Informative Value of a Sample Investigation with a Predefined Sample Size using the Example of Listeria monocytogenes in Food Safety.

Foodborne diseases, especially those caused by zoonotic agents, pose a significant threat to human health. Food business operators are therefore responsible for producing safe food. To do this, they must regularly carry out appropriate sample investigations to detect zoonotic agents in their food before it leaves the factory. Depending on the issue investigated, there may be legal requirements for food business operators, usually specifying minimum sample sizes, such as Commission Regulation (EU) No 2073/2005. However, in most cases, there is no information on the precision, and therefore, on the significance of the results for these sample sizes. Regulatory veterinary authorities have a control function and, as a result, they are required to regularly evaluate the available investigations and their results. In addition, in certain crisis situations (e.g., foodborne outbreaks or suspected food contamination), authorities may guide food business operators in their investigations and conduct their own investigations to assess food safety measures. In such cases, as there are no legally defined sample sizes to be taken, the appropriate sample sizes must be determined by the authorities. This can lead to a conflict between the need for feasibility and the need for conclusiveness of the investigation potentially being a challenge for the regulatory authority in charge. This paper highlights the importance of thoughtful study design and the critical communication of available results by veterinary authorities on the background of a use case involving Listeria monocytogenes findings in a crisis situation. Using the minimum sample size, n = 5, required by Commission Regulation (EU) No 2073/2005 for the pathogen Listeria monocytogenes as a guide, the uncertainties associated with small sample sizes are highlighted. It also aims to facilitate the evaluation of studies performed and the assessment of further sample sizes.