Colonization of a Newly Constructed Commercial Chicken Further Processing Plant with Listeria monocytogenes†

Abstract

This study was undertaken to determine potential sources of Listeria monocytogenes in a newly constructed chicken further processing plant and document the eventual colonization of the facility by this pathogen. To ascertain the colonization status of the plant, floor drains were sampled after a production shift and again after a cleanup shift on roughly a monthly basis for 21 months. Potential sources of L. monocytogenes to the plant included incoming raw meat, incoming fresh air, and personnel. Nearby environment and community samples were also examined. All L. monocytogenes detected were subjected to DNA sequence–based subtyping. L. monocytogenes was not detected in the plant before the commencement of processing operations. Within 4 months, several subtypes of L. monocytogenes were detected in floor drains, both before and after cleaning and sanitizing operations. No L. monocytogenes was detected on filters for incoming air, samples associated with plant employees, or a nearby discount shopping center. One subtype of L. monocytogenes was detected in a natural stream near the plant; however, this subtype was never detected inside the plant. Eight subtypes of L. monocytogenes were detected in raw meat staged for further processing; one of the raw meat subtypes was indistinguishable from a persistent drain subtype recovered after cleaning on eight occasions in four different drains. Poultry further processing plants are likely to become colonized with L. monocytogenes; raw product is an important source of the organism to the plant.