October 17th, 2018
Salmonella, Listeria: avoiding outbreaks with Environmental Monitoring Program (EMP)

Environmental Monitoring Program (EMP) is the “must have” to control pathogens such as Salmonella and Listeria in processing environments of food facilities.

In 2017, more than 300 food recalls in the European Union and United States were related to foodborne pathogens such as Salmonella and Listeria monocytogenes. As a consequence, one person out of ten gets ill every year because of contaminated food. Official agencies are shifting the emphasis from testing end products to testing environmental samples, leading to additional product recalls. Therefore, it is crucial for food manufacturing companies to develop an efficient Environmental Monitoring Programs and initiate preventive controls in their facilities.

Product contamination can occur at any stage of a food chain

According to the European Food Safety Agency (EFSA), bacteria such as Salmonella and Listeria monocytogenes can cause foodborne illness to consumers in contact with contaminated food or water.

High risk foods include animal products (e.g. raw turkey products, raw eggs for Salmonella; raw milk cheese for Listeria), water and also foods of vegetal origin (e.g. fruits and vegetables for Salmonella).

The induced infectious diseases are respectively called salmonellosis and listeriosis. They are zoonoses, which means that they can be transmitted between animals and humans.

EFSA states that salmonellosis was the first cause of foodborne outbreaks in the European Union in 2016 with 1,067 Salmonella outbreaks reported. While the number of persons infected with Salmonella tended to decline until 2014, it leveled off between 2014 and 2016 (+3%). With 2,536 cases in 2016, listeriosis is much less widespread but not less severe. In fact, its fatality rate is the highest in the EU: 16,2% of infected people with Listeria monocytogenes died in 2016. Moreover, a statistical increase has been reported since 2008.

According to the World Health Organization (WHO), symptoms associated with salmonellosis are fever, abdominal cramps, diarrhea, nausea and sometimes vomiting. It can strongly impact immune systems of both elderly and young children and  can lead to dehydration, hospitalization and death. Salmonellosis may occur from 6 to 72 hours after the consumption of contaminated products and generally lasts 2 to 7 days.

Listeriosis is most of the time associated with flu-like symptoms. However, it is a public health concern for sensitive populations as pregnant women: listeriosis can lead to miscarriage, stillbirth, premature delivery, or life threatening infection of the newborn.

Listeriosis may occur from 3 to 70 days after the consumption of contaminated products and lasts days to weeks.

Listeria monocytogenes and Salmonella are particularly involved in food product recalls due to their specific surviving and residence properties. In fact, Listeria monocytogenes has a growth potential in cool and wet environments whereas Salmonella can survive in warm and dry environments. For these reasons these bacteria can survive in production environments and raw materials and can contaminate (or recontaminate) food goods. Contamination hot-spots can be found all along a food production line, from the import of contaminated raw materials in a food factory to  wet areas in the facility.

An efficient EMP can prevent and solve bacterial contaminations

An Environmental Monitoring Program (EMP) is a risk assessment methodology based on the “seek and destroy” approach:

●     “Seek”: digging deep within the equipment, often involving careful disassembly of the equipment and sampling,

●     “Destroy”: finding the root cause of the contamination and fixing permanently the issue.

This methodology may be used to verify the effectiveness of sanitation and mitigate potential harborage and growth niches in the equipment. The principles of an efficient EMP are based on :

●     Risk assessment: checking contamination sources,  traffic patterns and quality of monitoring

●     Being aware and warned of the potential presence of biofilms: functional group of organisms which presents two major issues (speed of formation and maturation and the ability to withstand the pressure of conventional cleaning and disinfectants),

●     The importance of zoning into four different zones. These zones differentiate areas within the manufacturing facility, based on microbiological risk.

The understanding of these EMP pieces will result in the identification of the most relevant sampling points in the production environment, therefore helping you in avoiding food contamination.

You want to know more about Environmental Monitoring?

Download our free eBook on Environmental Monitoring to find out more about :

- The legislation in Europe and the US

- How to conduct an exhaustive and adapted risk assessment

- How to manage generated data from test results

- How to differentiate manufacturing areas based on microbiological risk

- How to use historical data to select relevant sampling points

- The scheme to adopt for an adapted sampling plan

- Best practices regarding sampling techniques

- Corrective actions to implement


European Food Safety Agency (EFSA), ‘Salmonella cases no longer falling in the EU’, December 2017.

Center for Disease Control and Prevention, ‘Salmonella and Food’, July 2017.

EFSA, ‘Factsheet: Listeria’, February 2018.

World Health Organization (WHO), ‘Factsheet: Salmonella (non-typhoidal)’, January 2018.

EFSA, ‘Listeria infections increase in vulnerable groups’, January 2018.

EFSA, ‘EFSA explains zoonotic diseases: Salmonella’, 2014.

EFSA, ‘The European Union summary report on trends and sources of zoonoses, zoonotic agents and foodborne outbreaks in 2016’, December 2017.

European Commission, ‘RASFF - Food and Feed Safety Alerts’, [online].

FDA, ’Recalls, Market Withdrawals, & Safety Alerts’, [continuously updated].

FoodSafey.gov, ‘’Listeria’, [online].



Christophe Dufour 

Doctor of Veterinary Medicine
Scientific Director Microbiology Europe for Mérieux NutriSciences

Christophe has worked in different food testing laboratories over the past 30 years. He participated to various normalization groups and expert panels (AFNOR, ANSES, IAFP, ILSI ) in the field of food microbiology, microbiological criteria, food quality, GMO or Allergens issues. Christophe contributes to many working groups with professional to develop process criteria for food industry and conducts risk assessments in multiple food industry and catering facilities.

In many food safety incidents caused by environmental contamination, a great deal of information was available, but it was not being correctly analyzed or interpreted. Proper EMP design, implementation and execution can solve this issue.

Christophe Dufour


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