**1. Introduction**

412 Salmonella – A Dangerous Foodborne Pathogen

Zadernowska, A., Łaniewska-Trokenheim, Ł., Chajęcka,W. (2010) Detection of *Listeria* 

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*monocytogenes* and *Salmonella* sp. rods in fish and fish products using the mini

#### **1.1 Using molecular biological methods to identified** *Salmonella* **spp.**

As the industrialization had made food supply to exceed demand, more and more consumers were interested in 'Delicious food' than 'Good quality food' today and they ask for not only taste but also safety. Microbiological safety is one of the most critical factors for ensuring safe food supply. Fig 1. is a flow chart of traditional detection procedure for *Salmonella* spp., showing that it takes about one week. Therefore, a rapid screening method using PCR is the basis of most molecular diagnostic laboratories. As the field of molecular pathology becomes more accessible to practicing pathologists, a working knowledge of PCR techniques is necessary related to biological safety of food is very essential in food industry. *Salmonella* spp. are an important cause of food-borne infections throughout the world, and the availability of rapid and simple detection techniques is critical for the food industry.

Fig. 1. Traditional procedure for the detection of *Salmonella* spp. (ISO/CD draft standard 6575 revision 2000)

Studies on PCR-Based Rapid Detection Systems for Salmonella spp. 415

and TAMRA(6-Carboxy-Tetramethyl-Rhodamin) are most frequently used as reporter and quencher, respectively. This PCR is often referred to as 5' exonuclase-based, real-time PCR

Recently, Jung *et al*. (2010) developed a new highly sensitive and specific isothermal amplification and detection system called isothermal target and probe amplification (iTPA) by employing DNA-RNA-DNA chimeric primers and a FRET (fluorescence Resonance Energy Transfer) probe. The iTPA method is based on a combination of novel isothermal

chain amplification (ICA) and FRET cycling probe technology (CPT) (Fig. 3).

or TaqMan PCR (Mullah *et al*., 1998).

**A)** 

**B)** 

Fig. 2. Real-Time PCR detection of amplicons

**1.2.3 Isothermal PCR** 

Present commercial detection system for *Salmonella* spp. can be classified into four categories. The first, traditional method which uses culture medium and observe colony morphology formed on it. This requires at least four days and experienced skill to perform biological tests, but it is the only common method authorized throughout the world for now.

The second, Enzyme-Linked Immuno-Sorbent Assay (ELISA) detects certain bacteria using immune reaction between antibody and antigen specific for them. This method is easy to use because it makes color change or forms lines but it can be applied only for those which has specific toxin protein and requires more than 106 CFU / ml for detection which needs 16 hours of incubation. The third, Adenosine triphosphate (ATP) detection kit detects level of bacterial contamination by the amount of ATP in sample. This method can not be used for identification of bacteria because it can only tell including the total amount of ATP from food. This is usually used for comparing hygiene level before and after washing. The fourth, genetic method which is based on PCR is highly specific and sensitive enough to detect 100 CFU / ml of bacteria, but at the same time it can detect even the dead cells after processing or cooking food because of the high sensitivity.
