Keeping Salmonella out of the food chain

Danièle Sohier (PhD), is the Global Scientific Affairs Senior Manager for Microbiology at Thermo Fisher, and President Elect of AOAC International for 2023-2024.

Danièle coordinates collaboration with governing bodies, research organizations, laboratory and food safety managers. She is honored to support global food safety and public health, and therefore she serve in multiple activities and working groups within AOAC, ISO and MicroVal.

Danièle Sohier

Despite our understanding of how Salmonella proliferate in our food manufacturing processes, the bacteria still cause millions of illnesses and hundreds of deaths every year. Because even the smallest misstep in safety testing procedures can open the door to a potential infection.

With the microscopic pathogen representing such a macroscopic threat to both public and business health, proactive and robust processes are the only way to keep the threat at bay.

In this special Spotlight, we take a deep dive into Salmonella, its serotypes and prevalence, and how to keep it out of your facilities, your products, and your customers.

What is Salmonella?

Salmonella are one of the most common causes of food-borne diseases worldwide1. The ubiquitous and hardy bacterium, which can survive several weeks in a dry environment and several months in water,2 can cause serious illness if ingested. Different serotypes, for example, can cause salmonellosis, typhoid fever, paratyphoid fever, and even death.

Two species, Salmonella bongori and Salmonella enterica, and more than 2,500 serotypes have so far been identified1

Salmonella serotypes are often grouped in “non-typhoidal” and “typhoidal”: 

  • Typhoidal Salmonella, which include Salmonella Typhi and Salmonella Paratyphi, can cause typhoid fever and paratyphoid fever, and typically spread via the fecal-aural route of infection.1

  • Non-typhoidal Salmonella, such as Salmonella Enteritidis, Salmonella Typhimurium, and Salmonella Newport, can cause salmonellosis gastroenteritis. They tend to spread via contaminated food.4

Within days of consuming the bacteria, people can experience diarrhea, fever, and stomach cramps. And while may recover without treatment or are treated successfully with antibiotics, others can go on to develop serious complications as the infection spreads into their bones or nervous system.5 Children, older people and those with compromised immune systems are most at risk of serious disease. 

 Salmonella diagram 
 Two species, Salmonella bongori and Salmonella enterica, and more than 2,500 serotypes have so far been identified1 
  • In the US, CDC estimates there are 1.35 million Salmonella infections, 26,500 hospitalizations, and 420 deaths from every year6

  • Across Europe in 2019, 170 people died following a Salmonella infection7

  • Salmonella costs healthcare systems an estimated $357 million every year8

Salmonella in the food manufacturing process

Infection with Salmonella is one of our most common and important zoonoses: disease or infection that can spread between animals and humans. Salmonella bacteria can live in the intestines of animals, including livestock, and they are widely distributed in the environment. Therefore, the most common sources of Salmonella are chicken, beef, pork, eggs, fruits, vegetables9, If soil, water, farmer tools come into contact with animal feces, they can transfer Salmonella to fruits and vegetables. Salmonella is as well known for being able to survive in dry conditions in food products and production environment for a long period of time. Over the past years, several foodborne outbreaks have been reported with Salmonella in various low-moisture foods such cocoa and chocolates10, flour, milk powders and infant formula11.

The most common illness-causing Salmonella serotypes vary depending on the region of the world. However, Europe and North America share some similarities12,13.

Among the 2,500 Salmonella serotypes, S. Enteritis, S. Typhimurium, monophasic variant of S. Typhymutrium, S. Infantis, S. Derby. S. Kentucky, S. Anatum are showing high prevalence in poultry and eggs, beef and pork. However, all these serotypes do not have the same impact on public health, S. Enteritidis, S. Typhimurium including monophasic variants having the highest impact.

Producers worldwide are obliged to comply with strict food safety testing requirements that are designed to protect public health from the dangers of Salmonella. The US and European Union, for example, both have poultry-focused programs that track the serotypes S. Enteritidis and S. Typhimurium, which, along with Salmonella Infantis account for around 80% of recorded infections,14 from farm to fork.

The bacteria can enter food products from multiple points of contamination, from raw materials to the processing environment.  As such, each of step must be tested regularly as part of a proactive, robust food safety program that covers:

  • raw materials

  • environment

  • ingredients / products during processing

  • post processing

  • pre-market release 

While there is no doubt that such measures are necessary, they can present operational challenges. Standard testing methods, such as the Kauffmann-White serotyping workflow, can take two or three days to return a result. This can slow down production lines and eat into precious shelf life, ultimately cutting into the bottom line.

Be sure with the Thermo Scientific™ SureTect™ PCR System

Thermo Scientific™ SureTect™ PCR System

Laboratories the world over are now turning to polymerase chain reaction (PCR) testing for quick, accurate results that provide all the information they need to keep a lid on outbreaks throughout production. 

The Thermo Scientific™ SureTect™ Salmonella Species Assay workflow can recover just small numbers of injured Salmonella cells and grow them to a detectable level, even in challenging matrices like cocoa. 

Thermo Fisher is also able to offer two Salmonella serotype-specific PCR assays:

  • Thermo Scientific RapidFinder Salmonella Multiplex Assay, which detects all Salmonella species, as well as differentiating between S. Enteritidis and S. Typhimurium in less than 24 hours.

  • Thermo Scientific™ SureCount™ Salmonella Multiplex Assay for simultaneous quantification of the same Salmonella targets in around eight hours. 

These multiplex PCR Assays can be powerful tools for meat and poultry businesses when used as part of a robust Salmonella control program.


Want to learn about Salmonella test methods for food testing laboratories?

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  1. Diep, B., Barretto, C., Portmann, A. C., Fournier, C., Karczmarek, A., Voets, G., ... & Klijn, A. (2019). Salmonella serotyping; comparison of the traditional method to a microarray-based method and an in silico platform using whole genome sequencing data. Frontiers in microbiology, 10, 2554. l
  2. WHO. Salmonella (non-typhoidal). (2018). Available at: 
  3. Cheng, R. A., Eade, C. R., & Wiedmann, M. (2019). Embracing diversity: differences in virulence mechanisms, disease severity, and host adaptations contribute to the success of nontyphoidal Salmonella as a foodborne pathogen. Frontiers in microbiology, 10, 1368.
  4. CDC. Typhoid Fever and Paratyphoid Fever: Questions and answers. (2020). Available at: 
  5. Salmonella: Information for Healthcare Professionals and Laboratories. (2020). Available at:,Typhimurium,%20Newport,%20and%20Javiana  . Last accessed: 8 June 2023
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  9. CDC. Salmonella and Food. (2023) 
  10. Food Manufacture. Salmonella spp. in chocolate: Lessons 2022 taught us. (2022). Available at:[1]outbreaks-in-chocolate-factories-one-year-on#    June 2023
  11. CDC. Salmonella Outbreak Linked to Flour. (2023). Available at: 
  12. Food Safety News. The Big Five: Most Common Salmonella Strains in Foodborne Illness Outbreaks. (2013). Available at: 
  13. Hindermann, D., Gopinath, G., Chase, H., Negrete, F., Althaus, D., Zurfluh, K., ... & Nüesch-Inderbinen, M. (2017). Salmonella enterica serovar Infantis from food and human infections, Switzerland, 2010–2015: poultry-related multidrug resistant clones and an emerging ESBL producing clonal lineage. Frontiers in Microbiology, 8, 1322.
  14. EFSA Panel on Biological Hazards (EFSA BIOHAZ Panel), Koutsoumanis, K., Allende, A., Alvarez‐Ordóñez, A., Bolton, D., Bover‐Cid, S., ... & Davies, R. (2019). Salmonella control in poultry flocks and its public health impact. Efsa Journal, 17(2), e05596.