ARS | Publication request: Colonization of a Newly Constructed Commercial Chicken Further Processing Plant with Listeria monocytogenes

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 19, 2009
Publication Date: February 2, 2010
Citation: Berrang, M.E., Meinersmann, R.J., Frank, J.F., Ladely, S.R. 2010. Colonization of a Newly Constructed Commercial Chicken Further Processing Plant with Listeria monocytogenes. Journal of Food Protection. 73(2):286-291.

Interpretive Summary: Listeria monocytogenes is a human pathogen that can cause a deadly food borne illness. This organism has been associated with poultry meat and fully cooked ready-to-eat (RTE) meat products. It is unclear how commercial chicken cooking plants which produce RTE meat become contaminated with this organism. We examined a large newly constructed commercial chicken cooking plant for the presence of L. monocytogenes. Initially, there was no L. monocytogenes in the plant, but after 1 month of processing, we were able to isolate this bacterium. No L. monocytogenes was detected in the incoming air or was associated with personnel or community samples. One subtype of L. monocytogenes was found in a nearby stream, but not in the plant. The only consistent source of L. monocytogenes to the plant was incoming raw poultry meat. Eight distinct subtypes of L. monocytogenes were detected in raw meat, one of which persisted in the plant. One subtype detected repeatedly in a floor drain in the cooked product handling part of the plant was eventually found on fully cooked RTE meat which was then destroyed. Raw poultry meat is an important source of L. monocytogenes to a chicken cooking plant. It is not understood why only some incoming subtypes originating from raw meat are capable of persisting in the plant potentially contaminating RTE product. Research is required that addresses the problem of this pathogen entering poultry cooking plants and the bacterial ecology relative to L. monocytogenes colonizing drains which may serve as reservoirs for this organism.

Technical 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 clean up shift on a roughly 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 four 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. A drain on the cooked side of the plant became persistently colonized with a subtype that was eventually associated with fully cooked product. Poultry further processing plants are likely to become colonized with L. monocytogenes; raw product is an important source of the organism to the plant.