Speeding Up the Concentration Step in Food-Pathogen Detection

One of the most stubborn bottlenecks in rapid detection and identification of foodborne pathogens has long been the very first step: Concentration of enough cells to accurately identify the pathogen. Current standard methods of cell concentration take about 24 hours, but a new method developed by researchers at Purdue University could cut that time to as little as one hour.

Using a dozen tiny, threadlike hollow fibers about 3 microns in diameter, the system—called a continuous cell concentration device—repeatedly filters a test sample, such as chicken parts broken down to a puree, until the pathogens are concentrated enough to be detected.

According to findings published ahead of print in the September 2013 online edition of Applied and Environmental Microbiology, the device can concentrate inoculated Salmonella by 500 to 1,000 times the original concentration, and recovers 70 percent of living pathogen cells in test samples.

The concept isn’t new—microfiltration was first proposed some 30 years ago, says lead researcher Michael Ladisch, PhD, a distinguished professor of agricultural and biological engineering at Purdue. “It appeared to be very simple when we started investigating it, but it turned out a lot of factors interfere with the process. The membranes themselves had to advance to the point where they weren’t plugging very quickly after the filtration was started.”

There are still some hurdles ahead before the system can be broadly adopted. “A key limitation right now is being able to use the membrane repeatedly, because it is expensive,” Dr. Ladisch says. “We are now developing and testing techniques that enable one to clean out the system, and those are looking good.”

The developers are also testing the instrument in another lab outside Purdue, hoping to replicate their findings. “The success of this technique will also depend on the work of our colleagues who are working on pathogen detection,” Dr. Ladisch notes.


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