Apply new nucleic acid-based technologies to detection.

Diagnostic techniques are in a time of change. Molecular diagnostic techniques have evolved, along with advances made in the field of molecular biology, during the last two decades. Molecular techniques are more sensitive than classical techniques and more specific as well. Unlike traditional diagnostic methods, molecular methods use reagents and reactions that are derived from living organisms. They offer a spectrum of new tools and approaches to microbial analysis.

Several challenges persist when scientists analyze microorganisms found in foods, particularly when their research involves studying complex communities of microbes. Nucleic-acid based techniques may be helpful when approaching new questions about microbial communities. Researchers at the Norwegian Food Research Institute have developed several new methods in the field of nucleic acid-based microbial analyses. These methods involve both sample preparation and detection.

The new sample preparation technique involves simplifying the DNA purification process through the use of paramagnetic beads. The same paramagnetic beads are used for both cell separation and DNA purification, which makes it possible to have a fully automated process.

The separate detection of viable and dead bacteria is a major issue in nucleic acid-based diagnostics. The Norwegian scientists have applied a living-dead dye that both binds covalently to DNA and also inhibits the polymerase chain reaction (PCR) from dead cells. In addition, they have developed a DNA array-based detection assay. The assay combines the specificity obtained by enzymatically labeling DNA probes with the potential for detecting several targets simultaneously by using DNA array hybridization. This is a promising tool for microbial community analyses when used in combination with the 16S rDNA amplification technique.

On a related front, the researchers have developed a novel approach for multiplex quantitative PCR. The multiplex PCR has been combined with their DNA array-based detection method. And the scientists are optimizing a system for monitoring microbial growth and death in real time. The system involves tagging bacteria with green fluorescent protein, and detecting the fluorescence using a high-resolution confocal laser scanner.

The scientists are in the process of developing a complete platform for microbial community analyses. They want to use this platform as a service both for the food industry and academia. The platform will be ready in early 2005.

Further information. K. Rudi, Matforsk, Norwegian Food Research Institute, Osloveien 1, N-1430 As; email: [e-mail]; URL: http://www.matforsk.no/.