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Some seafood processors use antimicrobial agents on raw
RTE fish fillets before cold smoking to reduce pathogenic
bacteria, including L. monocytogenes. Although antimicrobial
agents can be highly effective (5-log reduction) to sanitize
clean food contact surfaces, seafood processors should not
rely solely on antimicrobial agents to eliminate or reduce
Listeria on raw RTE salmon fillets. Whereas there is limited
information in the scientific literature on the effectiveness of
antimicrobial agents in reducing Listeria on raw fish fillets,
three separate publications, one for acidified sodium chlorite
(ASC) and two for ozone on salmon fillets, all showed ≤1-log
reduction (5, 6, 17). Su and Morrissey (17) evaluated the use
of a wash of 50 ppm of ASC for 1 min on L. monocytogenes
inoculated salmon fillets and found only a 0.52-log reduction
of L. monocytogenes; the authors suggested that the reduced
efficacy of the ASC was probably due to reactions with
organic substances, such as fish proteins. Crapo et al. (5)
evaluated the efficacy of ozonated water at 0.6 to 1.5 ppm to
reduce Listeria innocua inoculated onto raw salmon fillets;
they concluded that, whereas ozone can reduce bacterial
levels in pure culture, it was not effective at reducing
L. innocua (<1-log reduction) on salmon filets. The authors
also suggested that organic material, such as proteins,
present on the surface of the fish fillets may react with the
ozone in the water, reducing its effectiveness. Crowe et al.
(6) evaluated the efficacy of ozone and found that the use
of three spray passes of 1 mg/L (1 ppm) aqueous ozone
generated a 1.17 ± 0.04-log reduction of Listeria inoculated
on salmon fillets. Su and Morrissey (17) and Crapo et
al. (5) emphasized the importance of preventing crosscontamination and of effective sanitation of food contact
surfaces as critical control measures for L. monocytogenes.
Effective control measures for L. monocytogenes are
especially important for smoked seafood processors.
Smoked seafood was ranked as the fifth highest food
category on a per serving basis for the risk of causing
listeriosis in the 2003 FDA, U.S. Department of
Agriculture risk assessment for L. monocytogenes (26).
The risk assessment utilized data from 24 international
and 6 domestic smoked seafood studies that showed that
13% of retail smoked seafood samples had detectable
levels of L. monocytogenes. A preliminary determination
of the risk assessment was a need for additional domestic
data on the prevalence of L. monocytogenes in the United
States. Concurrently, a 2003 publication by Gombas et
al. (9) on RTE foods determined the presence and levels
of L. monocytogenes in select retail foods from the United
States to estimate consumer exposure and support the
need for control strategies. This survey tested 31,705
food samples from retail firms in Maryland and California
collected weekly from 2000 to 2001. L. monocytogenes was
found in 114 (4.31%) of 2,644 smoked seafood samples.
Enumeration of L. monocytogenes from the 114 positive
samples showed that 78 samples had ≥1 CFU/g, 27

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ranged from >1 to 102 CFU/g, 7 ranged from >102 to 104
CFU/g, and 2 ranged from >105 to 106 CFU/g.
A 2008 report on FDA's strategy to combat listeriosis
indicated that the joint efforts of industry, government,
consumers, and academia led to a reduction in the incidence
of listeriosis in the United States from seven to three cases
per million people between 1986 and 2006 (12). This report
found that, from 1986 to 2006, fish was the most recalled
food for contamination with L. monocytogenes.
More recently, a 2017 publication of a survey for L. monocytogenes in RTE foods suggested that the efforts of industry
and regulators to control L. monocytogenes have contributed
to a significant decrease in contaminated smoked seafood
(13). This survey provided the results of 27,389 food
samples collected weekly from supermarkets in California,
Maryland, Connecticut, and Georgia from 2010 to 2013.
The survey found L. monocytogenes in 2 (0.27%) of 745
smoked seafood samples, which was significantly lower
than the 4.31% prevalence published in 2003 by Gombas
et al. (9). Enumeration of L. monocytogenes from the two
positive samples showed a range of 9 to 250 CFU/g, which
is less than the maximum concentration of 1.5 × 105 CFU/g
published by Gombas et al. (9). The authors suggested
that this decrease in L. monocytogenes contamination was
likely due to many factors, including industry practices and
regulatory policies.
In January 2017, FDA issued the revised draft guidance
for industry " Control of Listeria monocytogenes in Ready-toEat Foods. " However, FDA continues to detect L. monocytogenes in RTE food processing areas, leading to numerous compliance actions. This paper offers insight into FDA
inspections intended to identify controls and obtain data
on the prevalence of L. monocytogenes within cold-smoked
salmon facilities. Although these inspections were conducted
in 2011, many of the observed insanitary conditions are
similar to recent noncompliant inspections of seafood
facilities where FDA found L. monocytogenes in RTE food
processing areas. The findings and recommendations in
this manuscript are relevant to all RTE food processors,
especially seafood processors.
MATERIALS AND METHODS
FDA investigators conducted current good manufacturing
practice (CGMP) inspections and environmental sampling for
L. monocytogenes in 15 cold-smoked salmon facilities between
July and December 2011. The objectives of the inspections
were to identify current operating practices and controls and
to obtain data on the prevalence of L. monocytogenes.
CGMP inspections were conducted according to 21 CFR
Part 110 and focused on the potential for cross-contamination
of finished product from equipment, food contact surfaces,
food, and employees (25). Investigators discussed sanitation
procedures with management, reviewed their procedures if
written, and observed employees during cleaning and sanitiz-

Food Protection Trends - March/April 2021

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