Evaluation of rapid «Salmonella» immunoassays and characterization of bacterial isolates that cause false-negative and false-positive in the tests
Notice bibliographique
Résumé
Salmonella spp. is a widely distributed Gram-negative foodborne pathogen that is a major cause of foodborne outbreaks in North America. The Public Health Agency of Canada (PHAC) estimates that approximately 88,000 Canadians are affected by foodborne Salmonellosis annually. In recent years, contaminated fresh produce has emerged as an important source of salmonellosis. Standardized culture methods for Salmonella spp. are considered as the "gold standard" in food diagnostics and are still in use today; however, they are laborious, time-consuming and must be confirmed by secondary biochemical tests. Immunoassays are the most commonly used rapid methods for the detection of Salmonella in food, and presumptive results are available within 8 to 24 hours. However, a common issue observed using immunoassays to test fresh produce for the presence of Salmonella, is a high percentage of false-positive test results due to the misidentification of closely related, non-Salmonella bacteria such as Citrobacter spp., Hafnia spp. and Proteus spp. In addition, there is also the chance of false-negative test results, due to high variation in surface antigens of Salmonella enterica. In this study, two commercially available immunoassays, the VIDAS UP Salmonella Phage Technology (SPT) Assay (BioMérieux, Saint-Laurent, Quebec, Canada, Inc.) and an antibody-based lateral-flow test, the Reveal 2.0 Salmonella Assay (Neogen Corporation, Lansing, Michigan, United States) were evaluated for their accuracy in detecting Salmonella. VIDAS UP Salmonella (SPT) assay correctly identified 52/54 (96.3%) of the Salmonella isolates that were tested. The Reveal 2.0 Salmonella Assay identified 43/54 (79.63%) of the Salmonella isolates correctly. However, both assays failed to identify one isolate each of Salmonella enterica serovars Hull and Duesseldorf. Several VIDAS UP Salmonella (SPT) enrichment samples were obtained from a fresh produce grower. These enrichments had previously tested presumptive positive for Salmonella, however, confirmatory tests did not indicate the presence of Salmonella. The enrichments were analyzed in order to obtain pure isolates of bacteria from the enrichment mixture that were responsible for the false positive test results. Three bacterial isolates that caused false-positive VIDAS UP Salmonella (SPT) reactions were isolated and subjected to whole genome sequencing and bioinformatic analysis. Blast analysis of the three false-positive isolates identified Citrobacter amalonaticus as the likeliest organism. The two isolates (one each) of S. Hull and S. Duesseldorf that produced false-negative results were analyzed in order to identify surface exposed components that are used as diagnostic targets in Salmonella immunoassays. Analysis of S. Duesseldorf showed that the flagella genes fljB and fliC differed significantly from other Salmonella isolates that tested positive, and the three C.amalonaticus isolates that caused false-positive test results. Analysis of the S. Hull genome identified a gene encoding a putative repression of phase I flagellin, which was located on a cryptic incomplete prophage. Both of these observations are likely responses for the lack of complete flagella on the surface of the S. Duesseldorf and S. Hull isolates, which may be responsible for the false-negative test results. The results of this work have identified the potential basis for false-positive and false-negative test results in rapid Salmonella immunoassays. The development of more selective immunoassays based on more specific monoclonal antibodies, identification of new antigens that are more specific to Salmonella and development of more selective enrichment media will lead to improved fresh produce testing and enhanced food safety in Canada.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,006 | 0,007 |
| Méta-épidémiologie (sens strict) | 0,001 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,001 |
| Bibliométrie | 0,002 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,001 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,001 | 0,001 |
| Intégrité de la recherche | 0,001 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,001 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».