Nanotechnology, biochips detect bacteria.

Scientists from the USDA and Purdue University (Department of Biomedical Engineering, 1296 Potter Building, West Lafayette, IN 47907) are collaborating to develop faster, more precise ways to improve product safety. With research grants and a partnership with the ARS, Purdue has launched the Center for Food Safety Engineering, which is focusing on developing methods to find, identify and eradicate microbes or chemicals.

The Centers for Disease Control and Prevention (CDC) estimates that 76 million cases of foodborne illness occur in the United States annually, claiming approximately 5,000 lives and costing $7.7 billion or more. Foodborne pathogens cause 325,000 hospitalizations yearly, according to the CDC.

One aspect of the task with which researchers must cope is the difficulty of tracing the source of foodborne illness. In addition, a minuscule amount of some pathogens, such as Listeria, can cause illness. So the center's scientists are investigating detection methods that not only are faster and more exact, but which also require smaller samples in order to make an analysis.

There are a variety of projects underway at the center. Fusarium is a fungus that infests grains and then produces carcinogenic mycotoxins that can affect both people and animals. It often appears in moldy corn, but also has been found in sorghum, rice, cottonseed meal, legumes, wheat and barley. Researchers are working on a method to detect various fusarium species in grain and foods. This effort may give grain storage operators information enabling them to alter storage conditions in order to prevent fusarium growth.

Nanotechnology and magnetic beads are integral to investigations by scientists as they develop more sensitive, less expensive and faster ways to detect Listeria. Listeria is responsible for about 2,500 cases of foodborne diseases each year. In the first of a two-step method, microscopic beads separate Listeria cells from food. Then the researchers Zuse a cytotoxicity assay that differentiates between disease-causing Listeria cells and those that are harmless.

Other scientists are fabricating and designing microscopic, hair-thin structures that will carry fluid from a food sample across a biochip. The chip will electronically detect Listeria and distinguish it from other organisms. Molecules on the chip target and capture the Listeria. When the targeted microorganism is captured, an electrical response from the biochip will signal its presence.

Yet others are developing ways to rapidly and accurately detect PCBs in fish. They're also investigating a rapid test for predicting the toxicity of PCBs in fish. Measuring the characteristics of light scattered across a surface is another way to quickly detect and identify biological contaminants and distinguish between virulent and non-virulent bacteria. Using a scatterometer, scientists detected bacterial pathogens as early as 6 to 10 hours after they were introduced into food.

Certain viruses called bacteriophages attack only specific bacteria. Using that knowledge, researchers are genetically engineering bacteriophages that detect and identify specific bacterial pathogens. When bacteriophages infect the target pathogen, they cause it to produce a signal compound. The compound triggers a bioluminescent chain reaction in a second type of bacteria, causing it to glow. This indicates the presence of pathogens. Eventually this two-component detection system will include use of a hand-held luminometer that would enable those in the field to test for bacteria.

Further information. Michael Ladisch; phone: [phone]; fax: [phone]; email: [e-mail].