Molecular Characterization of Serratia marcescens Strain Isolated from Yellow Mealworms, Tenebrio molitor , in The Netherlands.

Insect culture has developed rapidly worldwide; it faces important security and safety control issues, including animal infections and disease development. In the Netherlands, in 2021, a ~30% mortality of mealworms, , occurred at one farm, where over-humid sites in the substrate were observed. Bacterial cultures from both the external and internal partsof fry and larger mealworms were identified by MALDI-TOF to predominantly and . Due to the important role of as a potential zoonotic bacterium, we performed a molecular characterization of the isolated strain. Genomic analysis showed a multidrug-resistant isolate carrying a (41), (6')-, and SST-1 chromosomal class C beta-lactamase-resistantgenes, all located on the chromosome. Additionally, several virulence genes were identified. The phylogenetic tree revealed that the strain from this study was similar to other strains from different ecological niches. Although the entomopathogenic activity was not confirmed, this case demonstrates that can act as a reservoir and as an alternative path for exposing clinically important antibiotic-resistant bacteria that can affect animals and humans. It underlines the need to keep management factors optimal, before insects and their products enter the feed and food chain.