Detection of Salmonella in Food Matrices, from Conventional Methods to Recent Aptamer-Sensing Technologies

Abstract

Rapid detection of the foodborne pathogen Salmonella in food processing is of crucial importance to prevent food outbreaks and to ensure consumer safety. Detection and quantification of Salmonella species in food samples is routinely performed using conventional culture-based techniques, which are labor intensive, involve well-trained personnel, and are unsuitable for on-site and high-throughput analysis. To overcome these drawbacks, many research teams have developed alternative methods like biosensors, and more particularly aptasensors, were a nucleic acid is used as biorecognition element. The increasing interest in these devices is related to their high specificity, convenience, and relative rapid response. This review aims to present the advances made in these last years in the development of biosensors for the detection and the quantification of Salmonella, highlighting applications on meat from the chicken food chain.

Keywords: Salmonella; aptamers; biosensors; food matrices; standard methods.

Figure 1

Conventional methods used for food borne pathogenic bacteria detection.

Figure 2

International standard NF EN ISO 6579. This international standard is a horizontal method used for the detection of Salmonella, including S. Typhi and S. Paratyphi, in products intended for human consumption or animal feed and in environmental samples in the area of production and handling of food.

Figure 3

Comparison of the analytical time of the conventional methods versus the biosensors and the aptasensors for the detection of foodborne bacteria.

Figure 4

Synoptic representation and classification of biosensors.

Figure 5

Structure of the lateral flow assay system.

Figure 6

Synoptic representation of the SELEX method for DNA library. Three main stages constitute a general SELEX protocol, the incubation of the library with the target which is sometimes bound to a support, the separation of the oligonucleotides linked to the target from the unbound oligonucleotides from the library, and the amplification of the oligonucleotides linked to the target. For this representation, the primers are modified with a fluorochrome for the forward primer and with biotinylated magnetic beads. After the last stage, the amplified oligonucleotides (dsDNA) are denatured, in this representation, with the help of magnetic beads which are retained by a magnet, and therefore only the ssDNA tagged with the fluorochrome are used for the next round. The presence of the fluorochrome tracks the amounts of aptamers selected during the SELEX process. For RNA-SELEX, some additional steps are included first, i.e., an in vitro transcription to obtain an RNA library, and the reverse transcription of bound RNA molecules to obtain cDNA and its subsequent amplification.