Listeria

Introduction

Listeria is a family of bacteria that contains ten species. One of these, Listeria monocytogenes, causes the disease listeriosis.

Although listeriosis is rare, the disease is often severe with high hospitalisation and mortality rates. In the EU about 2,400 infections were reported in 2017.

People usually become ill with listeriosis after eating contaminated food.

Cooking at temperatures higher than 65C kills the bacteria. However, Listeria can contaminate foods after production (for example contamination can occur after the food is cooked but before is packaged). Unlike many other foodborne bacteria, Listeria tolerates salty environments and can even multiply at cold temperatures (between +2C and 4C).

The hardiness of these bacteria, coupled with the high mortality rates in humans, means that safe handling of food is paramount to ensure public health.

In infected people, symptoms vary, ranging from mild flu-like symptoms, such as nausea, vomiting and diarrhoea to more serious infections such as meningitis and other potentially life-threatening complications. The disease primarily affects the elderly, pregnant women, new-borns and people with weak immune systems.

Listeria monocytogenes can be found in many foods. Examples include smoked fish; meats; cheeses (especially soft cheeses) and raw vegetables.

To prevent listeriosis, it is important to follow good manufacturing practices, hygiene practices and effective temperature control throughout the food production, distribution and storage chain, including in the home. Consumers should keep the temperature of their refrigerators low to limit potential growth of bacteria such as Listeria, which may be present in ready-to-eat foods.

International organisations such as the World Health Organization advise that foods should be refrigerated below 5C.

Latest

In 2018 Member States reported 2,549 cases of listeriosis in humans. The group most affected by the disease in 2018 were the elderly, particularly those over 84.

The fatality rate from listeriosis was 15,6%. Listeria rarely exceeded the EU food safety limit in ready-to-eat food.

See: annual report on trends and sources of zoonoses published by EFSA and the European Centre for Disease Prevention and Control (ECDC)

Milestones

June 2018 EFSA provides scientific and technical assistance on sampling and testing strategies for the detection of L. monocytogenes in the processing plants of frozen vegetables.

Jan 2018 Experts provide scientific advice on Listeria monocytogenes and risks to public health from consumption of contaminated ready-to-eat food. They conclude that between 2008 and 2015 Listeria cases increased among two groups of the population: people over 75 and women aged 25-44 (believed to be mainly pregnancy-related).

June 2013 The first part of EFSA’s analysis of an EU-wide baseline survey on Listeria monocytogenes provides insights into the presence of this bacterium in certain ready-to-eat foods (fish, cold meats and soft cheeses). The proportion of food samples exceeding the legal food safety limit was low. However, given the popularity of these foods and the severe implications that listeriosis can have on human health, overall vigilance regarding the presence of the bacteria in food is warranted.

January 2008 Scientists update their advice on the Listeria risks in foods. They recommend that efforts to reduce risks to human health should focus on risk reduction practices both during the production process of ready-to-eat foods (RTE) and at home by consumers.

Role

EFSA assesses food safety risks posed by Listeria for human health and advises policy makers on possible science-based control and mitigation options. It does so by:

  • Monitoring the presence of Listeria monocytogenes in the food chain annually in EU Member States.
  • Assessing the prevalence and levels of Listeria monocytogenes in certain ready-to-eat foods across the EU (such as soft cheeses, cold meats and fish) which may contain this bacteria.
  • Analysing the risk factors responsible for the presence and growth of Listeria monocytogenes in foods.

EU framework

The monitoring and control of foodborne diseases as well as food hygiene requirements and food safety criteria are regulated by EU legislation.

Commission Regulation (EC) No 2073/2005 on microbiological criteria for foodstuffs lays down food safety criteria for certain important foodborne bacteria, including Listeria monocytogenes.