Anneluise Mader

Improved sample treatment protocol for accurate detection of live Salmonella spp. in food samples by viability PCR

Culture-based detection is still considered as the standard way for detection of Salmonella in foods, although molecular methods, such as viability PCR (vPCR), have been introduced to overcome some disadvantages of traditional culture methods. Despite the success of the vPCR methodology, the problem of false-positive results is a major drawback, especially when applied to environmental samples, hindering the interpretation of the results. To improve the efficiency of vPCR, many approaches have been introduced by several authors during the last years. In the present work, the combination of PEMAX dye, double tube change, and double photo-activation step was established as a strategy to improve vPCR protocol. By combining these approaches, we developed an improved sample treatment protocol able to neutralize DNA signals of up to 5.0×107 dead cells/sample from both pure culture and artificially contaminated food samples. Our results indicate that vPCR can work reliable and has a potential for high throughput detection of live Salmonella cells in food samples, minimizing false-positive signals.

Model for the Assessment of Microbiological Risks Originating from Intentional Contaminations in Feed Chains

A model for the assessment of microbiological risks, which may originate from intentional contamination of the feed chain, was developed by the Federal Institute for Risk Assessment. It covers different feed processing chains and different microorganisms. Numerous scenarios were defined and evaluated as well as a sensitivity analysis performed. The application of the model allowed the identification of process parameter combinations which would be inefficient in worst case scenarios, e.g. where a highly heat resistant strain was selected for the intentional contamination. Equally important, this analysis can help to target specific control efforts. Based on the outcome of these simulations, recommendations can easily be given in crisis situations to which temperature-time combination processes should be adjusted to ensure the production of safe compound feeding stuff. This research will help to better understand and predict the consequences of bioterrorist attacks in the feed processing chain.