Listeria monocytogenes is the bacterium which causes listeriosis. Although relatively rare, listeriosis can be very serious for vulnerable groups – a recent outbreak in a health care setting has already claimed five lives in England this year (June 2019. L. monocytogenes is a hazard that must be considered and controlled in any healthcare/social care organisation that provides food for vulnerable groups.
Key areas for reducing the risk from Listeria in foods are:
- Preventing foods from becoming contaminated with L. monocytogenes
- Controlling and limiting the opportunities for growth of L. monocytogenes, through strict controls (appropriate shelf life and effective cold chain management)
- Thorough cooking of food to kill L. monocytogenes
Listeria monocytogenes is a bacterium of concern because it is widespread in the environment and can be found in vegetation, raw foods, soil, water and animal faeces.
L. monocytogenes can live in food processing environments. L. monocytogenes bacteria are able to attach to surfaces and adhere together within a slime-like substance to form biofilms, which are not usually visible. Once biofilms are established they are difficult to remove and can be resistant to cleaning and disinfection. During preparation food that comes into contact with a biofilm can become contaminated.
Unlike most other pathogenic bacteria, L. monocytogenes has the potential to grow, albeit slowly, at low temperatures, which includes refrigerator temperatures. It can even survive freezing and is salt tolerant. L. monocytogenes also has the ability to grow in low oxygen environments.
This means that the types of food that are associated with listeriosis outbreaks are:
Smoked fish • Cooked shellfish • Pate Meat • Cooked meats/ poultry • Cured meats Pasteurised/ unpasteurised cheeses • Soft blue veined cheeses • Mould-ripened soft cheeses • Pre-packed sandwiches • Prepared salads • Some cut fruits, including melon
Food provided by the main kitchen or central production kitchen to wards, dining rooms, day units and packed lunches; Food brought in by patients/ residents and visitors; On-site Vending machines restaurants, fast food outlets, coffee shops and on-site retailers, including volunteers are all ways that potentially contaminated food may find its way into your health care setting.
The effective management of cross-contamination is an essential food safety control for L. monocytogenes.
- identify the key sources of L. monocytogenes contamination which are: • Dirt and soil including dirty premises, equipment and cleaning equipment • Food handlers • Raw foods • Food preparation equipment and utensils • Water • Condensate from air cooling units • Drains and drainage gulleys • Areas prone to pooling water (such as the bottom of refrigerator units and blast chillers)
- Implement a personal hygiene policy to ensure staff follow effective personal hygiene practices
- Apply strict cleaning and disinfection regimes. Where possible disinfect food contact equipment by heat or by an adequate dishwasher cycle, following the manufacturer’s instructions . Use separate cleaning equipment for raw and RTE preparation areas to limit spread of contamination
- Wash fruit before use. Wash external surfaces before cutting fruits to minimise the risk of L. monocytogenes on the external surface from being transferred to the flesh of the fruit, for example, melon
- Control growth by maintaining the cold chain at 5°C or less. It is good practice for healthcare/social care organisations to:
– maintain their cold chain of chilled RTE food at 5°C or below from delivery through to service
– Use chilled display cabinets where RTE foods, requiring chill control, are presented for sale at retail in restaurants, shops, cafes etc
– Pre-chill equipment used for keeping foods cold, such as display cabinets, chilled trolleys etc
– Minimise holding times that chilled RTE foods are kept at ambient – Set maximum times that food can spend out of the cold chain, as part of the HACCP based FSMS and monitor this to check times are not exceeded – Make sure that chilled RTE foods are not stored next to or on top of ward trolleys, designed to keep foods hot
- Implement Shelf life controls
– Order/purchase as close to the date of consumption as practicable. Take care not to over order foods.
– Carefully check use-by dates upon delivery/purchase
– Organise working practices so that chilled RTE food prepared on site is used on day of production wherever possible. A maximum chilled shelf life of day of production plus 2 days should be applied, unless evidence of shelf life studies is provided to prove otherwise
– Bought in pre-packed sandwiches, whether provided by the organisation or by visitor/ patient, should be consumed as soon as possible
– Ensure stock is rotated, for example, using a ‘first in, first out’ principle
- Ensure time/temperature control during food preparation • Prepare food in small batches • Pre-chill ingredients such as canned tuna, mayonnaise and bread • Pre-chill crockery, for example chill plates prior to plating salads/sandwiches • Provide sufficient refrigerators close to preparation areas so that foods can be removed, used and put back promptly • Cold holding wells provided close to preparation areas will enable fillings to remain chilled during preparation • Only remove from refrigeration the amount of ingredients for foods such as salads and sandwiches, being prepared at that time • Refrigerate chilled RTE foods immediately following preparation
- Ensure time/temperature control during distribution to service points • Maintain the cold chain at 5°C or below • Where possible containers and equipment used for transportation of food should be pre-chilled to below 5°C • Remove chilled RTE food from refrigerated storage and place into transportation equipment promptly, and as close to the transportation time as possible • Transport chilled RTE food as soon as possible after loading into equipment • Hold chilled RTE foods transported to the service point in chilled equipment at 5°C or less or transfer to appropriate refrigeration at ward/pantry
For further guidance please follow the link to the Food Standards Agency Website.