Isolation and identification of Listeria monocytogenes utilizing DC insulator-based dielectrophoresis.

Foodborne pathogens pose one of the greatest challenges facing public health in the modern day. One important pathogen, Listeria monocytogenes, is known to be challenging to detect and identify. Three serovars cause most of the Listeria related food-borne illnesses, which the Centers for Disease Control currently utilizes a combination of pulsed-field gel electrophoresis and whole genome sequencing for identification and the determination of clusters and outbreaks. There is a potential method for rapid collection of epidemiological information by exploiting the electrokinetic and dielectrophoretic properties of the L. monocytogenes serovars. Using dielectrophoresis, the three most commonly identified serovars of L. monocytogenes can be distinguished from each other. The electrokinetic and dielectrophoretic mobilities of each serovar was determined through a combination of electrokinetic velocity and dielectrophoretic trapping assessments, in conjunction with finite element multi-physics modeling. A mathematical model of the data, which defines the various factors of dielectrophoretic trapping, is utilized and verified based on the behavior of L. monocytogenes in the microchannel. The trapping condition for the serovars were evaluated as 2.8±0.2×109, 2.2±0.2×109, and 2.2±0.3×109Vm-2 and the electrokinetic mobility was assessed to be 19±0.7, 17±0.7, and for the L. monocytogenes serovars 1/2a, 1/2b, and 4b, respectively.

Differentiation of Escherichia coli serotypes using DC gradient insulator dielectrophoresis.

Bacteria play a significant role in both human health and disease. An estimated 9.4 million cases of foodborne illness occur in the United States each year. As a result, rapid identification and characterization of microorganisms remains an important research objective. Despite limitations, selective culturing retains a central role among a cadre of identification strategies. For the past decade, separations-based approaches to rapid bacterial identification have been under investigation. Gradient insulator dielectrophoresis (g-iDEP) promises benefits in the form of rapid and specific separation of very similar bacteria, including serotypes of a single species. Furthermore, this approach allows simultaneous concentration of analyte, facilitating detection and downstream analysis. Differentiation of three serotypes or strains of Escherichia coli bacteria is demonstrated within a single g-iDEP microchannel, based on their characteristic electrokinetic properties. Whole cells were captured and concentrated using a range of applied potentials, which generated average electric fields between 160 and 470 V/cm. Bacteria remained viable after exposure to these fields, as determined by cellular motility. These results indicate the potential g-iDEP holds in terms of both separatory power and the possibility for diagnostic applications.