Researchers at Purdue University have developed a new low-cost system that analyzes scattered laser light to quickly identify bacteria for applications in medicine, food processing and homeland security at one-tenth the cost of conventional technologies.

The technique – Bacteria Rapid Detection Using Optical Scattering Technology – works by shining a laser through a petri dish containing bacterial colonies growing in a nutrient medium.

"Unlike conventional methods, we don’t have to do any biochemical staining, DNA analysis or other types of manipulation," said Bartek Rajwa, a staff scientist at the Bindley Bioscience Center in Purdue’s Discovery Park, the university’s hub for interdisciplinary research.

Particles of light, called photons, bounce off of the colony, and the pattern of scattered light is projected onto a screen behind the petri dish. This "light-scatter pattern" is recorded with a digital camera and analyzed with sophisticated software to identify the types of bacteria growing in colonies. Further work will include research to develop a graphical user interface.

"There are potentially thousands of applications for this new technology, from identifying stem cells to drug-resistant staph infections to pathogens on the battlefield." said J. Paul Robinson, a researcher at the Bindley Center and a professor in the Weldon School of Biomedical Engineering and the School of Veterinary Medicine.

The work was initiated by Arun Bhunia, a professor of food microbiology in the Department of Food Science; and E. Daniel Hirleman, a professor and William E. and Florence E. Perry Head of Purdue’s School of Mechanical Engineering. The research has recently received funding from the USDA through Purdue’s Center for Food Safety Engineering.

Findings are detailed in a research paper appearing this month in the Journal of Biomedical Optics.