Impedance spectroscopy and biochip sensor for detection of Listeria monocytogenes

Listeria monocytogenes is a deadly foodborne human pathogen. Its ubiquitous nature and its ability to grow at refrigeration temperatures makes this organism a difficult one to control. High-volume processing of food products and poor sanitary conditions of the processing plants often allow this organism to be present in processed, ready-to-eat (RTE) foods. Improved processing along with real time detection could reduce the incidence of this pathogen. Conventional methods can detect this pathogen accurately, but take several days (2-7d) to complete, which is not practical considering the short shelf-life and cost of storage of RTE foods. Biosensor based approaches were adopted for sensitive detection of Listeria. Antibody-coupled fiber optic and microelectrical-mechanical system (MEMS) biochips were designed and examined for direct detection of L. monocytogenes from liquid samples. Also, interdigitated microsensor electrode (IME) chip and spectrofluorometer were used to measure L. monocytogenes interaction with mammalian cells (cytopathogenic activities) for indirect detection. Preliminary data generated using laboratory cultures of Listeria species indicated that L. monocytogenes could be detected in 30 min to 1 h 30 min depending on the techniques used.