Detection of Salmonella from raw food samples using Dynabeads® anti-Salmonella and a conventional reference method

Abstract

A Dynal core method has been established using Dynabeads anti-Salmonella to detect Salmonella from all categories of food samples. The protocol consists of the standard pre-enrichment of samples in buffered peptone water followed by immunomagnetic separation and subsequent selective enrichment of the bead-bacteria complexes in Rappaport-Vassiliadis Soya Peptone broth before plating onto Salmonella selective media. This modified IMS cultural method is intended to replace or augment traditional cultural methods used for Salmonella detection due to its specificity and increased sensitivity. The optional direct plating of bead-bacteria complexes onto solid media using a swab-streak technique is suitable for processed foods or samples known to have a history of very low resident flora. In an evaluation using 100 naturally contaminated samples, this IMS core method detected 39 of the 44 positive samples detected by all the methods combined, compared to 31 detected by the conventional ISO 6579 reference method. Furthermore, in ten different food matrices inoculated with low levels (1-5 cells/25 g) of twenty Salmonella serovariants, frozen for one month before being examined, the IMS core method, showed a 90% concordance with the ISO method and isolated two more Salmonella positive samples than the conventional ISO method.