Meat+Poultry - January 2022 - 54

FOOD SAFETY
from a sample, then they start looking for the
pathogenic bacteria. When USDA conducts
testing, the agency usually is looking for the
pathogenic Listeria strain itself.
ENVIRONMENTAL INSPECTION
Since Listeria does come from the
environment, it is commonly found in soil
and water, according to Season Yicheng Xie,
PhD, meat and poultry applications scientist at
Bio-Rad Laboratories, Food Science Division,
in Hercules, Calif. Research has indicated that
Listeria can also be found in the digestive
tracts of farm animals and their feces. It is
considered one of the " big three " foodborne
pathogens causing illness in people.
" Listeria monocytogenes is one of the
most prevalent bacterial pathogens that
cause foodborne illness and has the highest
death rate among other bacterial pathogens.
It usually is associated with ready-to-eat
products, including dairy products, processed
Listeria monocytogenes is
one of the most prevalent
bacterial pathogens that
causes foodborne illness.
meat, seafood and fruit, " Xie said.
" L. monocytogenes is also very different
from other foodborne pathogens. Compared to
the majority of bacterial foodborne pathogens
that are originated from the food itself, L.
monocytogenes is an environmental-borne
organism. And unlike other bacterial foodborne
pathogens that are just surviving or even dying
in refrigerated temperatures, L. monocytogenes
can grow in this condition, " she said.
There is no doubt that getting rid of this
pathogen has posed more of a challenge for
the meat and poultry industry. " Other bacterial
pathogens that are originated from food could
be eliminated during lethal steps that can be
taken (heat, irradiation, chemical treatments
etc.). But since L. monocytogenes is widely
spread in the environment, even with the
lethality step, L. monocytogenes could be
re-introduced to the finished product from the
plant processing environment, " Xie said.
The fact that refrigerated and frozen
ready-to-eat foods have a longer shelf
life and can be distributed more widely
allows the growth of pathogenic
Listeria during storage. She also
pointed out the difference between
Listeria species and Listeria
monocytogenes. Species refers to
diverse types of Listeria, including
those not harmful to people. Listeria
monocytogenes is the pathogenic type of
Listeria that is harmful to humans.
Xie also differentiated how testing is
done for Listeria. " Typically, environmental
samples are submitted for Listeria spp. and
finished (food) products are submitted for L.
monocytogenes, " Xie noted. She explained
that according to the Ready-to-Eat Meat and
Poultry Products guidelines, food producers
will submit environmental samples for Listeria
species as the indicating organism to ensure
the sanitation of the production environment
and ensure that there is little risk that L.
monocytogenes could be re-introduced to
the finished food products. " That would be
because the environment has been found free
of Listeria species.
" The food producers could also develop
a sampling program to evaluate the finished
product and make sure that L. monocytogenes
has been eliminated by the lethality step and
has not been re-introduced into the finished
products, " Xie offered as another alternative.
The Bio-Rad scientist also explained some
of the products the company has developed to
fight pathogenic Listeria in meat, poultry and
other food products.
They include " products for enrichment,
detection and confirmation of Listeria spp. and
L. monocytogenes, " Xie said. " There are several
ways to detect Listeria. Bio-Rad offers RAPID
chromogenic media and real-time PCR methods
for detection of these organisms. RAPID'L.mono
Agar is listed for use in many international
reference methods, including the FDA BAM,
Health Canada Compendium, and ISO standard.
iQ-Check real-time PCR kits are validated to
reduce the time to results overall. Both allow
for fast, accurate detection of both Listeria spp.
and L. monocytogenes, " she said.
Clear Labs, based in San Carlos, Calif.,
offers the Clear Safety Platform, a nextgeneration
sequencing-based technology
that allows the company and meat and
poultry processors to look at many parts of
the Listeria genome (the complete set of
instructions that would allow Listeria to
develop), if Listeria is present in a food or
environmental sample.
" So, with this technology, we can determine
if Listeria is present. Also, we can characterize
the detected organism, " described Kyle
Rhoden, director of product management
Bio-Rad
Meat+Poultry - January 2022

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