WEST LAFAYETTE, Ind. — Researchers have developed a system
that concentrates foodborne salmonella and other pathogens faster than
conventional methods by using hollow thread-like fibers that filter out the
cells, representing a potential new tool for speedier detection.
The machine, called a continuous cell concentration device,
could make it possible to routinely analyze food or water samples to screen for
pathogens within a single work shift at food processing plants.
“This approach begins to address the critical need for the
food industry for detecting food pathogens within six hours or less,” said
Michael Ladisch, a distinguished professor of agricultural and biological
engineering at Purdue University. “Ideally, you want to detect foodborne
pathogens in one work shift, from start to finish, which means extracting the
sample, concentrating the cells and detection.”
A report from the Centers for Disease Control and Prevention
indicates a lack of recent progress in reducing foodborne infections and
highlights the need for improved prevention. Although many foodborne illnesses
have declined in the past 15 years, the number of laboratory-confirmed
salmonella cases did not change significantly in 2012 compared with 2006 to
The first step in detecting foodborne pathogens is
concentrating the number of cells in test samples. The new system enables
researchers to carry out the concentration step within one hour, compared to a
day for the standard method now in commercial use, said Ladisch, also a
professor of biomedical engineering and director of Purdue’s Laboratory of
Renewable Resources Engineering.
Findings are detailed in a research paper to appear in
November in the journal Applied and
Environmental Microbiology .
The paper was authored by doctoral student Xuan Li; LORRE
research scientist Eduardo Ximenes; postdoctoral research associate Mary Anne
Roshni Amalaradjou; undergraduate student Hunter B. Vibbert; senior research
engineer Kirk Foster; engineering resources manager Jim Jones; microbiologist
Xingya Liu; Arun K. Bhunia, a professor of food microbiology; and
Findings showed the system was able to concentrate
inoculated salmonella by 500 to 1,000 times the original concentration in test
samples. This level of concentration is required for accurate detection.
Another finding showed the system recovered 70 percent of
the living pathogen cells in samples, Ladisch said.
“This is important because if you filter microorganisms and
kill them in the process that’s self-defeating,” he said. “The goal is to find
out how many living microorganisms are present.”
The machine was used to concentrate cells in a sample of
chicken meat. The sample is first broken down into the consistency of a
milkshake and chemically pretreated to prevent the filtering membranes from
The fluid is then passed through 12 hollow-fiber filters
about 300 microns in diameter that are contained in a tube about the size of a
cocktail straw. The filtering process continues until pathogens if present are
concentrated enough to be detected.
The technique, developed by researchers from Purdue’s
colleges of Engineering and Agriculture, could be performed during food
processing or vegetable washing before the products are shipped.
The U.S. Department of Agriculture will test the system,
which is not yet ready for commercialization.
One feature that could make the machine practical for
commercial application is that it can be quickly cleaned between uses. The tubes
are flushed with sodium hydroxide and alcohol.
Purdue has filed a patent application for the
The research is funded by the U.S. Department of
Agriculture, Purdue’s Agricultural Research Programs and Center for Food Safety
Engineering, and the Department of Agricultural and Biological Engineering.