Salmonella: An ever-present Food Industry Concern
In the food industry, Salmonella stands out as a notorious problem, causing a widespread bacterial infection known as salmonellosis. This genus of bacteria poses a significant public health threat globally, responsible for approximately 1.35 million infections, 26,500 hospitalizations, and 420 deaths annually in the United States alone1. In Europe, Salmonella remains a significant concern as in 2022, there were 65,967 laboratory-confirmed cases of salmonellosis in the EU2. The notification rate was 15.5 cases per 100,000 population being the second most reported gastrointestinal disorder in the EU. Symptoms include gastroenteritis, abdominal cramps, bloody diarrhea, fever, myalgia, headache, nausea and vomiting2. These numbers highlight the importance of vigilance and proper food safety practices to prevent outbreaks and protect public health. The release of contaminated foods can lead to severe consequences such as processing delays, product recalls, plant shutdowns, and even legal actions.
Food sources of Salmonella included mainly milk, eggs, meat (poultry, beef) vegetables, and fresh fruits. Recent outbreaks highlight the ongoing risks. In 2024, a multistate outbreak in the United States linked to fresh basil resulted in numerous illnesses3. Similarly, a 2023 outbreak associated with raw cookie dough led to significant public health concerns4. In 2022, nearly 200 people in the EU and UK fell ill due to a Salmonella outbreak linked to contaminated food products, with several hospitalizations and at least one death5.
Consumers can protect themselves from Salmonella contamination by practicing good hygiene, such as washing hands with soap and water before and after handling food, after using the bathroom, and after touching animals or their environments6. It is also important to regularly clean kitchen surfaces, utensils, and cutting boards with hot, soapy water. Safe food handling is crucial; this includes keeping raw meat, poultry, seafood, and eggs separate from other foods to prevent cross-contamination, cooking foods to the appropriate temperatures (for example, poultry should be cooked to an internal temperature of 165°F or 74°C), and refrigerating or freezing perishable foods within two hours (or one hour if the temperature is above 90°F or 32°C).
The financial toll on food companies can be immense, impacting revenue, reputation, stock value, and overall profitability. To mitigate these risks, timely and accurate testing for Salmonella in food products is paramount. Implementing rigorous testing protocols not only helps in preventing outbreaks but also ensures consumer trust and safety.
Challenges of Traditional Methods: Bacterial Culture & Immunoassays
Historically, Salmonella spp. testing in the food industry has relied on labor-intensive and time-consuming methods such as culture-based and immunoassay techniques. Culture-based methods, while considered the gold standard and reference method, involve lengthy incubation periods—sometimes up to 5 days—before results are obtained. Moreover, the interpretation of results from culture-based tests can be subjective, introducing potential errors.
Similarly, immunoassay methods, while faster than culture-based techniques, still have limitations. These methods can take up to 2 days to yield results and may lack specificity due to interference from antibody binding.
Why is Real Time PCR a promising alternative in Food Microbiology ?
Considering these drawbacks, the application of rapid microbiology methods, specifically DNA testing using Real-Time PCR, has emerged as a game-changer in Salmonella spp. detection.
1.Improved Sensitivity (LOD)
Real-Time Polymerase Chain Reaction (PCR) technology offers a rapid and highly reliable method for detecting low levels of Salmonella in a wide range of food types with exceptional specificity. Real-Time PCR works by amplifying the DNA of the target pathogen — in this case, Salmonella — with remarkable sensitivity.
2. Lower Turnaround Time (TAT)
PCR-based methods can detect Salmonella DNA within hours, significantly reducing the time required for verdict. This rapid turnaround is crucial for timely decision-making in food safety management, allowing for quicker responses to potential contamination events and reducing the risk of widespread outbreaks. PCR methods are highly sensitive and specific, capable of detecting even low levels of Salmonella in various sample types, including food, water, and environmental samples7. Moreover, PCR-based testing enhances the accuracy of Salmonella detection. Traditional methods can sometimes yield false negatives due to the presence of competing microorganisms or suboptimal growth conditions. PCR circumvents these issues by directly targeting the genetic material of Salmonella, ensuring reliable detection7.
Implementing Real Time PCR with accredited method equivalence
The adoption of rapid microbiology methods, such as PCR, requires however rigorous validation and certification to ensure their reliability and acceptance. Third-party certification plays a crucial role in this process. Certification bodies, such as MicroVal and AOAC INTERNATIONAL, provide independen validation of these methods according to international standards like EN ISO 161408. This validation process ensure that PCR methods meet stringent criteria for accuracy, sensitivity, and reproducibility. This involves rigorous evaluations, including inclusivity/exclusivity testing, product consistency, stability, robustness, and matrix studies. This certification not only enhances the credibility of the testing methods but also provides companies and laboratories with confidence in their testing protocols, ultimately helping to protect public health and maintain consumer trust.
Embracing the future, reliably
In the realm of food safety, the importance of rapid and accurate testing for Salmonella cannot be overstated. Embracing innovative technologies like Real-Time PCR empowers food companies and testing laboratories to proactively mitigate the risks posed by this harmful foodborne pathogen. By leveraging the speed, accuracy, and efficiency of Real-Time PCR, businesses can uphold their commitment to quality and safety while safeguarding both consumer health and their bottom line.
REFERENCES
- https://www.cdc.gov/Salmonella/outbreaks.html
- https://www.ecdc.europa.eu/en/publications-data/salmonellosis-annual-epidemiological-report-2022
- https://www.foodsafetynews.com/2024/04/melissas-brand-organic-fresh-basil-added-to-recall-linked-to-salmonella-illnesses/
- https://www.foodsafetynews.com/2022/12/nearly-200-sick-in-eu-and-uk-Salmonella-outbreak/
- https://www.washingtonpost.com/wellness/2023/05/25/raw-cookie-dough-salmonella-illness/
- Ehuwa O, Jaiswal AK, Jaiswal S. Salmonella, Food Safety and Food Handling Practices. Foods. 2021 Apr 21;10(5):907. doi: 10.3390/foods10050907.
- Siala M, Barbana A, Smaoui S, Hachicha S, Marouane C, Kammoun S, Gdoura R and Messadi-Akrout F. Screening and Detecting Salmonellain Different Food Matrices in Southern Tunisia Using a Combined Enrichment/Real-Time PCR Method: Correlation with Conventional Culture Method. Front. Microbiol. 2017; 8:2416. doi: 10.3389/fmicb.2017.02416.
