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Test finds E. coli in beef faster.

In Brief: Infrared spectroscopy can detect E. coli faster than current testing methods and can cut days off investigations of outbreaks, according to a study at Purdue University.

Lisa Mauer, an associate professor of food science, detected E. coli in ground beef in one hour using Fourier transform infrared spectroscopy--in much less time than the 48 hours required for conventional plating technology, which requires culturing cells in a laboratory. Mauer said spectroscopy could be done in the same laboratories, just in much less time. The spectroscopy method also differentiates between strains of E. coli 0157:H7, meaning outbreaks could be tracked more effectively and quickly. Current tests are multi-step and take almost one week to get results.

"Even with all the other bacteria present in ground beef, we could still detect E. coli and recognize different strains," said Mauer.

Mauer demonstrated two methods for separating bacteria from ground beef for testing. An antibody-capture method, which binds bacteria to antibodies attached to magnetic beads, gave results in four hours. A filtration method achieved results in about an hour.

Infrared spectroscopy could detect as little as one E. coli cell if the bacteria were cultured for six hours. Conventional plating techniques used for E. coli detection require culturing cells for 48 hours.

E. coli has a specific infrared spectrum that can be read with a Fourier transform infrared spectrometer. Infrared light is passed over a sample. The spectrometer reads the spectrum created by the combination of energy that has been absorbed and energy that has been reflected back. "Energy is only absorbed by certain components of a sample," Mauer said. "If that component isn't there, the energy is reflected back."

Mauer's testing methods also can differentiate between living and dead E. coli cells, something current testing methods cannot do. "If the cells are dead, they're not harmful, but the presence of that dead population could tell you something about the quality of the product," Mauer said.

For more information, contact Brian Wallheimer, bwallhei@purdue.edu, or Lisa. Mauer, mauerl@purdue.edu.
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Title Annotation:update
Publication:Resource: Engineering & Technology for a Sustainable World
Date:Nov 1, 2010
Words:339
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