electronics engineer Seung-Chul Yoon, at the agency's Quality and Safety Assessment Research Unit in Athens, Ga., developed the imaging technique to detect Campylobacter colonies on solid media in 24 hours. Normally, isolation and detection for identification of Campylobacter from foods like raw chicken involve time-consuming or complicated laboratory tests that may take several days to a week.
This "sensing" technology, which was nearly 100% accurate with pure cultures of the microorganisms, could be used for early detection of presumptive Campylobacter colonies in mixed cultures. The researchers are working toward developing a presumptive screening technique to detect Salmonella and Campylobacter in food samples.
Findings from this study were published in the journal Sensing and Instrumentation for Food Quality and Safety. This research supports the U.S.D.A. priority of ensuring food safety.