Cross-sectional studyindependent cross-checkabstract checked I-EGG-132 standard review
Chile: Salmonella found only in cage-free eggs
Prevalence of Salmonella in Eggs from Conventional and Cage-Free Egg Production Systems and the Role of Consumers in Reducing Household Contamination.
Overview
Solís D et al.. Foods 2023 · PMID 38231772 · DOI 10.3390/foods12234300
Salmonella Enteritidis was found in 2 of 186 cage-free egg samples and none of 240 conventional samples.
Does the study support the specific claim? No · Methodological quality: moderate
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Compare Salmonella in eggs by production system.
- How was the study done?
Egg sampling and sequencing.
- How many people, animals or samples were studied?
426 samples.
- What was actually found?
Only cage-free eggs positive (1.1%).
- How large was the observed effect?
1.1% vs 0%.
- What do the results mean in everyday life?
Cage-free or free-range eggs also need safe handling and cooking.
- What are the study's limitations?
Very few positives.
- What does it say about Elawady's specific claim?
Contradicts the simple cage rule.
- Do the results apply to Germany and Europe?
Moderate.
- What can explicitly not be concluded from this study?
It cannot show which system is safer overall.
Scientific in-depth review
1. Full reference
- Authors
- Solís D et al.
- Journal
- Foods
- Year
- 2023
- Identifier
- PMID 38231772 DOI 10.3390/foods12234300
- Verification
- verified – PubMed efetch 2026-10-26; Crossref works API 2026-10-26
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
Funded by Sinergia Animal (animal-welfare organisation) per PubMed grant list; authors declare no conflict of interest.
2. Research question
How common is Salmonella in eggs from conventional vs alternative (cage-free) production systems?
3. Study design and population
- Study design
- Cross-sectional study – Cross-sectional egg sampling with whole-genome sequencing plus consumer survey
- Population
Eggs from conventional and alternative systems
- Country
Chile (University of Chile study)
- Period
not stated in abstract
- Sample size
426 egg samples (240 conventional, 186 alternative)
- Inclusion and exclusion criteria
not detailed in abstract
4. Methods and endpoints
- Exposure / intervention
Alternative (cage-free) systems
- Comparator
Conventional (cage) systems
- Endpoints
Salmonella detection; serotype; resistance genes
- Statistical methods
Proportions
5. Actual results
- Results
Salmonella Enteritidis detected only in eggs from alternative (cage-free) systems: 1.1% (2/186); none in 240 conventional samples. Both isolates resistant to nalidixic acid.
- Absolute risks
not reported
- Authors' conclusion
Consumers know about food safety but many still use risky practices; Salmonella was detected only in alternative-system eggs.
6. Strengths
- Direct egg sampling of both systems
- Genomic confirmation
7. Weaknesses
- Very few positives (2)
- Single country
8. Risk of bias
- Orienting tool
- none applicable
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- some concerns
- Rationale
Low event count.
9. Assessment of the statistical interpretation
2/186 vs 0/240 is not a statistically robust difference; it shows cage-free eggs are not Salmonella-free.
10. Relevance to the specific claim
In this sample the only Salmonella Enteritidis came from cage-free eggs, contradicting a universal 'cages = more Salmonella' rule at the level of eggs on sale.
11. Independent contrary findings
UAE retail data showed the opposite (I-EGG-124).
12. Transferability to Germany and Europe
Latin American setting.
13. Overall methodological judgement
Small but direct counter-example.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | low |
| Directness | direct |
| Reproducibility | unknown |
| Consistency with the overall evidence | inconsistent |
| Regional transferability | moderate |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Larger comparative retail studies.
15. Linked fact checks
- Salmonella is far more common in caged egg production than in cage-free systems (44% vs 3.2%). – Studies contradicting or limiting the claim