Chicken Meal Detection Salmonella : VIDAS vs API 20E vs SN 0170-92
Choline Chloride for Root & Tuber Expansion
October 9, 2026
1. Research Scope and Analytical Objective
This study employs three distinct detection methods — VIDAS, API 20E, and SN 0170-92 — to examine a blind sample provided in the CNCA proficiency-testing programme for common pathogenic bacteria in chicken meal. The strengths and weaknesses of each method for the detection of Salmonella are summarised and compared. Salmonella is transmitted mainly through the digestive tract of animals and can cause typhoid and paratyphoid fever (collectively known as enteric fever), food poisoning, septicaemia, and chronic enteritis. Because Salmonella is widespread in nature and poses a substantial threat to human health, the hygiene regulations of countries worldwide generally stipulate that Salmonella must not be detected in chicken meal.
At present, the commonly used detection methods include conventional biochemical test methods such as the national standard method (GB) and the import and export commodity inspection industry standard (SN); the VIDAS method, which relies on enzyme-linked immunofluorescence technology; and molecular biology methods such as PCR. Each method has its own advantages and disadvantages. In 2006, this laboratory participated in the CNCA proficiency test “Common Pathogenic Bacteria in Chicken Meal (CNCA-06-02)” and detected one Salmonella isolate using three different methods: VIDAS, SN 0170-92, and API 20E. The present report documents that work in full.
The technical dossier is structured as a structured data reference rather than a narrative article. It uses a high density of standard tables to present instrument configurations, reagent sources, procedural steps, biochemical reaction profiles, time-consumption breakdowns, accuracy assessments, and method-selection guidance. This format is designed to support rapid indexing, featured-snippet extraction, and direct laboratory bench use.
2. Key Performance Indicators at a Glance
Consolidated headline parameters extracted from the comparative detection programme.
3. Instrumentation and Reagent Sources
Each of the three detection routes relies on a distinct instrument and reagent ecosystem. The table below documents the manufacturer and supplier for every critical consumable, so that the method can be reproduced without ambiguity.
4. Testing Basis and Reference Standards
The SN method follows SN 0170-92. The VIDAS and API 20E procedures were executed according to the manufacturer’s prescribed operation protocols. The table below links each method to its governing document and specifies the level of procedural freedom allowed.
| Method | Governing Document | Procedure Control | Standard Status |
|---|---|---|---|
| SN 0170-92 | SN 0170-92, export chicken meal Salmonella inspection method | Prescribed in full by the standard | Industry reference method |
| VIDAS | Manufacturer’s validated procedure | Instrument-driven, software-controlled | FDA-recognised rapid screening method |
| API 20E | Manufacturer’s validated procedure | Manual strip inoculation, software readout | Miniaturised conventional biochemical method |
| Capacity test | CNCA-06-02 proficiency-testing scheme | Blind sample distributed by CNCA | Inter-laboratory comparison |
5. SN 0170-92 Detection Workflow
The SN 0170-92 procedure is the most comprehensive of the three routes. It proceeds from pre-enrichment through selective enrichment, isolation on differential media, screening tests, biochemical confirmation, and serological typing. Each stage is separated in time and requires a distinct set of media and reagents.
| Stage | Operation | Media / Reagent | Conditions | Duration |
|---|---|---|---|---|
| 1 | Pre-enrichment | Buffered peptone water (BP) | 37 °C | 24 h |
| 2 | Selective enrichment | Tetrathionate brilliant green broth (TTB) | 42 °C | 6–8 h |
| 3 | Isolation | Bismuth sulfite agar; DCLS agar | 37 °C | 24 ± 2 h |
| 4 | Screening tests | Triple sugar iron (TSI) agar | 37 °C | 24 h |
| 5 | Biochemical confirmation | Lysine decarboxylase, urease, V-P, KCN, indole, malonate, dulcitol | 37 °C | 24–48 h |
| 6 | Serological confirmation | “O” factor antiserum | Slide agglutination at room temperature | Minutes |
6. VIDAS Detection Workflow
The VIDAS route compresses the detection chain into four principal steps: pre-enrichment, selective enrichment, post-enrichment in M broth, and automated immunoassay. No isolation plate and no manual biochemical strip are required, which is the key reason for its short elapsed time. A 1 mL portion of the M broth is heat-treated at 100 °C for 15 min, and 0.5 mL of the treated culture is loaded into the reagent strip for instrument reading.
| Step | Operation | Medium / Treatment | Conditions | Duration |
|---|---|---|---|---|
| 1 | Pre-enrichment | 25 g sample in 225 mL buffered peptone water | 37 °C | 24 h |
| 2 | Selective enrichment | 10 mL into 100 mL TTB | 42 °C | 6–8 h |
| 3 | Post-enrichment | 1 mL into 10 mL M broth | 42 °C | 18 h |
| 4 | Sample treatment | 1 mL M broth heated in water bath | 100 °C, 15 min | 15 min |
| 5 | Instrument assay | 0.5 mL into VIDAS SLM reagent strip | Automated mini-VIDAS | ≈1 h |
| 6 | Result output | Printed report from instrument | Automatic interpretation | Immediate |
7. API 20E Detection Workflow
The API 20E route preserves the conventional enrichment and isolation sequence but replaces the individual biochemical tubes with a single 20-well reagent strip. A suspicious colony is picked from the isolation plate, suspended, and inoculated into the micro-tubes. After incubation and addition of auxiliary reagents, the positive/negative pattern is converted into a numerical profile and submitted to the API LAB software for identification.
| Step | Operation | Medium / Reagent | Conditions | Duration |
|---|---|---|---|---|
| 1 | Pre-enrichment and selective enrichment | BP followed by TTB | 37 °C then 42 °C | 24 h + 6–8 h |
| 2 | Isolation culture | Bismuth sulfite agar and DCLS agar | 37 °C | 24 ± 2 h |
| 3 | Colony suspension | Suspicious single colony | Sterile saline | Preparation |
| 4 | API 20E strip inoculation | 20 micro-tubes on single strip | 37 °C | 24 ± 2 h |
| 5 | Reagent addition and reading | Auxiliary reagents | Manual colour interpretation | Minutes |
| 6 | API LAB software analysis | Numerical profile | Database matching | Immediate |
8. Comparative Detection Results
All three methods returned a positive Salmonella result for the blind sample. The differences lie in the taxonomic resolution achieved and in the supporting evidence required to reach that conclusion. SN 0170-92 and VIDAS identified the organism to species level, while API 20E additionally resolved the serotype as Salmonella Paratyphi A with a %ID of 99.5 and a T-value of 1.
9. API 20E Biochemical Reaction Profile
The sample was inoculated into the 20 micro-tubes of the API 20E strip. The table below records the observed positive (+) or negative (−) reaction for every test. This profile is the raw data from which the API LAB software computed the identification.
| ONPG | ADH | LDC | ODC | CIT | H2S | URE | TDA | IND | VP |
|---|---|---|---|---|---|---|---|---|---|
| − | − | − | + | − | − | − | − | − | − |
| GEL | GLU | MAN | INO | SOR | RHA | SAC | MEL | AMY | ARA | OX |
|---|---|---|---|---|---|---|---|---|---|---|
| − | + | + | − | + | + | − | + | − | + | − |
Software output: API LAB identified the profile as Salmonella Paratyphi A, with %ID = 99.5 and T-value = 1, rated as an excellent identification.
10. Accuracy and Taxonomic Resolution Comparison
SN 0170-92 and VIDAS both returned a Salmonella positive result at species level. API 20E returned Salmonella Paratyphi A, identifying the organism to serotype. The following table compares the resolution, evidence chain, and confirmation burden of each method.
| Criterion | SN 0170-92 | VIDAS | API 20E |
|---|---|---|---|
| Final call | Salmonella positive | Salmonella positive | Salmonella Paratyphi A |
| Taxonomic depth | Species | Species (screening) | Serotype |
| Identification confidence | High (reference method) | High for screen | %ID 99.5; T = 1 |
| Biochemical evidence | Multiple individual tubes | None (immunological) | 20 consolidated reactions |
| Serological evidence | Yes (“O” antiserum) | No | No (software inference) |
| Confirmation burden | Self-contained | Positive requires conventional confirmation | Self-contained |
| Regulatory standing | Reference method for disputes | FDA-recognised screening | Miniaturised conventional |
11. Time Consumption Breakdown
The total elapsed time is the decisive operational parameter when selecting a detection method. SN 0170-92 requires approximately 100 h, API 20E approximately 73 h, and VIDAS approximately 49 h 45 min. When the common enrichment steps, which consume roughly 48 h in all three methods, are excluded, the difference becomes even more pronounced: SN 0170-92 requires about 73 h, API 20E about 49 h, and VIDAS only about 1 h (or about 19 h if the post-enrichment step is included).
12. Procedural Step Comparison
The three methods share the initial enrichment sequence but diverge sharply thereafter. SN 0170-92 proceeds through isolation culture, screening tests, biochemical tests, and serological testing. API 20E proceeds through isolation culture, the API 20E reagent strip, and API LAB software analysis. VIDAS requires only enrichment, a 15-minute heat treatment, and instrument loading.
| Process Stage | SN 0170-92 | API 20E | VIDAS |
|---|---|---|---|
| Enrichment culture | ✓ | ✓ | ✓ |
| Isolation culture | ✓ | ✓ | — |
| Screening tests | ✓ | — | — |
| Biochemical tests | ✓ (individual tubes) | ✓ (20-well strip) | — |
| Serological tests | ✓ | — | — |
| Instrument reading | — | — | ✓ (mini-VIDAS) |
| Software analysis | — | ✓ (API LAB) | ✓ (onboard) |
13. Underlying Technology Principle Comparison
The SN 0170-92 method depends on the phenotypic expression of the organism in culture media and on antigen–antibody agglutination. API 20E also depends on phenotype, but miniaturises the biochemical reactions and delegates interpretation to a database. VIDAS uses an enzyme-linked fluorescent assay (ELFA) in which a fluorescent compound bound to a highly specific monoclonal antibody reacts with Salmonella antigen; the resulting fluorescent substance is detected by the instrument, enabling rapid screening.
| Method | Detection Principle | Molecular Target | Readout Mode |
|---|---|---|---|
| SN 0170-92 | Conventional culture, biochemical reactions, seroagglutination | Metabolic enzymes and O antigens | Visual colour / agglutination |
| API 20E | Miniaturised biochemical reactions on one strip | 20 enzyme / fermentation pathways | Visual colour change plus software database |
| VIDAS | Enzyme-linked fluorescent assay (ELFA) | Salmonella antigen | Instrument fluorescence signal |
| Automation level | Manual | Manual inoculation, automated interpretation | Fully automated assay |
| Regulatory recognition | Internationally accepted reference method | Widely used conventional method | FDA-recognised rapid screen |
14. Advantages and Disadvantages of Each Method
Each of the three methods occupies a distinct position on the trade-off curve between speed, cost, resolution, and regulatory acceptance. The following table consolidates the strengths and limitations observed in this comparative study.
15. Method Selection Guidance by Application Scenario
No single method is optimal for every laboratory context. The selection matrix below maps the three methods to common operational scenarios, so that a laboratory can choose the most appropriate route according to its throughput, budget, and regulatory environment.
| Scenario | Recommended Method | Rationale |
|---|---|---|
| High-throughput screening | VIDAS | Shortest turnaround, automated readout |
| Serotype-level identification required | API 20E | Direct typing with %ID 99.5 |
| Regulatory dispute or confirmatory testing | SN 0170-92 | Internationally recognised reference method |
| Limited equipment budget | SN 0170-92 | No expensive instrument required |
| Rapid positive confirmation of VIDAS screen | API 20E or SN 0170-92 | Conventional confirmation of presumptive result |
| Balanced speed and resolution | API 20E | Intermediate time with high taxonomic depth |
16. Critical Parameter Summary Table
The table below consolidates every quantitative parameter reported in the study into a single lookup reference. It is intended for direct insertion into laboratory standard operating procedures and method-validation dossiers.
| Parameter | SN 0170-92 | API 20E | VIDAS |
|---|---|---|---|
| Sample size | 25 g | 25 g | 25 g |
| Pre-enrichment volume | 225 mL BP | 225 mL BP | 225 mL BP |
| Selective enrichment | 10 mL into 100 mL TTB | 10 mL into 100 mL TTB | 10 mL into 100 mL TTB |
| Post-enrichment | — | — | 1 mL into 10 mL M broth |
| Heat treatment | — | — | 100 °C, 15 min |
| Isolation media | Bismuth sulfite; DCLS | Bismuth sulfite; DCLS | None |
| Biochemical platform | Individual tubes | API 20E strip | None |
| Serology | “O” antiserum | Not required | Not required |
| Instrument | None | API LAB software | mini-VIDAS |
| Total time | ≈100 h | ≈73 h | ≈49 h 45 min |
| Identification level | Species | Serotype | Species (screen) |
17. Discussion Synthesis
The current Chinese import and export inspection and quarantine industry standard for Salmonella (SN 0170-92) relies on biochemical reactions and serological reactions to identify and confirm Salmonella. It has a long detection cycle, a complex biochemical test procedure, and requires a large number of reagents. API 20E essentially continues the traditional method but achieves miniaturisation and consolidation of the biochemical tests: 20 biochemical reactions are concentrated on a single strip, and all biochemical tests are completed in one operation. VIDAS adopts modern enzyme-linked immunofluorescence technology (ELFA). It uses a fluorescent compound bound to an antibody; when a highly specific fluorescent-labelled monoclonal antibody reacts with Salmonella antigen, the resulting fluorescent substance can be detected by the instrument, thereby achieving rapid screening for Salmonella. The VIDAS method has received US FDA recognition.
18. Structured Data Snapshot — Complete Specification Reference
| Study identification | CNCA-06-02 proficiency test, chicken meal, common pathogenic bacteria |
| Methods compared | VIDAS, API 20E, SN 0170-92 |
| Sample result | One positive Salmonella isolate, typed as S. Paratyphi A |
| SN 0170-92 time | ≈100 h total; ≈73 h excluding enrichment |
| API 20E time | ≈73 h total; ≈49 h excluding enrichment |
| VIDAS time | ≈49 h 45 min total; ≈1 h excluding enrichment (≈19 h with post-enrichment) |
| API 20E identification | %ID = 99.5, T-value = 1, excellent identification |
| Key VIDAS limitation | Reported false positives; positive results require conventional confirmation |
| Key SN 0170-92 strength | Internationally accepted reference method; basis for dispute resolution |
| Key API 20E strength | Consolidated 20-reaction biochemical strip; direct identification to serotype |
19. Final Recommendations from the Comparative Study
The findings of this comparative study support a layered laboratory strategy rather than the exclusive adoption of a single method. The recommended operational model combines rapid screening with confirmatory reference testing and targeted typing.
| Priority | Recommendation | Justification |
|---|---|---|
| HIGH | Use VIDAS as the primary screening tool for high-volume samples | Shortest turnaround, simplest workflow, FDA recognition |
| HIGH | Confirm all VIDAS-positive results by SN 0170-92 or API 20E | AOAC reports false positives; conventional confirmation is required |
| MEDIUM | Use API 20E when serotype-level identification is required | Direct typing with %ID 99.5 and T-value 1 |
| MEDIUM | Retain SN 0170-92 as the dispute-resolution reference method | Internationally accepted baseline for Salmonella identification |
| LOW | Document the method-selection rationale in the laboratory quality manual | Supports accreditation audits and client transparency |
| LOW | Track VIDAS false-positive rates as a routine quality indicator | Enables continuous performance monitoring of the screening step |
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