July/August 2019 - 30

UNITED FRESH WWW.UNITEDFRESH.ORG
Join the fight against Listeria monocytogenes
L i s te r ia
monocy t ogene s
is
r ec o g n iz ed
a
By Ben Massoud
Manager of
Communications,
United Fresh
Produce
Association
i nc r ea s i ng l y
a s
pa t hogen of
concern in fresh
produce handling
and
Listeriosis
Listeriosis is a serious infection usually
proce s s i ng
operations.
A Gram-positive,
rod-shaped, nons
pore formi ng ,
motile bacterium,
L. monocytogenes
is capable of persisting under varying
environmental conditions. Its ability
to establish residence in hard-to-clean
places makes it more difficult to kill
with routine cleaning and sanitizing
procedures. In fact, it can survive in
facilities and equipment for many years.
Unlike other human pathogens,
listeria is capable of growing at
temperatures below 40°F, with a
growth range of 32°-113°F. Listeria is a
" facultative anaerobe, " meaning it does
caused by eating food contaminated
with L. monocytogenes. Outbreaks of
listeriosis associated with fresh produce
are generally traced to produce handling
and processing environments, not the
growing environment.
Relative to other pathogens, L.
monocytogenes causes comparatively
few illnesses, but it is among the leading
causes of death from foodborne illnesses;
about 15-30% of listeriosis cases result
in death (US FDA, 2012). According
to the Centers for Disease Control &
Prevention, an estimated 1,600 people
get listeriosis each year and about 260
die. The infection is most likely to sicken
pregnant women and their newborns,
adults aged 65 or older and people with
weakened immune systems.
not require oxygen to survive and grow,
and can grow in modified atmosphere
packaged products, particularly those
with extended shelf life.
FDA considers L. monocytogenes on
any ready-to-eat (RTE) food, including
most fresh produce, an adulterant, and
the food subject to recall. Listeriosis
outbreaks have been linked to produce
including cabbage, fresh-cut celery,
bagged salads, whole cantaloupes,
caramel apples and others.
Monitoring Listeria monocytogenes
L. monocytogenes is generally
considered a soil bacterium and can
be found in soil samples more commonly
than salmonella and pathogenic E.
coli (Chapin et al., 2014), dependent
on the region. As a result, facilities
are constantly challenged to keep the
pathogen from establishing itself in
a facility, entering with people, raw
materials, or equipment. If intruding
L. monocytogenes is not removed
during the sanitation process, it can
find a niche in harvesting equipment,
processing and packaging equipment,
facility structures, drains, floors,
cooling units, transportation equipment,
forklifts, produce harvest and handling
containers, pallets or other places where
it may transfer to product.
The potential for contamination
and entrenchment in equipment
heightens the need for those who
perform packing and/or processing to
have strong environmental monitoring
and sanitation control programs.
Additionally, the FDA recommends
establishing and using a preventive
maintenance program that is designed
to minimize breakdowns and prevent
contamination that could occur
during repair of equipment sanitation
monitoring. Verifying sanitation
conditions and practices by actively
looking for listeria species in the
production environment should be done
with sufficient frequency to demonstrate
that the facility and equipment is not
harboring the organism.
A well-designed environmental
monitoring program is a more effective
program than product testing alone,
and it 's
recommended that
the
environmental monitoring procedures
use a risk-based approach in which
30 JULY/AUGUS T 2 019
http://WWW.UNITEDFRESH.ORG
July/August 2019

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