( Two-dimensional Optimization of a Semi...)Two-dimensional Optimization of a Semi-nested PCR,,, for Detecting Listeria monocytogenes

Two-dimensional Optimization of a Semi-nested PCR
for Detecting Listeria monocytogenes

Bacterial enteritides, which are triggered by contaminated foodstuffs, pose a significant health risk for consumers. The legally prescribed food tests are intended to prevent such products from finding their way into retail outlets. However, microbiological tests usually take several days since the pathogenic bacteria are often present in very low numbers in relation to the overall number of bacteria, which means that selective enhancement steps must be carried out prior to the actual detection reactions.

Among the problem bacteria is Listeria monocytogenes, a gram-positive, rod-shaped, facultative anaerobic bacterium. L. m. is ubiquitous and normally enters foodstuffs during processing and packaging. Milk and milk products are commonly affected by this bacteria.

The Austrian milk hygiene decree stipulates that L. m. must not be present in untreated cow's milk that is intended for human consumption, cheese (with the exception of hard cheeses), pasteurized milk or any other dairy products.

The standard method for detecting L. m. is the IDF (International Dairy Federation) method, although the test requires up to seven days. Modern molecular biology methods enable results to be obtained rapidly. The publication by Allmann et al. (1995) presents various, PCR*-based systems for detecting pathogenic microorganisms in dairy products.