Annex III - CONTROL GUIDELINES
To effectively manage the risk of product contamination it is
necessary to assess where along the product flow the exposed food
is more likely to become contaminated. This is generally wherever
something has direct contact with the unpackaged product.
Examples of some primary sites leading to product contamination
- Brining solutions and injection equipment;
- Slicing equipment;
- Packaging equipment;
- Water or ice used in processing/storage;
- Racks for transporting finished product;
- Hand tools, gloves, aprons, etc. that contact exposed
- Spiral freezers/blast freezers;
- Containers such as bins, tubs, or baskets used for
holding a food while it is waiting to be further
processed or packaged.
Other areas of the environment can also serve as secondary
sources of L. monocytogenes. These areas may harbour
the organism and under certain conditions lead to contamination
of the above product contact surfaces or the food. By controlling
the presence of L. monocytogenes in the environment
it is possible to reduce the risk that product or a product
contact surface will become contaminated. The significance of
these areas will vary depending upon the facility, the process(es),
the temperature and humidity of the room, and the food. Examples
of such secondary sources include:
- Equipment framework and other equipment in the area;
- Walls, especially if there are cracks that retain
- Ceilings, overhead structures, catwalks;
- Insulation in walls or around pipes and cooling units
that has become wet;
- Trolleys, forklifts, walk-alongs;
- Cleaning tools such as sponges, brushes, floor scrubbers;
- Maintenance tools.
Consideration should also be given to the potential for L. monocytogenes
to be brought back into the clean environment. This may be the
result of traffic in the processing and packaging areas (people
and equipment, such as trolleys and forklifts, that enter from
more contaminated points in the operation) or unscheduled
It should be recognized that in a plant with an effective
control programme L. monocytogenes contamination,
when it occurs, is line or equipment specific. While it is
possible to have random isolated contamination with L. monocytogenes
in a controlled environment, contamination more likely will occur
after the organism has become established in a niche. When this
happens, routine cleaning and sanitizing become less effective in
controlling the organism. As the equipment is operated, the
bacteria work their way out of the niche and become deposited
onto the outer surfaces of the equipment. As product moves over
or through the equipment, the contamination is spread downstream
to other areas along the product flow. This situation can be
corrected only by identifying the source or niche of L. monocytogenes
growth and eliminating it. Among the sites found to be
potential harbourages are the following:
- Hollow rollers for conveyors;
- On/off switches;
- Rubber seals around doors;
- Damp insulation;
- Conveyor scrapers, especially if frayed and in poor
- Open bearings within equipment;
- Hollow implements, including box cutters;
- Trash cans and other such ancillary items;
- Standing water in production areas;
- Cleaning tools, including mops and sponges;
- Poorly maintained in-line air filters through which
compressed air must pass;
- Wet rusting or hollow framework;
- Motor housings;
- Walls/crevices of spiral freezers;
- Ice makers.
- Condensate traps in vacuum pumps
In addition to the possible establishment of L. monocytogenes
in a niche, consideration must be given to certain conditions or
situations that present an extra risk for contamination of
finished products with Listeria contamination. When such
events occur, processors may need to take extra precautions to
guard against contamination. Examples of such situations include:
- Moving or significantly modifying a packaging line.
- Installing used equipment or equipment that has been in
storage or used in another plant.
- Equipment breakdowns.
- Construction or major modifications in the product
handling and packaging area (e.g., replacing
refrigeration units or floors, replacing or building
walls, modifications to sewer lines).
- Using employees that are not familiar with the operation,
the L. monocytogenes control procedures in
use, or the procedures for cleaning equipment in the
production area where ready-to-eat (RTE) foods may be
exposed to contamination.
- Personnel who handle RTE product contact surfaces or
equipment that are likely to be contaminated (e.g.,
floor, trash cans) and not changing gloves or following
other required procedures before handling product.
- Difficulty in meeting scheduled cleaning of the floors of
holding coolers due to heavy production schedules.
- A drain backing up.
- Product being caught or hung-up on equipment. Stagnant
product in a system can be a major site of microbial
growth during production. The equipment should be
modified to eliminate areas where product stops moving
along or through a processing line.
- Raw or under-processed product being detected in a cooked
product area. If this occurs, the process must be
stopped, the unacceptable product removed, and the
equipment re-cleaned and sanitized.
- Frequent changing of packaging film, labels, line speeds,
etc. due to frequent changes of product being packaged.
- Personnel being used interchangeably for packaging raw
and cooked products.
- Increased production requiring wet cleaning of down lines
in the same room as lines running product.
- Cleaning of equipment parts, tubs, screens, etc. on the
- Waste bins in the ready-to-eat area not being properly
maintained, cleaned and sanitized. Personnel handling
product may come into contact with these items and then
contaminate product and/or product contact surfaces.
Specific Considerations: Processing Area
As noted before, certain types of raw fishery products as well
as other ingredients used in processing may contain L. monocytogenes,
although the presence of the organism and the levels of
contamination vary widely. Because of this potential, steps
should be taken to minimize the potential for cross-contamination
from raw ingredients to products that have been treated to
eliminate or reduce the contamination.
Separating raw products from semi-finished and finished
products is a key factor in preventing cross-contamination.
- Wherever possible, there should be linear flow of product
through the operation from the raw ingredients to the
- Plants should be rearranged, where necessary, to
improve the flow of product, equipment, and
people to facilitate separation of raw from
cooked or treated product.
- It is desirable to establish positive airflow on
the "clean" side of the operation
relative to the "dirty" side (e.g.,
maintain negative air pressures in raw product
areas and positive pressures on the clean or
finished product side).
- Compartmentalize operations as needed to enhance the
separation of raw ingredients and processed products.
- Provide separate, dedicated washing areas and clean-in-place
systems for cooked or treated product equipment and
raw processing equipment.
- Rework and trash barrels for cooked or treated
product areas should be labelled or colour coded and
not used elsewhere in the plant. They must be cleaned
and sanitized daily or more frequently if
microbiological testing data indicate this is
- Remove hoses from the manufacturing areas where ready-to-eat
products are exposed before start of operation each
day so that line workers are not tempted to use these
for spot cleaning during production.
- Consider having separate utensils, carts, racks,
totes, equipment, cleaning utensils, etc., colour
coded where practical, for the ready-to-eat product
- Where possible, eliminate overhead fixtures in the
- Where possible, isolate wet process areas from other
production areas; at a minimum, remove standing water
as soon as possible.
- Control traffic flow patterns between the raw ingredients
and the processed products sides of the operation to
prevent transfer of L. monocytogenes from
the "dirty" or "raw" side of the
operation to the "clean" or "cooked"
- Equipment, utensils and people in raw and cooked
areas should not be interchanged during the
- Drains from the "dirty" or "raw"
side should not be connected to those in the
"clean" or "cooked" side.
- If footbaths are installed, they must be properly
maintained, or they can become a source of
contamination. Maintaining clean dry floors is
preferred to the use of footbaths, unless there
is a specific need that cannot be addressed
otherwise. Footbaths should contain stronger
concentrations of sanitizer than would normally
be used on equipment (e.g., 200 ppm iodophor, 400-800
ppm quaternary ammonium compound); a depth of 2
inches is recommended. Chlorine is not
recommended for this use as it becomes too
quickly inactivated. If chlorine is used, strict
attention must be given to maintaining its
strength. Footbaths will be ineffective if
cleaved boots are carrying large particles of
- Another option is to spray a foam disinfectant on
the floor as people or rolling stock (carts,
forklifts, etc.) enter the room.
Water used in processing operations that will come in contact
with product should contain an antimicrobial known to be
effective against L. monocytogenes and approved for
the specific application at the levels used.
Specific Considerations: Packaging and Storage
Pallets entering the packaging room must be clean, dry and in
good condition and preferably not made of wood.
Store and package exposed products in a clean, dry environment.
- Bacteria cannot multiply without water. If the
environment is clean and dry, L. monocytogenes
remains dormant or, perhaps, dies.
- There is less transfer of bacteria from surfaces if the
surfaces are clean and dry.
- The spread of contamination by vehicular and pedestrian
traffic is reduced considerably if the floors are clean
- The cooling units in packaging rooms and coolers for
exposed product should have dehumidifying capability. To
facilitate the removal of humid air and to dry floors
after cleaning, it may be necessary to exhaust air
outside the plant. Heating air within a room can also be
effective for removing moisture at the end of the
Specific Considerations: Equipment
Equipment should be properly designed and maintained.
- Equipment must be designed to facilitate cleaning and to
minimize sites where microbial multiplication can occur.
The acceptability of the design of new or replacement
equipment should be reviewed to determine its
cleanability and its potential to minimize microbial
- Even though visually clean, previously used equipment may
harbour pathogens. Plan accordingly, prior to putting
such equipment into production.
- Properly maintain equipment to minimize breakdowns and
the risk of contamination during repair.
- Equipment that is damaged, pitted, corroded, or cracked
should be repaired or replaced.
- Equipment or catwalk framework should not be hollow such
that water can collect and harbour L. monocytogenes.
- Lubricants can become contaminated with product residue
and become a centre for growth of L. monocytogenes.
Use lubricants that contain listericidal additives (e.g.,
- Avoid conveyor designs and locations that are difficult
to clean and sanitize. Conveyors for product prior to
packaging should not contain hollow rollers. Do not
locate conveyors or other processing equipment in which
product is exposed near the floor, as this is a likely
source of L. monocytogenes. Avoid overhead
conveyors, if possible, as they are more difficult to
clean, sanitize and inspect. Either provide a safety
ladder or design the conveyor so it can be lowered for
- Racks used for transporting exposed cooked product should
have cover guards over the wheels to prevent spray from
the wheels falling onto the rack and product as the racks
- Racks used in operations after products are cooked can be
a significant source of contamination if not properly
cleaned and sanitized before use. The most reliable
method of sanitizing racks is with heat. Heat can be
applied by (1) a hot water (82.2° C/180° F) rinse in a
rack washer so the racks will reach a temperature of 71.1°
C/160° F or higher, (2) steam applied in a cabinet after
cleaning in a rack washer, or (3) placing the racks into
an oven and applying moist heat to raise the temperature
of the racks to 71.1° C/160° F or higher. When using
heat to sanitize, it is essential that the equipment be
thoroughly cleaned so the heat does not bake the soil on,
making it more difficult to remove, resulting in more
contamination problems in the future.
- Regular maintenance schedules should be adopted and
followed to minimize the potential for harbourages and to
reduce the potential for contamination of equipment due
to unscheduled repair operations.
- For maintenance of equipment in the cooked, RTE area it
may be necessary to use tools dedicated to this area or
to sanitize tools prior to use in this area. Maintenance
personnel should wear clean smocks that are not used in
raw material areas. Equipment should be re-sanitized
after maintenance work.
Specific considerations: Plant Sanitation
- Use sanitation procedures designed to control L. monocytogenes.
The frequency of cleaning and sanitizing the equipment
and environment of a plant depends upon experience and
microbiological data. Routine microbiological testing
allows the plant to develop a baseline for comparison
purposes, observe trends, and detect a developing
- Successful control of L. monocytogenes
requires consistency and attention to detail. The steps
include (1) dry clean, (2) pre-rinse the equipment, (3)
visually inspect the equipment, (4) foam and scrub the
equipment, (5) rinse the equipment, (6) visually inspect
the equipment, (7) clean the floors, (8) sanitize the
equipment and floors, (9) conduct post-sanitation
verification, (10) dry the floors, (11) clean and put
away supplies. Some equipment may require disassembling
prior to cleaning and sanitizing, and may need to be re-sanitized
- Quaternary ammonium compounds (quats) have been found to
be effective against L. monocytogenes, and
leave a residual germicidal effect on surfaces. In
addition, sanitizers containing peracetic acid and
peroctanoic acid have been shown to be effective against
biofilm containing L. monocytogenes. Areas
that should be sanitized with such compounds and a
suggested frequency are as follows:
|Waste containers & storage
|Condensate drip pans
|Heating ventilating air conditioning (HVAC)
- The cleanup crew should receive special training in
proper procedures to control L. monocytogenes.
Close monitoring and correction is essential to improve
and maintain a high level of performance.
- Priority must be given to rooms and equipment used for
holding and packaging exposed ready-to-eat product.
Consideration should be given to assigning reliable
personnel to areas where ready-to-eat products are
handled and packaged.
- It is very desirable, even necessary in some cases, to
have a person on the staff whose primary responsibility
is to monitor the cleaning and sanitizing process at
night to be certain it is being done correctly. Concerns
over having the plant ready on time for start-up must be
secondary to having the plant correctly cleaned and
sanitized. Extensive experience indicates that, if the
equipment is properly cleaned and sanitized before start-up,
the risk of contamination from equipment during
production is minimal.
- The utility of mid-shift cleanups is not entirely clear.
In certain situations, they may be counter-productive by
increasing the risk of L. monocytogenes contamination.
There may be instances however when this is necessary to
reduce contamination. Microbiological testing should be
conducted to determine the utility of this practice in
- Some plants have found the following sanitizing procedure
to be helpful each night. After cleaning the equipment,
apply a high level of sanitizer (e.g., 800 ppm quat),
allow it to stand for about 20 minutes, rinse thoroughly,
and then apply the normal level of sanitizer (e.g., 200
ppm quat or chlorine). At the end of the production week
the high level of sanitizer can be left on the equipment
until before start-up. The sanitizer is then rinsed, the
normal level is applied, and the room is prepared for
start-up. Under certain circumstances, it may be
beneficial to spray an aerosol of 200 ppm quat into a
room as a final step in the process of cleaning and
sanitizing; weekly or monthly fogging may be useful.
- Rotating other sanitizers (e.g., chlorine, acid-anionic,
peracid and iodophors) into the sanitation programme may
provide for greater effectiveness. Consider using new
peracid-based sanitizers such as Matrixx, Vortexx and
others where they have been demonstrated to be effective
against L. monocytogenes.
- Modify equipment so it is simple in design, easy to
clean, and has fewer maintenance problems. Breakdowns
during production increase the risk of L. monocytogenes
- Sanitizing with high temperatures, if manufacturers
instructions permit such application, may be particularly
useful for biofilm removal.
- Hot water/steam sanitation is an alternative to chemical
sanitation that is especially effective where equipment
is difficult to clean. Wherever possible, apply steam as
a final step for equipment that is difficult to clean.
One method is to place a metal cover over the equipment
and then inject steam. In some cases, equipment can be
steamed in a cook oven. The objective is to heat the
equipment so it will reach at least 71.1° C/160° F
throughout. A holding period of one hour or more is
desirable. For equipment that may be more sensitive to
heating it may be necessary to use a lower temperature (e.g.,
62.8° C/145° F) and a longer holding time. (See earlier
cautions about thorough cleaning prior to application of
- Plastic tubs which can be stacked may be a problem unless
they are cleaned and sanitized daily. They must not be
placed directly on the floor, unless placed on a clean
- Infrequent cleaning of coolers used for holding finished
unpackaged product is a common cause for increased L. monocytogenes
problems, particularly during peak periods. These coolers
should be emptied and cleaned at least once per week.
Maintaining dry floors in these coolers is also important.
- Infrequent defrosting, cleaning, and maintenance of
spiral freezers used for freezing unpackaged product is a
potential source of L. monocytogenes. These
freezers should be cleaned twice a year.
- Condensate that accumulates in drip pans of refrigeration
units should be directed to a drain via a hose. Care must
be taken to ensure that the hose does not become blocked.
Solid forms of sanitizers (e.g., blocks or donuts of
quats) can be placed in the drip pan to control microbial
growth. In addition to the routine use of sanitizers,
drip pans should be cleaned regularly.
- Using compressed air to remove debris from equipment
during production can increase the risk of contamination.
Compressed air can be a source of L. monocytogenes
when in-line filters are not maintained or replaced with
regularity. Thus, when compressed air must be used
directly on product or product contact surfaces, the air
should be filtered at the point of use and the filters
maintained. This practice should be restricted,
preferably, to cleaning certain equipment (e.g.,
packaging machines) at the end of production before
- Never clean coolers or other rooms when exposed, ready-to-eat
product is present. Do not rely on covering the product
with plastic or paper. Remove all unpackaged product from
the room before beginning to clean.
- Do not dismantle and wash equipment on the floor.
- The best method for cleaning floors is to use a powdered
caustic cleaner, apply water as needed, use a dedicated,
colour-coded brush to clean the floor, and then
thoroughly rinse, using a low volume hose, and sanitize
the floor. Newer cleaners and sanitizers may be more
effective for controlling L. monocytogenes on
the floor. Floor scrubbers can be helpful, particularly
for cleaning large open spaces such as hallways. The
equipment used for cleaning must be maintained and
properly cleaned so it does not become a source of
contamination. Application of powdered citric acid to
certain areas of the floor may be effective for
controlling L. monocytogenes, provided the
floor has been properly cleaned and dried before applying
the citric acid. For maximum effectiveness, the surface
of the floor should be maintained at pH 5.0 or below.
Litmus paper can be used to check the pH. While this may
help control L. monocytogenes, the condition
of the floor should be monitored, as the acid condition
will cause deterioration that eventually will necessitate
replacing the floor.
- Floor drains must be designed and maintained to prevent
backups. If a backup occurs, production must cease, the
drain cleared, and the area carefully cleaned with
caustic, rinsed, and sanitized. Avoid splashing equipment
during the process. The floor should then be dried. Never
use a high-pressure hose to clear a drain. An aerosol
will be created that will spread contamination throughout
- Whenever possible, eliminate trench drains.
- Bactericidal drain rings are recommended.
- Floor drains should be cleaned and sanitized in a manner
that prevents contamination of other surfaces in the room.
Floor drain brushes must be at least 5 mm (¼ inch)
smaller than the diameter of the drain opening or a
splashguard must be used to prevent splashing during
cleaning. Utensils for cleaning drains should be
dedicated to that purpose to minimize the potential for
contamination. If floor drains are cleaned first, it may
be necessary to clean and sanitize them again at the end
of the process.
- Cleaning tools should be sanitized using 600-1000 ppm
quat solutions and either stored dry or in quat solutions
maintained at 1000 ppm.
Specific Considerations: Personnel Hygiene
Establish personal hygiene practices with L. monocytogenes
control as a major objective. The following information should
become part of employee training for L. monocytogenes
- Clean gloves, smocks, and aprons are essential to protect
against product contamination. Ideally there should be
one colour smock for the raw side of the operation and
one for the processed side. Disposable gloves and aprons
should be used wherever possible in cooked product areas.
Disposable paper sleeves (arm covers) can provide another
barrier for those who handle exposed product. Disposable
items should be discarded when leaving the work area and
replaced with new when returning. Some garments (e.g.,
smocks) may be left in the department and re-used,
provided they are still clean. Gloves should be replaced
if damaged. The use of gloves does not preclude the need
for employees to wash hands regularly.
- Everyone working in areas where ready-to-eat products are
exposed must clearly understand that the purpose of
wearing clean garments and disposable gloves is to
protect the product from contamination, not protect
themselves from getting dirty.
- If an unclean surface is touched, then hands should be
washed and gloves changed.
- Equipment and soiled clothing must not be stored in
- If possible, assign a person in the packaging room to
pick up material from the floor, remove trash, and
perform other housekeeping tasks. This person must not
work on a packaging line or handle product that will be
packaged or replaced on the line.
- Rubber boots that are non-porous and easily cleaned are
better for L. monocytogenes control than
other footwear. Boots are necessary where footbaths are
ENVIRONMENTAL MONITORING PROGRAMME TO VERIFY CONTROL
An environmental monitoring programme is recommended to assess
the need for additional control measures for products that may be
recontaminated by L. monocytogenes. Industry
experience has shown that an ongoing monitoring and control
programme that uses Listeria species (Listeria spp.
or "generic Listeria") as an indicator of
potential L. monocytogenes contamination not only
reduces the possibility of finding L. monocytogenes in
finished product but other pathogens as well. Industry experience
also shows that re-entry of Listeria spp. into the
production environment cannot be reliably prevented. Thus,
ongoing monitoring to detect the organism in the environment is
Each company should establish its own L. monocytogenes
monitoring programme considering the guidelines outlined below.
General Principles for Verification of Environmental
Environmental monitoring (microbiological testing) should
focus on a non-pathogenic indicator such as Listeria spp.
or Listeria-like organisms, since these indicators will be
found more frequently in the environment than L. monocytogenes
and because test results are available sooner. Monitoring results
should alert the plant to potential problem areas, prompting
further investigation and focusing of additional control efforts,
as necessary. Goals for reduction of positives should be
established in order to encourage continuous improvement. A
detailed set of action plans should be developed to control the
risk of L. monocytogenes in the event that the goals
are not met.
Each plant, product, and process must be evaluated to
determine the appropriate monitoring points. Each packaging line
should be regarded as an independent unit for L. monocytogenes
monitoring and control. It is recommended that both food contact
surfaces and non-food contact surfaces that pose the potential to
contaminate product be tested. One approach might be to separate
testing into environmental sites, product contact sites, and
product itself. Keep in mind that since L. monocytogenes
will not be frequently found in products in operations following
these control guidelines and because it will not be uniformly
distributed, product testing will not be a reliable indicator
that L. monocytogenes contamination has not occurred.
Thus, the emphasis of the programme discussed here is on testing
for Listeria-like organisms in the environment to verify
control. There can be many variations on how this is done. Some
guidelines are presented below.
- Plants should determine the points to sample and the
frequency of sampling based on knowledge of their
specific operation and the controls that have been put
into place, as well as any microbiological data available.
Suggested areas include support structures, overhead
areas or structures, walls, floors, drains, and room air.
Weekly sampling is recommended initially for most wet
areas where L. monocytogenes can grow;
in dry-cleaned areas sampling may be less frequent.
- The number of sampling points and the frequency of
sampling may be adjusted based on results over time. For
example, repeated negative findings may suggest
elimination of a sampling site or a reduced frequency of
sampling for a particular area.
- Statistical Process Control (SPC) may be used to track
results and identify the need to take action.
- Plants should determine the action to be taken in the
event that Listeria spp. is detected at
frequencies exceeding the upper control limit, target, or
"trigger" that the plant has set (although some
attention should be given to cleaning and sanitizing an
area when any positive is found). Because the reasons for
a positive finding are likely to be plant-specific,
corrective actions will vary. Consider the following
points in determining corrective actions for
- Detection of Listeria spp. in an
environmental monitoring sample does not
necessarily indicate a microbiological control
problem; it does indicate that additional
investigation should be undertaken.
- When environmental monitoring results indicate a
trend toward an increased incidence of Listeria
spp., plants should investigate to determine the
reason(s) for the increase and should take action
to reduce the level again.
- If a positive sample is detected, and the sample
was a composite sample, the individual samples
should be tested to pinpoint the location of the
- Additional samples should be taken from the
environmental area where the positive was
detected. These samples may indicate that
additional corrective actions are needed in this
- If, after corrective actions have been applied,
additional samples are positive, the environment
should be intensively cleaned and re-tested.
- Consider the need to sample (additional) food
contact surfaces in the areas where environmental
positives are detected.
Food Contact Surface Testing
- Food contact surfaces may be sampled routinely for Listeria-like
organisms as verification that environmental controls are
preventing L. monocytogenes contamination of
surfaces; or they may be sampled only when environmental
monitoring suggests there may be a problem.
- As with environmental sampling, plants should determine
the points to sample, the time of day for sampling, and
the frequency of sampling based on knowledge of their
specific operation and the controls that have been put
into place, as well as any microbiological data available.
- Plants should investigate to determine the reason(s) for
all positives on food contact surfaces. Investigative
sampling must be capable of identifying equipment that
contains niches where L. monocytogenes has
become established. Until these sites are located, it is
not always possible to correct an ongoing problem.
- Corrective actions should be taken for all food contact
surface positives based on a pre-determined plan of
action and the actions should be documented.
Contamination of some product contact surfaces is of
greater concern than others. Examples of corrective
action include modifying cleaning and sanitizing
procedures, re-design of equipment, improved GHPs, etc.
- Plants should consider whether finding Listeria-like
organisms on food contact surfaces should result in the
need for product testing.
- Plants may decide to test product as a result of positive
food contact surfaces.
- In addition, random product testing may be used to verify
that the L. monocytogenes control/monitoring
programme is effective in preventing product
contamination. All sampled lots should be held until the
laboratory results are available.
- Plants must determine the action to be taken in the event
that L. monocytogenes is detected in a
Environmental Sampling Guidelines
- When taking swab or sponge samples, use a scientifically
- Samples may be composited where scientifically
appropriate; where possible, the remaining portion of
individual samples should be retained until composite
results are obtained, in case additional testing of the
individual samples is necessary.
- Packaging line samples (product contact surfaces) should
be from areas as large as practical. Environmental
samples should represent a constant area (e.g., 45cm x 45cm
(1.5 ft x 1.5 ft.), 61 cm x 91 cm (2 ft. x 3 ft.),
- Floor drains represent an almost constant problem area; a
corporate decision should be made on whether or not to
include drains in the environmental sampling program. A
separate goal for drains may be appropriate.
When an effective control programme for L. monocytogenes
is in place, the primary source of contamination is often a niche
where L. monocytogenes has become established and is
multiplying. When L. monocytogenes finds a niche, the
contamination will be line-specific. In general, the
contamination will flow downstream along a packaging line. When
seeking the source of a niche, collect and analyze sponge samples
individually, not as composites. Sample additional sites along
the line and sample more frequently throughout the day. Tear down
suspected pieces of equipment, collecting samples of suspicious
sites and materials. Clean and sanitize the equipment as it is
being reassembled. If cleaning and sanitizing are unsuccessful,
remove sensitive electronics, oil and grease and apply heat to 71.1°
C/160° F. Small parts can be placed in an oven; larger equipment
can be shrouded and steam applied under the tarp. Lower
temperatures for longer times may also be effective. Also
consider the possibility that employee practices may be involved
in the contamination. Refresher training in the controls
necessary to prevent L. monocytogenes contamination
may be indicated.