1. Listeria monocytogenes in food as public safety risk
European
Symposium on
Food Safety
21-23 May 2012
Listeria monocytogenes in food as public safety risk
Grzegorz Madajczak, Ph.D. DVM

2. The goal of this presentation:
Present, that Listeria monocytogenes it is not only
the food quality / safety criterion,
but first of all public health risk.

3. Listeria monocytogenes
Gram(+) bacteria.
Regular, short rods with rounded ends.
Facultative anaerobes.
Can grow at refrigeration temeratures to significant numbers (in sufficient time).
Resistant for low pH.
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4. Listeria monocytogenes
The primary reservoir for L. monocytogenes is soil, water and forage, mud, and silage.
Additional reservoir is alimentary tract of domestic and wild animals.
Source of bacteria are infected animals.
Consumption of contaminated food is main route of infection for human.
Infectious dose was determined as 107 CFU. Other papers suggest even 100 CFU.
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5. Listeriosis Infectious disease, caused by Listeria monocytogens.
Especially danger for some groups of people (high risk groups):
Neonates,
Pregnant women,
Immunocompromised people,
Elderly (60.2 % of cases in 2010 occurring in individuals over the age of 65).

6. Age and gender distribution of listeriosis
High number of
pregnancy associated cases
Data Source: ECDC TESSY

7. Transmission of L. monocytogenes
Reservoir
Source
Vehicle
Transplacentar
infections

8. L. monocytogenes in food procesing and retail
L. monocytogenes is frequently present in raw foods of both plant and animal origin.
Can be endemic in food processing environment.
Present in food retail environment and houshold.
“From farm to fork”

9. Invasive listeriosis Notificable disease.
Varied clinical forms are described:
Sepsis,
CNS infections,
Endocarditis,
Localised infections,
Pregnancy associated infections

10. Gastrointestinal listeriosis
Usually self-limiting febrile gastrointestinal disease presenting with unspecific symptoms like:
Nausea,
Vomiting,
Diarrhea.
Observed as sporadic cases and food-poisoning outbreaks.

11. Sporadic Listeria Gastroenteritis ?
Study conducted by Walter F. Schlech III in 2002 in Canada.
Material: stool spec. from 7775 diarrhea cases.
Only 18 cases were caused by L. monocytogenes.
L. monocytogenes could cause the sporadic gastroeteritis, but it is not importanant pathogen in such cases.
Schlech et al., CID 41 (2005),

12. Outbreaks of listeriosis
Food-borne outbreak: „an incidence, observed under given circumstances, of two or more human cases of the same disease and/or infection, or a situation in which the observed number of human cases exceeds the expected number and where the cases are linked, or are probably linked, to the same food source”.
(Directive 2003/99/EC)
Food vehicle: food (or foodstuff) that is contaminated by a causative agent.
(EFSA, Manual for reporting of food-borne outbreaks […])

13. Outbreaks of listeriosis
Listeria monocytogenes is absolute foodborne pathogen, caused both: gastrointestinal and invasive listeriosis.
All listeriosis outbreaks should be classified as foodborne or at least waterborne.

14. Outbreaks of listeriosis
Country
Year
Food vehicle
Affected
France
Pork tongue in jelly
26 cases
USA (multistate)
Mexican-style cheese made from pasteurized milk
8 pregnant women
Czech Rep.
2006
Local cheese
75 cases
Canada, Quebec
2008
Pasteurized milk cheese
14 pregnant women, 2 babies born to asymptomatic carriers
Austria, Germany, Czech Rep.
2009
Acid curd cheese “Quargel”
14 cases, 4 deaths
USA, Louisiana
2010
Hog head cheese
14 cases of invasive listeriosis
2011
Cantaloupe (Rockmelon)
84 people, 15 deads
In 2012 year 37 alerts were notified in RASFF
In 2011 year 106 alerts were notified in RASFF

15. Pregnancy associated listeriosis
Case classification: illness occurred in a pregnant woman or an infant aged <28 days.
Woman has unspecific flu-like symptoms.
CNS infection are very rare in pregnant women.
Outcome depends on stage of pregnancy.
I trimester
II trimester
III trimester
Congenital listeriossis
Preterm birth
Stillbirth
Miscarriage

16. Congentital listeriosis
Depending on time of clinical symptoms manifestation, two types of infection are recognized
Early-onset
Late-onset
Associated with prematurity and acquired throw utero.
Caused by bacteria acquired from vaginal tract of asymptomatic mothers
Clinical symptoms occurs just after birth (mean-time is 1.5 day)
Occurs about 2 weeks post partum.
Sepsis
Meningitis

17. Severity of listeriosis
Characterization of listeriosis severity depends on category of disease (invasive / non-invasive).
Low occurrence contrasts with high case-fatality rate (ranging 20-30%).
Up to 11% of neonates and 30% survivor of CNS infections suffer residual symptoms.
Psychiatric squeals have been also reported.
Also psychological aspects
Losing pregnancy
Neonatal deaths

18. Listeriosis in Europe

19. Listeriosis in Europe
The EU/EEA rate of confirmed human cases of Listeria infection has been relatively stable in the last four years.
Listeriosis had the highest impact among the elderly (65+) with the highest confirmed case rates and high mortality.
Data Source: ECDC TESSY

20. Listeriosis in Europe Listeriosis cases in 2010 by country
Data Source: ECDC TESSY

21. Listeriosis in Poland Listeriosis cases Neonatal listeriosis
Data Source: Infectious diseases and poisonings in Poland

22. Listeria monocytogenes – food safety criterions
EU Regulation No 2073/2005 lays down food safety criteria for L. monocytogenes in RTE foods:
In RTE food for infants and special medical purposes L. monocytogenes must not be present in 25 g,
L. monocytogenes must not be present in levels above 100 cfu/g during the shelf life of other RTE products.

23. Listeria monocytogenes – food safety criterions
RTE foods that NOT SUPPORT the growth of the bacterium
L. monocytogenes must not be present in levels above 100 cfu/g during the shelf life.

24. Listeria monocytogenes – food safety criterions
RTE foods that SUPPORT the growth of the bacterium
L. monocytogenes must not be present in 25 g at the time of leaving the production plant;
however, if the producer can demonstrate, that the product will not exceed the limit of cfu/g throughout shelf life this criterion does not apply.

25. USA FSIS L. monocytogenes “zero tolerance” politic in RTE
Formed as result of increased number of listeriosis in ’s in USA after consumption of deli meats and other processed products.
Zero tolerance - no detectable level of L. monocytogenes in RTE food products permitted.
One of long-term initiatives was to conduct a risk assessment for L. monocytogenes together with FDA.

26. Risk assessment to public health from foodborne L. monocytogenes
The goal was to predict the relative public health impact of foodborne Listeria monocytogenes from selected 23 food categories.
RTE foods to asses were chosen, if had a history of either Listeria monocytogenes contamination or were implicated epidemiologically.
This risk assessment have been used as base for FAO WHO reccomendations.

27. Risk assessment - results
Decreased Risk per Annum
Deli Meats
Frankfurters (not reheated)
No food categories
Deli-type Salads
Dry/Semi-dry Fermented Sausages Frankfurters (reheated)
Fresh Soft Cheese Fruits Semi-soft Cheese Soft Ripened Cheese Vegetables
Cooked RTE Crustaceans
High Fat and Other Dairy Products
Pasteurized Fluid Milk
Soft Unripened Cheese
Pâté and Meat Spreads
Unpasteurized Fluid Milk
Smoked Seafood
Decreased Risk per Serving
Preserved Fish
Raw Seafood
No food categories
Cultured Milk Products
Hard Cheese
Ice Cream and Other Frozen Dairy Products
Processed Cheese
Very high risk
High risk
Moderate risk
Low risk
Very low risk

28. Foods of very high risk Includes two food categories:
Deli Meats,
Frankfurters, Not Reheated.
They have high predicted relative risk rankings on both a per serving and per annum basis, because:
Have relatively high rates of contamination.
Support the relative rapid growth of Listeria monocytogenes under refrigerated storage.
Are stored for extended periods.
Are consumed extensively.
These products have also been directly linked to outbreaks of listeriosis.
This risk designation is one that is consistent with the need for immediate attention in relation to the national goal for reducing the incidence of foodborne listeriosis. Likely activities include the development of new control strategies and/or consumer education programs suitable for these products.

29. Very low risk food products
Includes four food categories:
Cultured Milk Products,
Hard Cheese,
Ice Cream and Other Frozen Dairy Products,
Processed Cheese.
These products all have in common the characteristics of being subjected to a bactericidal treatment, having very low contamination rates, and possessing an inherent characteristic that either inactivates Listeria monocytogenes (e.g., Cultured Milk Products, Hard Cheese) or prevents its growth (e.g., Ice Cream and Other Frozen Dairy Products, Processed Cheese).
This results in a very low predicted per serving relative risks. The predicted per annum relative risks are also low despite the fact that these products are among the more commonly consumed RTE products considered by the risk assessment.
The results of the risk assessment predict that unless there was a gross error in their manufacture, these products are highly unlikely to be a significant source of foodborne listeriosis.

30. EU initiative for L. monocytogenes reduction in RTE foods
European Comission launched the survey on Listeria monocytogenes in selected categories of ready-to-eat food at retail in the EU.
RTE food categories under investigation:
Smoked and gravad fish,
Soft and semi-soft cheeses,
Heat-treated meat products.
Analyses methods:
L. monocytogenes detection and enumeration,
pH and aw measurement,

31. Reduction of risk to public health from foodborne L. monocytogenes

32. Summary Listeriosis is serious infectious foodborne disease.
Many factors affect on risk of listeriosis.
Food producers have not influence on many of them.
Initial quality of food - no Listeria at detectable level is the best method to increase the food safety.

33. References: