Molecular and environmental indicators of Listeria monocytogenes persistence: a multi sector approach
Year: 2026
Type: conference-paper
Abstract: IntroductionListeria monocytogenes (Lm) is a bacterial foodborne pathogen able to persist for long periods in food processing environments, particularly through biofilm formation. This persistence results from complex interactions between strain genetic characteristics and environmental conditions. The aim of this study was to identify molecular and environmental indicators associated with the persistence of L. monocytogenes across several high-risk food production sectors.Materials and methodsThree environmental sampling campaigns were conducted in nine food processing facilities belonging to three high-risk sectors (seafood, vegetables, and pork). A total of 1,097 samples were analyzed for the presence of L. monocytogenes, along with the collection of environmental and microbiological data (total aerobic mesophilic flora, pH, relative humidity, temperature, biocide residues, presence of debris, surface type and condition…). Lm isolates were characterized by WGS and classified as persistent or transient (≥2 campaigns, ≤7 allelic differences by cgMLST). Machine learning approaches and pangenome analysis were used to identify determinants associated with persistence.Results and conclusionL. monocytogenes was detected in 114 out of 1,097 samples (10.40%), with higher prevalence in the vegetable sector (51/357), followed by pork (35/360) and seafood (28/380). From these 114 samples, 12 persistent clusters, comprising 67 strains, were identified. The clonal complex CC121 was particularly represented, although other CC (CC31, CC101, CC5, CC412, and CC155) were also associated with persistence profiles. Pangenome analysis showed that persistence is not linked to a single genetic determinant but rather to a combination of biological functions, including prophage-related loci, transport systems (TatA, TatC, EfeO), and stress adaptation mechanisms. In contrast to previous assumptions, no direct association was observed between biofilm formation and persistence phenotype through quantitative crystal violet characterization. Persistent isolates were mainly found in environments with higher total aerobic mesophilic flora levels, typically above ~5.3–6.0 log10 CFU/mL (e.g., non-food-contact surfaces), compared to ~3.8–4.7 log10 CFU/mL for transient isolates. Similarly, persistent isolates were associated with higher relative humidity levels, often around ~80–85% (e.g., non-food-contact surfaces), compared to ~68–78% for transient isolates. These results suggest that the high levels of total aerobic mesophilic flora and humid conditions favor the establishment and maintenance of persistent clones. Overall, these findings indicate that L. monocytogenes persistence results from the interaction between strain genetic characteristics andsite-specific environmental conditions. This study highlights the value of an integrated approach combining genomic data and detailed environmental characterization to improve monitoring and control strategies of Lm in food processing environments.
Source: HAL
Language: English
Subfield: Food Science
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7224980939