SPOTLIGHT By Byron D. Chaves, Ph.D., and Mindy M. Brashears, Ph.D.
Mitigation of Listeria monocytogenes in
Ready-to-Eat Meats Using Lactic Acid Bacteria
Nothing like a series of disease outbreaks and food recalls to put a pathogen at the forefront of the media and make processors fear the worst. Listeria monocytogenes has given us a lot
to talk and think about over the last 5 years.
Outbreaks of listeriosis associated with the
consumption of contaminated caramel apples,
ice cream and cantaloupes, as well as several
multi-state recalls of bagged salads, frozen vegetables, school
lunches, frankfurters, corn dogs and ready-to-eat (RTE) meals,
among others, remind us of how far we are from having a full
understanding of the ecology, transmission and control of L.
monocytogenes in foods and food processing environments.
A Well-Founded Scare
We all know that L. monocytogenes can be a challenging
pathogen to control. First, it is a common bacterium in natu-
ral environments, including vegetation, agricultural soils and
livestock, so it may be brought into the plant in raw animal
and plant materials, dust, water and even
through plant employees. Secondly, it typi-
cally finds its niche in cold, humid environ-
ments, making it a potential nightmare to
control in RTE meat processing facilities once
it has established itself on the premises. Its
ability to form biofilms and persist in this
protective microbial community is one of
the most common reasons for its difficult eradication, despite
aggressive cleaning and sanitizing. Lastly, L. monocytogenes can
survive and even grow in refrigerated, packaged RTE products,
including those packed under low-oxygen conditions.
Unlike produce handling and processing facilities, where
Listeria spp. is somewhat expected to be present from time
to time, companies that process RTE meats cannot afford to
have L. monocytogenes. Postlethality-treated product that comes
in touch with contaminated direct-contact surfaces or product
that is directly contaminated after a lethality treatment be-
comes adulterated as per the U.S. Department of Agriculture-
A look at control