Tracing Listeria monocytogenes in a Commercial
Chicken Cooking Plant
April 19, 2010
Incoming raw poultry is the primary
source of Listeria monocytogenes contamination in commercial chicken
cooking plants, according to a 21-month study conducted by
Agricultural Research Service (ARS)
scientists and their collaborators at the University of Georgia.
The studys results will help these facilities more sharply focus their
sanitation processes to reduce cross-contamination. L. monocytogenes is
a bacterial human pathogen that is sometimes found in fully cooked,
ready-to-eat processed meat and poultry products.
By testing a brand-new commercial cooking facility before and after
processing began, the research team was able to track sources of contamination.
The research team was led by ARS microbiologist
Berrang of the
Epidemiology and Antimicrobial Resistance Research Unit at the
B. Russell Research Center in Athens, Ga.
Because the pathogen is prevalent in the environment and in various forms,
there were several potential sources of contamination, including employees,
incoming fresh air, raw meat and the surrounding environment.
Potential sources of L. monocytogenes were tested by taking samples
of soil and water around and near the facility exterior, and by testing heavily
traveled floor surfaces following personnel shift changes. Samples were also
collected and tested from incoming air from air vent filters and from monthly
swabs of incoming raw meat. The plant was free of L. monocytogenes when
first constructed; floor drains in the facility were sampled approximately
monthly to determine at what point the plant would become colonized with the
Within four months of operation, L. monocytogenes was detected in
floor drains, indicating that the organism had been introduced from some
outside source. No L. monocytogenes was recovered from any floor samples
in the plant entryways, locker room or cafeteria. Likewise, the organism was
not detected on air vent filters during the survey. The only tested source
found to be consistently positive for L. monocytogenes was incoming raw
Quality assurance in the test plant was exceptional and included an
extensive proactive sampling plan to assure food safety. L.
monocytogenes can become prevalent in food processing environments;
sanitation, biosafety and product sampling protocols are in place in these
facilities to prevent shipping contaminated product.
This research was reported in the Journal
of Food Protection. Co-authors included ARS microbiologist
Meinersmann in Athens, University of Georgia scientist Joseph Frank, and
former ARS researcher Scott Ladely.
ARS is the principal intramural scientific research agency of the
U.S. Department of Agriculture (USDA). The
research supports the USDA priority of ensuring food safety.