LISTERIA MONOCYTOGENES IS A PATHOGEN COMMONLY ASSOCIATED WITH READY-TO-EAT FOODS, SUCH AS DELI MEATS AND CHEESES. L. MONOCYTOGENES CAN SURVIVE AND PERSIST WITHIN THE ENVIRONMENT IN FOOD PROCESSING AND RETAIL FACILITIES, OFTEN FOUND IN LOCATIONS SUCH AS DRAINS, FLOOR-WALL JUNCTURES, AND IN SINKS; THERE IS A HIGH RISK OF CROSS-CONTAMINATION FROM THESE NICHES TO FOOD CONTACT SURFACES, AND ULTIMATELY TO THE PRODUCT. IT IS LIKELY THAT OTHER BACTERIA SURVIVING WITH L. MONOCYTOGENES IN THESE SITES ARE PROTECTING THE PATHOGEN FROM CURRENT CLEANING AND SANITATION MEASURES, ALLOWING THE PATHOGEN TO PERSIST IN THESE FACILITIES. THIS STUDY WILL UTILIZE TECHNOLOGIES TO SEQUENCE THE DNA OF THE ENTIRE COMMUNITY OF BACTERIA FROM THREE SITES IN TEN RETAIL DELI DEPARTMENTS ACROSS THE UNITED STATES. THESE SEQUENCES WILL BE USED TO IDENTIFY WHICH MICROORGANISMS ARE PRESENT IN SPECIFIC SITES WITH L. MONOCYTOGENES AND IF THERE ARE ANY BACTERIAL SPECIES THAT CAN PREDICT THE PRESENCE OF L. MONOCYTOGENES. THIS INFORMATION WILL BE USEFUL TO RETAILERS TO DETERMINE IF NEW CLEANING AND SANITATION PRACTICES CAN BE DESIGNED TO TARGET OTHER MICROORGANISMS THAT HELP L. MONOCYTOGENES PERSIST IN THESE LOCATIONS, RATHER THAN TARGETING THE PATHOGEN ITSELF. IF THERE ARE OTHER MICROORGANISMS THAT CAN PREDICT THE PRESENCE OF L. MONOCYTOGENES AND CAN BE REMOVED BY CLEANING AND SANITATION, THIS MAY DISRUPT THE ENVIRONMENT THAT ALLOWS THE PATHOGEN TO SURVIVE, THUS MAKING THE PATHOGEN MORE VULNERABLE TO CLEANING PROTOCOLS.