**7. Conclusion**

406 Salmonella – A Dangerous Foodborne Pathogen

antibodies. All of the assay steps are performed automatically by the VIDAS instrument. For the detection of *Salmonella by* VIDAS SLM, the sample is inoculated into lactose broth and incubated for 18 h at 37°C (non-selective pre-enrichment). Subsequently, 0.1 ml of this medium is inoculated into Rappaport–Vassiliadis broth and 1 ml into tetrathionate broth, and then incubated for 8 h at 42°C and 8 h at 37°C, respectively. Then, 1 ml of each broth is inoculated separately into 10 ml of M-broth and incubated at 42°C for 18 h. Finally, 1 ml of each broth is placed in a tube, which is heated for 15 min at 100°C. Following preenrichment, immuno-concentration, and postenrichment of test portions, an aliquot of the boiled test suspension is placed into the reagent strip and is cycled in and out of the SPR for a specific length of time. *Salmonella* antigens, if present, bind to the monoclonal antibodies coating the interior of the SPR. All other unbound material is washed away. Antibodies conjugated with alkaline phosphatase are cycled in and out of the SPR, binding to any *Salmonella* antigen bound to the SPR wall. The final wash step removes unbound conjugate. The substrate, 4-methyl umbelliferyl phosphate, is converted by the enzyme on SPR wall to

The intensity of fluorescence is measured by the optical scanner in VIDAS. The fluorescence intensity is measured twice at 450 nm. The first result is related to the background, the second it the value after incubation of the substrate with enzyme. Based on that, the apparatus calculates the result of the test and interprets it as a positive or negative one. RFV (Relative Fluorescence Value) is calculated as the difference between the sample and background fluorescences. The printed report contains the RFV value of the sample, RFV value of the standard, and test value (TV), which is a quotient of the sample value and standard value. A result was interpreted by the apparatus as positive, if TV ≥ 0.23, while as negative if TV ≤ 0.23. Results are interpreted after the test values and control are compared to thresholds stored in the computer. A positive result requires confirmation with classical culture methods, that is streak plating on two plates with selection growth medium. For confirmation, previously prepared and stored under cold conditions broth culture of the

Based on the comparative studies with the standard plate method, it can be concluded that the VIDAS system can be use to get fast results; however, because these results can be false positive then they have to be confirmed by culture method (Yeh et al., 2002; Zadernowska et

Problems with detection of some *Salmonella* spp. serotypes were observed during detection by the immunoenzymatic method. This may be caused by weak binding of antibodies, which is confirmed by results obtained by other authors. Vitek Immunodiagnostic Assay System (VIDAS, BioMérieux) are currently used in the meat and poultry processing industries (Maciorowski et al., 2006). Several validation studies have been reported that the detection rate of VIDAS systems were comparable to that of culture method (Yeh et al.,

**VIDAS Salmonella Xpress** (VIDAS SLMX) is most rapid method for the detection of *Salmonella than VIDAS SLM*. The results are obtained as little as 17 hours. The method has been simplified with a single enrichment in buffer peptone water and just one pipeting step. A broad incubation time of 16 to 24 hours simplifies the laboratory workflow, enabling all samples to be processed as they arrive during the day. This test is validated for raw beef and

**VIDAS UP Salmonella** is a new generation of assay based on **the latest technology**  available for pathogen screening: Phage recombinant protein. Bacteriophages are viruses

2002) and real-time PCR (Uyttendaele et al., 2003) for detecting of *Salmonella* in food.

veal meats (including frozen), not flavoured and pasteurized egg products.

the fluorescent product, 4-methyl umbelliferone.

investigated sample is used.

al., 2010; Walker et al., 2001)

Numerous and diverse alternative methods for microbial analysis of foods, as described above, exist (Bohaychuk et al., 2005; Wu, 2008) . They are currently brought to the market by various suppliers in a variety of formats as a result of recent developments, particularly in the field of biotechnology, microelectronics and related software development. Many of them have been proven to be equivalent to the "golden standard" reference methods with regard to the performance characteristics of the method.

Fig. 2. Detection of *Salmonella* spp. from food.

Detection of *Salmonella* spp. Presence in Food 409

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Fach, P., Micheau, P., Mazuet, C., Perelle, S., Popoff, M. (2009). Development of real-time

Fang, Q.; Brockmann, S.; Botzenhart, K., Wiedenmann, A. (2003). Improved detection of

Favrin, S.J., Jassim, S.A., Griffiths, M.W. (2003). Application of a novel immunomagnetic

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Glynn, B., Lahiff, S.,Wernecke, M., Barry, T., Smith, T.J., Maher, M. (2006). Current and

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International Standards Organization. ISO 6579 Microbiology of food and animal feeding stuffs - Horizontal method for detection of *Salmonella spp*. 6579:2002 Jasson, V.; Jacxsens, L., Luning P., Rajkovic, A., Uyttendaele, M. (2010). Alternative

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Due to an overload of alternative methods and/or formats on the market, food business operators or competent authority, for which microbial analysis of food is only a supporting tool in the assurance of food safety, have difficulties in deciding which method is best fit for their purpose in their particular context. (Jasson et al., 2010)

Evolution in alternative rapid methods, mainly immunological and molecular methods, focus on the combination of available techniques e.g. combination of immunocapture and PCR and/or by elaboration of new formats optimizing reading and registration software rather than introducing new principles of detection or enumeration.
