Biochemical Techniques and Instrumentation

Detection of Salmonella by PCR

The polymerase chain reaction (PCR) is an in vitro DNA amplification of the target sequence within few hours. In this assay, the sample (target DNA) is allowed to react with a pair of primers (specific for each microbe), deoxyribonucleoside triphosphate, reaction buffer and Taq DNA polymerase. If the primers are complementary to the target DNA, a new DNA strand will be synthesized. During each cycle, the DNA strand is doubled. Each cycle consists of three segments, viz. a denaturation step, during which the two primers attach to the complementary target sequences and a synthesis step, during which a new strand in synthesized with the help of dNTPs and enzyme. Recently, this technique has been used for specific detection of various bacterial and viral pathogens from seafood samples. A detailed procedure is given below for the PCR detection of Salmonella from seafood samples using an internationally accepted invA gene.