This article applies to eggs and egg products what is explained in Salmonella: characteristics, detection and control and complements Salmonella in chicken meat and poultry products.
Table of contents
Why eggs are a different matrix
Shell eggs reach the consumer raw, and part of what is made with them (mayonnaise, desserts, undercooked eggs) is never fully cooked. On top of that comes a biological peculiarity: Salmonella can not only soil the shell, it can also end up inside the egg before the shell is formed. That is why its regulation has little in common with that of poultry meat, as a comparison with Salmonella in chicken meat and poultry products shows.
European data explain the attention it receives. In the EFSA and ECDC One Health report with 2024 data, Salmonella in eggs and egg products was the agent-food pair of greatest concern: first in number of strong-evidence outbreaks (83, compared with an average of 61.3 per year between 2020 and 2023) and in hospitalizations (138), and fourth in number of cases (748). S. Enteritidis, the serovar most closely linked to laying hens, caused 58.4 % of human cases acquired in the EU. The basics of the pathogen are covered in Salmonella: characteristics, detection and control.
Two contamination routes: vertical and through the shell
Vertical or transovarian transmission
FDA summarizes it in the 2009 final rule that created the Egg Safety Rule: S. Enteritidis can infect the ovaries and oviduct of some hens and contaminate the inside of the egg while it is still in the bird, usually in the albumen. In that same document the agency cited an estimate, based on 1991 to 1995 data, that of about 47,000 million shell eggs consumed each year as table eggs in the US, 2.3 million were SE-positive, around one in every 20,000. It is a low frequency, but no amount of shell washing addresses this route.
Horizontal or shell transmission
The second route starts outside: feces, dust, nests, equipment, packaging and hands. A 2025 review by the USDA Agricultural Research Service (Bermudez-Aguirre and colleagues) describes how bacteria can cross the layers of the egg from the surface, passing through the cuticle, the pores and the shell membranes, until they reach the contents. The cuticle is the first barrier; as the hen ages, the microbial load and the porosity of the shell increase, and cracks are entry points. The review notes that penetration and growth of Salmonella are reduced at refrigeration temperature, and that one study showed washing removes bacteria from the surface but not from the pores. Some studies cited in that review isolated mainly S. Enteritidis in the contents and S. Typhimurium on the shell, attributed to cross-contamination.
To wash or not to wash: two answers to the same problem
European Union: the intact shell as a barrier
Delegated Regulation (EU) 2023/2465, which replaced Regulation (EC) 589/2008, explains in its recitals that, as a general rule, eggs should not be washed or cleaned because these practices can damage the shell, which is an effective barrier against bacterial entry. It points in particular to damage to the cuticle, which can favor contamination and moisture loss, especially if subsequent drying and storage are not optimal. Article 4 turns this into concrete rules:
- Class A eggs may not be washed or cleaned, either before or after grading.
- They may not undergo preservation treatment or be chilled in premises artificially kept below 5 °C, except during transport of up to 24 hours or at retail for a maximum of 72 hours.
- Member States that on 1 June 2003 already authorized washing in packing centres may keep that authorization if national guidelines are followed; those eggs are labelled as "washed eggs" and sold only in those countries.
The same regulation acknowledges that some Member States wash eggs with good results under prior authorization and controlled conditions, and cites a 2005 EFSA opinion according to which washing can be acceptable from a hygiene standpoint if, among other measures, a code of practice is drawn up.
United States: wash, sanitize and chill
In the US, table eggs are washed. For plants under the USDA grading program, 7 CFR 56.76 requires potable water at 32.2 °C (90 °F) or higher and at least 6.7 °C (20 °F) warmer than the internal temperature of the eggs. It prohibits eggs from being immersed or left soaking, requires a spray rinse with a sanitizer of 100 to 200 ppm available chlorine (or equivalent), and requires eggs to be packed reasonably dry. Because the cuticle is lost, the cold chain becomes mandatory: 21 CFR 115.50 requires eggs to be stored and displayed at retail at 7.2 °C (45 °F) or below.
Each model is consistent with its own design: the EU protects the cuticle; the US cleans the surface and compensates with continuous refrigeration. What fails is washing without proper drying and chilling.
The FDA Egg Safety Rule (21 CFR 118)
Published in July 2009, the rule applies to producers with 3,000 or more laying hens on a farm who do not sell all their eggs directly to consumers; if all eggs receive a treatment, only the refrigeration and recordkeeping requirements apply. SE prevention measures include:
- Pullets monitored for SE, with environmental testing at 14-16 weeks.
- Biosecurity and pests. Limiting visitors, preventing wild birds and other animals from entering, and monitoring rodents and flies.
- Cleaning and disinfection of the poultry house after a positive environmental result.
- Refrigeration. Holding and transporting eggs at 7.2 °C (45 °F) or below starting 36 hours after laying.
Environmental sampling of each poultry house is done when the hens are 40 to 45 weeks old, and again 4 to 6 weeks after each molt. If the environment tests positive, the plan must be reviewed and egg testing must begin, unless the eggs are diverted to treatment: four tests at two-week intervals, each with a minimum of 1,000 intact eggs representative of one day's production, with the first result within 10 days. If an egg test is positive, all eggs from that flock are diverted to treatment, defined as a process that achieves at least a 5-log reduction of SE, or processing into egg products. The method for eggs is chapter 5 of the Bacteriological Analytical Manual (BAM) or one equivalent in accuracy, precision and sensitivity.
Liquid egg products: pasteurization under FSIS inspection
When eggs are broken to produce liquid, frozen or dried egg, they come under FSIS jurisdiction through the Egg Products Inspection Act. Breaking pools the contents of many eggs. The FSIS 2012-2013 baseline illustrates this: raw liquid whole egg had Salmonella concentrations of one organism per 2 to 4 mL, and raw liquid egg white, one per 2 to 8 mL.
9 CFR 590.570 set out a table of times and temperatures. For example: whole egg at 60 °C (140 °F) and yolk at 61.1 °C (142 °F), both for 3.5 minutes; egg white without additives at 56.7 °C (134 °F) for 3.5 minutes. The October 2020 final rule replaced it, with staggered deadlines through October 2022, with a performance standard: pasteurized egg products must be edible without additional preparation to achieve food safety. The rule also required HACCP and Sanitation SOPs in plants. FSIS recognizes a minimum 5-log reduction of Salmonella as a safe harbor, and warned that the old time-temperature combination for egg white might not achieve it, so it accepts it only under specific conditions.
To verify the standard, FSIS samples pasteurized egg products and tests them for Salmonella spp. and Listeria monocytogenes. In pasteurized egg white, Salmonella prevalence in its sampling fell from 0.61 % (1995-1999) to 0.19 % (2013-2018). Even so, the safety of the pasteurized product depends as much on the heat treatment as on what happens afterwards, in tanks, fillers and packaging.
What Regulation (EC) 2073/2005 requires for egg products
The European regulation has three relevant rows, each with a different logic:
- Row 1.14, egg products (food safety criterion). Salmonella not detected in 25 g, with n = 5 and c = 0, in products placed on the market during their shelf life. It excludes products whose manufacturing process or composition eliminates the risk. Reference method: EN ISO 6579-1.
- Row 1.15, ready-to-eat foods containing raw egg (food safety criterion). Salmonella not detected in 25 g or mL, n = 5, c = 0, during shelf life, with the same exclusion. This covers mayonnaise, sauces or desserts made with untreated egg.
- Row 2.3.1, egg products (process hygiene criterion). Enterobacteriaceae with n = 5, c = 2, m = 10 CFU/g or mL and M = 100 CFU/g or mL, at the end of the manufacturing process, by EN ISO 21528-2. If the result is unsatisfactory, the regulation calls for checking the efficiency of the heat treatment and the prevention of recontamination.
Salmonella answers whether the product is safe; Enterobacteriaceae, whether the pasteurizer worked and whether there was subsequent recontamination. What this group indicates is explained in aerobic mesophiles and Enterobacteriaceae, and how to read n, c, m and M in attributes sampling plans. In the 2024 EU data, 0.31 % of 12,327 units of eggs and egg products tested positive for Salmonella: a low positivity in the product that contrasts with the weight of eggs in outbreaks.
In primary production, Regulation (EC) 2160/2003 is the framework for reduction targets. For laying hens the target is 2 % of flocks positive for the target serovars (S. Enteritidis and S. Typhimurium, including its monophasic variant). In 2024 the prevalence in adult flocks was 1.6 % for those serovars, and seven Member States did not meet the target.
How testing is done: culture, PCR and confirmation
EN ISO 6579-1 remains the reference method for rows 1.14 and 1.15, and EN ISO 21528-2 for the Enterobacteriaceae count in row 2.3.1. Alternative methods, including real-time PCR on the enrichment broth, are acceptable in the EU if they are validated against the reference method according to EN ISO 16140-2, as explained in validation and verification of microbiological methods.
Two practical caveats. A genus-level PCR answers "Salmonella spp.", which is what rows 1.14 and 1.15 ask for; but the Egg Safety Rule focuses on S. Enteritidis, so a genus-level positive requires isolation and serotyping. And every PCR positive is presumptive until confirmed (see presumptive vs. confirmed result). For the Enterobacteriaceae criterion, on the other hand, the regulation requires a count (CFU/g), which a qualitative PCR does not replace.
In the breaking and pasteurization plant, environmental monitoring focuses on the area downstream of the heat treatment, with the same logic as in other processing plants (see environmental monitoring in food plants).
Which TAAG kits relate to this matrix
TAAG kits detect Salmonella at genus level: none distinguishes S. Enteritidis from other serovars. Among those with the broadest declared scope are Specio 1.1 Salmonella spp. (V-SF31, real-time PCR with melting curve), with a declared scope covering foods, beverages and living and inert surfaces, and Ampliora 2.8 Listeria spp. and Salmonella spp. (V-SF44, probe-based real-time PCR), with the same general scope and a declared sensitivity of 1 CFU/25 g in foods. For broken-out egg, Elevia 1.1 Salmonella spp. (V-PAT04, RT-qPCR with AiGOR) includes pasteurized liquid eggs among its validated matrices, with a declared sensitivity of 1 CFU/375 g in foods, and Specio 4.1 (V-SF95) lists pasteurized liquid egg and pasteurized liquid yolk. For the plant environment, Elevia 2.9 Salmonella spp. and Enterobacteria (V-PAT06, RT-qPCR with AiGOR) is validated on stainless steel surfaces (1 CFU/sample for Salmonella, 10 CFU/sample for Enterobacteriaceae), qualitatively. Shell eggs, other egg products and farm samples are not among the declared matrices: before using these kits on them, it is advisable to confirm the scope with TAAG and to verify the method in your own laboratory.
Conclusion
Eggs combine two contamination routes that call for different controls: the vertical route is fought on the farm, with flock monitoring, biosecurity and pest control, and the horizontal route through shell handling and temperature. The EU and the US reach opposite solutions on washing, but both are consistent as long as their drying and chilling conditions are respected. In egg products, pasteurization validated for at least a 5-log reduction and the prevention of recontamination are the core, and the Enterobacteriaceae criterion of Regulation 2073/2005 is the most direct way to verify both. The laboratory adds value when each analysis answers the right question: Salmonella spp. or S. Enteritidis, presence or count, screening or confirmation.
About TAAG
Ask TAAG about the scope of Elevia 1.1 Salmonella spp., validated in pasteurized liquid eggs, Specio 1.1 Salmonella spp. and Elevia 2.9 Salmonella spp. and Enterobacteria for your egg, egg product and plant environment samples.
Frequently asked questions
How does Salmonella get inside an egg?
Through two routes. In the vertical route, S. Enteritidis infects the hen's ovaries or oviduct and contaminates the contents, usually the albumen, before the shell is formed. In the horizontal route, bacteria on the surface cross the cuticle, the pores and the membranes, which is favored by cracks, moisture and temperature.
Why are eggs not washed in the European Union while they are in the US?
The EU protects the cuticle, which it considers an effective barrier against bacterial entry, and prohibits washing Class A eggs except under national authorizations predating 2003. The US washes and sanitizes the shell with water warmer than the egg and compensates for the loss of the cuticle with mandatory refrigeration at 7.2 °C or below. Each system is consistent with its own design.
What does the FDA Egg Safety Rule require?
It applies to farms with 3,000 or more laying hens and requires an S. Enteritidis prevention plan: monitored pullets, biosecurity, rodent and fly control, cleaning after positives and refrigeration starting 36 hours after laying. If environmental sampling of the poultry house is positive, eggs are tested (four tests of at least 1,000 eggs) or diverted to treatment.
What microbiological criteria does Regulation 2073/2005 apply to egg products?
A food safety criterion of Salmonella not detected in 25 g (n = 5, c = 0) during shelf life, which also applies to ready-to-eat foods containing raw egg. In addition, a process hygiene criterion for Enterobacteriaceae at the end of manufacturing, with m = 10 and M = 100 CFU/g and c = 2, which serves to verify pasteurization and recontamination.
Is PCR suitable for testing Salmonella in eggs and egg products?
It works as a rapid screening on the enrichment broth and, in the EU, as an alternative to EN ISO 6579-1 if it is validated according to EN ISO 16140-2 for that food category. A positive is presumptive until confirmed, and if the program requires identifying S. Enteritidis, isolation and serotyping are needed. For the Enterobacteriaceae count, a quantitative method is required.