Purpose: To evaluate the performance of a new Salmonella molecular detection method through comparison with a cultural method and an ELFA method for Thai vegetable matrices.
Methods: A total of 115 samples were tested: 35 samples were artificially contaminated with a low level of Salmonella (1.9-6.6 CFU/test portion); 30 samples were artificially contaminated with a medium level of Salmonella (31‑36 CFU/test portion); 50 samples were tested without artificial contamination. After a shared enrichment (125g test portion diluted 1:10 in BPW at 37+1°C for 18-24h), all samples were analyzed by three methods: (a) 3M™ Molecular Detection Assay (MDA) Salmonella (modified); (b) ELFA method and (C) ISO 6579. The modified 3M method involved a secondary RVS Broth enrichment incubated at 41.5+1°C for 22-24 hours. Presumptive positive molecular results were culturally and biochemically confirmed following ISO 6579 procedures.
Results: For the 115 samples tested, the 3M MDA Salmonella method showed 100% sensitivity, 97% accuracy, 90% specificity while the ELFA method showed 96% sensitivity, 97% accuracy, 100% specificity. No statistical difference between the 3M MDA Salmonella method and reference method can be detected using the McNemar test and the 3M MDA Salmonella method reported a relative detection level of 0-1.9 CFU/test portion.
Significance: The 3M™ MDA Salmonella offers sensitive and reliable results for the detection of Salmonella in 125g of artificially and naturally contaminated Thai vegetables and offers significant advantages for exporters of Thai vegetables, including faster time to results.