Listeria – What’s the fuss?

Currently there’s a lot of news surrounding an outbreak of Listeriosis which has resulted in the death of three patients in a Manchester hospital caused by the micro-organism Listeria monocytogenes.

So what is this bacteria and what steps should the food, dairy and beverage industries be taking to control it?

Listeria monocytogenes is only one strain of the Listeria “family” of bacteria which can commonly be found in cold, wet environments and in soil amongst other sources – however very few strains are dangerous or pathogenic. To the majority of the population L. monocytogenes is relatively low risk and may cause mild, flu like symptoms with little lasting effect. However, for vulnerable groups the story is very different with the elderly, the young, those with underlying medical conditions and pregnant women being at particular risk.

There is a generally held belief that refrigeration of food will prevent food poisoning bacteria from multiplying and for organisms such as Salmonella this is indeed the case – Listeria species, however, are able to continue to grow as low as -1º Celcius presenting a particular concern to food safety professionals.

To put the risks from this micro-organism into context, an outbreak in South Africa involving cooked meat in 2017 – 2018 resulted in over 1,000 consumers becoming ill with 204 of those losingtheir lives (including 80 who were less than 2 years old). A further outbreak in 2018 involved frozen sweetcorn which was distributed across Europe and resulted in 9 deaths.

In the UK, our enjoyment of chilled, ready to eat foods has resulted in extensive research and development of management controls to reduce the likelihood of Listeria monocytogenes being present in pre-packed foods bought from the chiller cabinet.  Indeed, under EU legislation the organism is specifically named as being required to be absent at the point of despatch and at less than 100 organisms per 25g at the end of the product’s shelf-life.  The controls employed in food processing establishments can include:

• Effective cleaning and disinfection regimes, in particular between product runs and during breaks.
• Assessment of food contact surfaces for the presence of bacterial contamination, for example using ATP technology or FreshCheck. It should be remembered that routine analysis of L. monocytogenes can take up to seven days so general hygiene indicators are often used to reduce the risks of contamination.
• Training and awareness amongst the operatives and management teams to ensure that Good Hygiene Practices (GHP) and Good Manufacturing Practices (GMP) are stringently followed to reduce the movement of the bacterium from reservoirs such as the floor and drains to food contact surfaces.
• Tight controls on movement between High Care / High Risk and Low Risk zones of the food processing environment.
• Correct flow of air, water and other services to avoid contamination being carried into High Care / High Risk areas.

For more information on the on-going investigation into the outbreak in Manchester please visit the Food Standards Agency web-site (www.food.gov.uk). For more assistance, information on training or on testing technologies then contact your local Christeyns Food Hygiene Technical Account Manager.