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Listeria in Food Processing Facilities Study

In 2008, an outbreak of listeriosis caused by contaminated ready-to-eat (RTE) deli-meat resulted in 23 deaths and over 50 severely ill persons across Canada.  The meat was produced in a federally registered and inspected facility in Ontario.  Are RTE foods produced in BC under provincial inspection authority contaminated with Listeria monocytogenes, the bacteria that causes listeriosis?  To answer this question, a survey was conducted in 2009 in dairy, fish and meat facilities in BC that produce RTE foods.  The survey was conducted to estimate the prevalence of generic Listeria and Listeria monocytogenes in the foods and production environments of BC food processing facilities.

Methods:

Dairy, meat and fish facilities were visited by inspectors (Environmental Health Officers and Food Safety Specialists) between August and October 2009.  At each facility, up to 6 food and 6 environmental swab (sponge) samples were taken (sampling method).  The food samples were tested in the PHSA Laboratory using an approved method (MFHPB-30 and MFLP-74 summary)  to culture and enumerate Listeria found in foods.  Swabs were taken from three areas in each facilitiy:  food contact surfaces, close-to-food contact surfaces and non-food contact surfaces.  Swabs were also tested for Listeria.  Swab samples are useful to find out if Listeria is present on surfaces such as slicers and work tables where food is prepared. 

Results:

A total of 262 RTE food and 305 environmental swab samples were tested in the 53 facilities visited (17 dairy, 13 fish and 23 meat).  Overall, generic Listeria species (generic Listeria include Listeria monocytogenes and other Listeria bacteria which grow in the same environmental conditions but do not themselves cause disease in humans)  were found in 9% and Listeria monocytogenes was found in 5% of ready-to-eat foods. When considering results by type of facility, Listeria monocytogenes was only found in ready-to-eat foods collected from fish processors (chart, right).     The types of foods contaminated included cold-smoked salmon and hot-smoked salmon products such as salmon leather and jerky (complete list of foods).

Generic Listeria species were recovered from 30% of non-food contact surface swabs, 5% of close-to-food contact swabs and 6% of food contact swabs. When comparing the proportion of facilities with environmental surfaces positive for Listeria and Listeria monocytogenes (note: only facilities that met the criterion of at least one swab sample collected in the three sampling areas were included), higher rates of Listeria and Listeria monocytogenes were found in fish facilities in comparison to meat and dairy facilities (chart, right)  .  

Further, Listeria monocytogenes was only found on food contact surfaces in fish processing facilities. 
This chart shows that although generic Listeria was found on non-food-contact surfaces in all types of processing facilties (dairy, fish and meat), only in fish facilities was Listeria monocytogenes found on food-contact surfaces and on foods. This points to a lack of hygienic control in fish processing facilities.  Put another way,  this chart also shows that where ready-to-eat foods were positive for Listeria monocytogenes, generic Listeria was also found in the environment - this demonstrates the value of monitoring for LIsteria using environmental swabs in processing environments.

What this study tells us and what the public needs to know:

 It is clear from this study that fish processing facilities producing ready-to-eat foods require special attention.  Public health and government agencies will continue to work together at all levels to ensure risks from ready-to-eat foods are controlled. 

The public is reminded that for “vulnerable populations” – especially pregnant women and the elderly – there is a risk of becoming ill when consuming certain kinds of foods such as deli-meat, soft cheese and smoked fish.

 
For a list of recommendations from this study please see the executive summary and the full report

Last Updated: April 3, 2014