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Presence and Survival of Listeria monocytogenes in Food Chain

22 February 2014

The incidence rate of listeriosis is higher in Finland than on average across Europe according to research findings delivered to a special food safety seminar.

Special Researcher, Dr Annukka Markkula, who works in the Food and Feed Microbiology Research Unit of Finnish Food Safety Authority Evira, told the seminar in Helsinki that the foodborne pathogen Listeria monocytogenes is able to cause a life threatening disease, listeriosis, to susceptible people.

In Europe, USA, and Australia, approximately 0.3 listeriosis cases/100 000
persons are reported annually.

In Finland, the incidence is higher and between 2010 and 2012 0.8 - 1.4 cases/100 000 persons (43 - 71 cases) were reported each year.

During 2013, by the end of November, a total of 55 cases have been reported in the country.

Listeriosis is typically detected in people with decreased cell mediated immunity because of another serious disease, high age, or pregnancy and typical symptoms include meningitis, encephalitis, sepsis, and abortion, according to Dr Markkula.

Approximately one third of these invasive listeriosis cases are fatal.

In previously healthy adults and children the disease is rare and symptoms of mild gastrointestinal are detected.

The development of listeriosis seems to be dose dependent and low numbers of the bacterium in fresh produce and in foods that undergo heat treatment are considered as safe.

Foods that may pose risk of listeriosis to consumers include ready-to-eat foods that enable the growth of the bacterium during long shelf lives, for example fermented and cold smoked meat and fish products and dairy products made from non-pasteurised milk.

The foods may be contaminated by widespread L. monocytogenes already before harvest, but the main source of contamination has been reported to be endogenous strains of the processing environment.

Listeria may persist in food processing plants for years.

Its ability to form biofilm and adapt to various stressful environmental conditions may help it to persist in processing environment and grow in foods.

The growth has been reported in temperatures from -1.5°C to approximately 45°C, at pH range of 4.3 - 9.6 and higher than 10% salt, but it may survive even more extreme conditions.

Stress exposure results in changes in numerous factors of the bacterial cell.

Understanding the roles and mechanisms of these factors may provide new insights to the control of L. monocytogenes and listeriosis, according to Dr Markkula.


December 2013

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