## 1 Introduction  
The genus _Listeria_ comprises Gram-positive facultative anaerobic rod-shaped bacteria with a marked capacity to inhabit a variety of environmental niches and animal hosts, determined by their ability to withstand physicochemical stressors and activate persistence mechanisms. These characteristics make _Listeria_ spp. prone to colonizing food production plants and contaminating foodstuff. _Listeria monocytogenes_ is an intracellular pathogen that can cause invasive infections, such as septicemia, meningitis, and endocarditis, and is 99% foodborne in immunocompromised persons, the elderly, pregnant women, and newborns. This pathogen can also cause abortion in humans and animals [1; 2; 3]. Upon _L. monocytogenes_ infection, healthy adults do not develop symptoms or manifest a gastrointestinal illness that is usually undiagnosed [4]. Pregnancy listeriosis, after a two- to three-week incubation period, can manifest as a self-limiting illness with flu-like symptoms. However, the bacterium can cross the placenta and infect the fetus with consequences such as spontaneous abortion, preterm birth, stillbirth, and newborn infections. These complications were reported in 80% of listeriosis cases in pregnant women [5]. _L. monocytogenes_ is classified in the four phylogenetic lineages I, II, III, and IV, in which 13 serotypes comprising different sequence types (STs) and clonal complexes (CCs) are distributed. About 95% of isolates from food and infection cases belong to serotypes 1/2a, 1/2b, 1/2c, and 4b, among which 1/2b and 4b serotypes belonging to lineage I are more frequently associated with human clinical cases. Strains of lineage II are more common in food and food processing plants, while those belonging to lineages III and IV are isolated mainly from animals. The internalin A, a cell wall-anchored protein encoded by the _inl_A gene, is considered the main virulence factor in the hypervirulent strains of _L. monocytogenes_[6]. A recent systematic review and meta-analysis focused on data from South Korea reported that most foodborne listeriosis outbreaks were caused by serotypes 1/2b and 1/2a [7]. In the European Union (EU), 2738 cases of listeriosis were confirmed in 2022 with a fatality rate of 18.1%, the highest compared to previously reported data, which increased to 2952 confirmed cases, 96.5% hospitalizations and a 19.7% fatality rate in the year 2023 according to the most recent reports on zoonotic diseases in the EU [8; 9]. In 2022, 2770 confirmed listeriosis cases, including 17 strong-evidence and 18 weak-evidence foodborne outbreaks that affected 296 persons, with 242 hospitalizations and 28 deaths, were reported by 30 European countries through The European Surveillance System (TESSy). Whole-genome sequencing (WGS) reported to TESSy showed small but long-lasting multi-country epidemiological clusters that persisted for several years. The ECDC-EFSA One Health WGS System, already at the end of 2022, defined that more than one-third of the multi-country outbreak isolates matched non-human isolates, showing the potential of WGS application in identifying the origin of the outbreaks [4]. In the meat, fish/seafood, dairy, and fruit/vegetable sectors _L. monocytogenes_ represents one of the main microbiological food contamination threats due to its capacity to persist in the food and feed processing environment (FFPE). Obstacles to eliminating persistent _L. monocytogenes_ in the FFPE are insufficient hygiene barriers and inadequate equipment design, cleaning, and disinfection procedures. To identify possible contamination by _L. monocytogenes_, a well-designed environmental sampling program (EMP) must be implemented that also involves the facility personnel. Further, in the case of persistent _L. monocytogenes_ detection, a'seek-and-destroy' approach must be applied, namely, the application of cause analysis and corrective actions to eliminate the contamination at specific sites.