Retrospective Analysis of the Results of Five Consecutive Proficiency Tests Organized by the German National Reference Laboratory for Listeria monocytogenes.

Listeria (L.) monocytogenes is an environmental pathogen that can contaminate a wide variety of food products, leading to foodborne listeriosis outbreaks. In this context, ready-to-eat (RTE) foods of animal and plant origin are of particular relevance as the source of infection. In Germany, the official food and veterinary control laboratories, under the sovereignty of the federal states, examine foodstuffs for the presence of foodborne pathogens, including Listeria. The German National Reference Laboratory for L. monocytogenes regularly organizes inter-laboratory proficiency tests (PTs) to monitor the accuracy and comparability of analyses performed by these official control laboratories. In our study, we provide summary data on frequently contaminated RTE food products in the European Union and present the outcome of five consecutive PTs. RTE food matrices provided by the German National Reference Laboratory for L. monocytogenes included processed meat, fish, vegetable, and dairy products. Overall, the official control laboratories achieved excellent results in the PTs. In total, 91 participants were documented. Flawless results were reported in 93.4% of the cases. Only four times, participants did not pass the PT in the first attempt. By performing official food and veterinary controls along the food chain, control laboratories make a significant contribution to food safety. To keep the excellent standard of the official control laboratories in Germany in line with future challenges in food safety, PTs with relevant RTE food matrices are indispensable.