listeria monocytogenes in food as public safety risk

National Public Health Institute – National Institute of Hygiene

Listeria monocytogenes in food as public safety risk

Grzegorz Madajczak, Ph.D. [email protected]

EuropeanSymposium on

Food Safety21-23 May 2012

2014-09-30 2National Public Health Institute – National Institute of Hygiene

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.


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.

The image source:http://www.sciencephoto.com/


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. The image source:

http://emedicine.medscape.com/article/965841-overview


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).


Age and gender distributionof listeriosis

Data Source: ECDC TESSY

<1 1-9 10-19 20-29 30-39 40-49 50-59 60-69 70-79 80+0

200

400

600

800

1000

1200

FemaleMale

High number ofpregnancy associated cases


Transmission of L. monocytogenes

Reservoir Source VehicleTransplacentar

infections


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”


Invasive listeriosis• Notificable disease.• Varied clinical forms are described:– Sepsis,– CNS infections,– Endocarditis,– Localised infections,

– Pregnancy associated infections


Gastrointestinal listeriosis• Usually self-limiting febrile gastrointestinal disease

presenting with unspecific symptoms like:– Nausea,– Vomiting,– Diarrhea.

• Observed as sporadic cases and food-poisoning outbreaks.


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.

1813 2

1 4

137

140L. monocytogenesL. innocuaL. welshimeriL. grayiother ListeriaSalmonella sp.Campylobacter sp.

Schlech et al., CID 41 (2005), 778-784


Outbreaks of listeriosisFood-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 […])


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.


Outbreaks of listeriosisCountry Year Food vehicle Affected

France 1999-2000 Pork tongue in jelly 26 casesUSA (multistate) 2008-2009 Mexican-style cheese made

from pasteurized milk 8 pregnant women

Czech Rep. 2006 Local cheese 75 casesCanada, Quebec 2008 Pasteurized milk cheese 14 pregnant women, 2 babies born to

asymptomatic carriersAustria, Germany, Czech Rep.

2009 Acid curd cheese “Quargel” 14 cases, 4 deaths

USA, Louisiana 2010 Hog head cheese 14 cases of invasive listeriosis

USA (multistate) 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


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


Congentital listeriosis

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

• Depending on time of clinical symptoms manifestation, two types of infection are recognized


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.

• Losing pregnancy• Neonatal deaths

Also psychological aspects


Listeriosis in Europe2%

4%

58%

1%

16%

14%

2%

4%

Number of RASFF alerts in 2010 year

bivalve molluscs and products thereof

crustaceans and products thereof

fish and fish products

gastropods

meat and meat products (other than poultry)

milk and milk products

poultry meat and poultry meat products

prepared dishes and snacks


Listeriosis in Europe

• The EU/EEA rate of confirmed human cases of Listeria infection has been relatively stable in the last four years.


2006 2007 2008 2009 2010130013501400145015001550160016501700

00.050.10.150.20.250.30.350.4

1654

1425

1581 1597 1637

0.350.3

0.34 0.36 0.37

No of cases Notification rate

• Listeriosis had the highest impact among the elderly (65+) with the highest confirmed case rates and high mortality.


Listeriosis in Europe

DE FR UK ES IT NL FI SE DK PL BE AT CZ NO HU SI GR IE LV RO EE LT SK BG CY IS MT0

50

100

150

200

250

300

350

400390

312

176

12995

72 71 63 62 5940 35 29 22 20 11 10 10 7 6 5 5 5 4 1 1 1

Listeriosis cases in 2010 by country



Listeriosis in Poland

2005 2006 2007 2008 2009 2010 20110

20

40

60

0

0.05

0.1

0.15

0.2

22 2843 33 33

62 640.058 0.058

0.110.09 0.09

0.17 0.17

Cases Morbidity per 100 000

2005 2006 2007 2008 2009 2010 20110

2

4

6

8

10

0

0.5

1

1.5

2

2.5

31

5

0

6 680.84

0.27

1.29 1.44 1.45

1.94

Neonatal cases Morbidity per 100 000 of births

Listeriosis cases

Neonatal listeriosis

Data Source: Infectious diseases and poisonings in Polandhttp://www.pzh.gov.pl/oldpage/epimeld


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.


• L. monocytogenes must not be present in levels above 100 cfu/g during the shelf life.

RTE foods that NOT 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 100 cfu/g throughout shelf life this criterion does not apply.

RTE foods that SUPPORT the growth of the bacterium


USA FSIS L. monocytogenes“zero tolerance” politic in RTE

• Formed as result of increased number of listeriosis in 1980-90’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.


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.

Cultured Milk ProductsHard Cheese

Ice Cream and Other Frozen Dairy Products

Processed Cheese

Preserved FishRaw Seafood

No food categories

High Fat and Other Dairy ProductsPasteurized Fluid MilkSoft Unripened Cheese

Pâté and Meat SpreadsUnpasteurized Fluid MilkSmoked Seafood

No food categories

Deli-type SaladsDry/Semi-dry Fermented Sausages

Frankfurters (reheated)Fresh Soft Cheese Fruits Semi-soft

Cheese Soft Ripened Cheese Vegetables

No food categories

Cooked RTE Crustaceans No food categories

No food categoriesDeli MeatsFrankfurters (not reheated)

Dec

reas

ed R

isk

per S

ervi

ng

Decreased Risk per Annum

Moderate riskHigh risk Low riskVery high risk Very low risk

Risk assessment - results


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.


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.


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,


Reduction of risk to public health from foodborne L. monocytogenes


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.


•References: •www.slideshare.com

listeria monocytogenes in food as public safety risk

Documents

public health risk

food procesing

food retail environment

food processing environment

diarrhea cases

sporadic cases

foodpoisoning outbreaks

source of bacteria