DNA Probe

Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all living organisms. Ribonucleic acid or RNA is a nucleic acid polymer consisting of nucleotide monomers that plays several important roles in the processes that translate genetic information from DNA. As DNA and RNA of organisms are specifically different between each other, by identifying the DNA and RNA of organisms can then be used to isolate and identify. Foodborne pathogen can be detected when DNA or RNA of the food samples are complementary to the nucleotide sequence in the probe. If DNA or RNA of food samples match that of the DNA probe, a complex is formed and thus a positive results.

New DNA probe assays for detection of Salmonella, Listeria, E. coli and Staphyococcus aureus use non-isotopically labelled DNA probe to detect specific ribosomal RNA targets of organisms. Test samples will first undergo lysis, using alkaline or enzymatic reagents which cause the cells to burst and die. Probes are then added to the test samples to form probe-target complexes; in solution form. These complexes formed and hybridized will be captured onto polystyrene sticks to separate the desired components from the unwanted cellular and sample debris. Hybridization is a process of combining complementary, single-stranded nucleic acids into a single molecule. The single molecule thus produced would then be detected after hybridization by its intrinsic properties (e.g., fluorescence) or through recognition by a specific antibody. If detection is by intrinsic properties, the polystyrene sticks will be incubated with solution containing an anti-fluroescein antibody-horseradish peroxidase conjugate and a mixture of tetramethyl benzidine/hydrogen peroxide. After reaction ceased, results can then be obtained by determining the absorbance of samples at a specific wavelength (usually 450nm) using photometer instrument or other optical devices.