The new “continuous cell concentration device” utilises a technique called cross-flow microfiltration to concentrate bacterial cells. A food homogenate is chemically pre-treated and pre-filtered to break down and remove larger particles that might cause clogging, before being passed through a polysulfone hollow fibre membrane module with a nominal pore size of 0.2µm. The homogenate circulates within the system achieving a 500- to 1,000-fold concentration of inoculated Salmonella cells and a 70% recovery rate in 35 to 45 minutes.
The Purdue researchers say that the system can quantify as few as 10 viable cells per ml of homogenate, which translates to 100 cells per gram of chicken or other food samples. They suggest that the system could be used to detect foodborne pathogens in six hours or less without the need for overnight enrichment cultures.
A report of the method will be published in a forthcoming issue of the journal Food and Environmental Microbiology and more information plus an abstract can be found here.