New machine slashes pathogen detection times

Researchers have designed a machine that they say will speed up the concentration step of foodborne pathogen detection.

The system, designed by Purdue University researchers, reportedly concentrates foodborne Salmonella and other pathogens faster than conventional methods by using hollow, thread-like fibres that filter out the cells.

The machine - a continuous cell concentration device - could make it possible to routinely analyse 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 professor of biomedical engineering at Purdue University and director of Purdue’s Laboratory of Renewable Resources Engineering (LORRE).

“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.”

The first step in foodborne pathogen detection is concentrating the number of cells in test samples. With the standard method now in commercial use, this typically takes one day. The new method will reduce this time to one hour.

The Purdue research team has published its findings in a research paper which will appear in the journal Applied and Environmental Microbiology. The findings showed the system was able to concentrate inoculated Salmonella by 5000 to 1000 times the original concentration in test samples (this level of concentration is required for accurate detection). Another finding showed the system recovered 70% of the living pathogen cells in samples.

“This is important because if you filter microorganisms and kill them in the process that’s self defeating,” Ladish 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 pre-treated to prevent the filtering membranes from clogging. The fluid is then passed through 12 hollow-fibre 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 Purdue team says the technique could be performed during food processing or vegetable washing before the products are shipped.

Purdue has filed a patent application for the concept.