Source attribution of Listeria monocytogenes genotypes in meat processing facilities

Listeria (L.) monocytogenes is a zoonotic pathogen with a high mortality rate (20-30%) and therefore requires special attention. The cause of transmission lies in the fact that the pathogen forms reservoirs in food and the food environment, which is why measures must be taken. This will be achieved through the cooperation of stakeholders, i.e. the food producing companies and the evaluating institutes. The companies should learn from the data they have to obtain from environmental monitoring as part of their self-monitoring. This means deriving measures to reduce L. monocytogenes in the environment and to eliminate hypervirulent L. monocytogenes on the premises. We know that there is hypo- and hypervirulent L. monocytogenes that are present in the environment as well as in facilities. Some of them are highly infectious, have adapted to their environment and persist. The purpose of this study is to describe this situation using typing data from two companies and to make the data as simple as possible so that it can be quickly assessed and used retrospectively by a quality management team. For this purpose, 297 isolates from two companies were used, which were characterized by MLST. A rapid screening focusing on the abcZ, bglA and Idh alleles is used as a predictor of the clonal complex (CC), which can be used to determine whether the CCs are hypo- or hypervirulent. In a second step, the data set is plotted over space, niche, and time to determine whether persistent clones are present. Hypervirulent clones are eliminated first, followed by virulent ones. And in the case of persistent clones, special cleaning concepts may need to be considered. Testing the effectiveness of the biocides used against persistent strains helps indirectly.