Isolation of highly selective phage-displayed oligopeptide probes for detection of listeria monocytogenes in ready-to-eat food

Listeria monocytogenes is the major etiologic agent for foodborne Listeriosis in humans from consumption of readyto- eat (RTE) food. According to Center for Disease Control and Prevention, an estimated 1,600 people contract Listeriosis each year with approximately 260 deaths. This high rate of mortality has alerted the Food Safety Inspection and Services to release the Notice 23-99, Instructions for Verifying the L. monocytogenes Reassessment , on August 3, 1999 for their inspectors. According to the FDA’s Bacterial Analysis Manual Chapter 10, L. monocytogenes in RTE food samples is detected via microbiological culture-based tests, qPCR, pulsed-field gel electrophoresis, and other alternative methods. Unfortunately, these methods are time consuming (48-72 hours) and require dedicated laboratory facility. Thus, to develop a real-time L. monocytogenes biosensor, we isolated L. monocytogenes specific oligopeptides displayed on bacteriophages using modified biopanning procedures. In order to account for major temperature dependent morphological alterations of L. monocytogenes at 4°C versus 37°C, we used bacterial cells adapted to either temperature as the target in our biopanning. To date, we have isolated several candidate probes that can recognize either cold-adapted, warm-adapted L. monocytogenes cells, or both types of bacterial cells. Our isolated probes will be used on the magnetoelastic biosensor platforms for real-time detection of L. monocytogenes in RTE foods stored at 4°C or in samples/fluids for bacterium adapted to human body temperature.