Foodborne pathogens represent a significant public health burden. Quantifying the relative importance of various potential sources of foodborne infection is challenging due to data scarcity and uncertainty in empirical studies. Structured expert judgment (SEJ) provides a valuable methodological alternative to gain insights into source attribution of foodborne pathogens. We conducted a SEJ study to attribute human cases of 26 foodborne pathogens in the Netherlands to seven major transmission pathways, 20 food groups, and two animal groups, in a typical post-COVID19 year, using Cooke's classical model. The elicitation process involved snowball recruitment, expertise self-assessment, and a workshop where experts answered calibration questions to capture their uncertainty as input for the model. Subsequently, experts completed the target questions to obtain attributable proportions at the 'kitchen door' level. Results indicated that transmission was predominantly (>50%) foodborne for Staphylococcus aureus, Listeria monocytogenes, Yersinia spp., Bacillus cereus, Clostridium perfringens, certain non-typhoidal Salmonella serotypes, Campylobacter spp., hepatitis E virus and Toxoplasma gondii, whereas person-to-person transmission was the primary pathway for astrovirus, rotavirus, norovirus, and sapovirus. Brucella spp. and typhoidal Salmonella were attributed primarily (>85%) to international travel. All other pathogens showed attributions of <50% to any individual pathway. Substantial differences were observed when dividing foodborne transmission into food groups. Key contributors included food handlers and vermin, various meats (e.g., pork, beef, chicken), and shellfish. These SEJ-derived estimates complement existing data by providing pathogen-specific insights in the Dutch context.

Chicken broth-based extracellular metabolomics reveals phase-dependent metabolic shifts of Listeria monocytogenes under refrigeration.

Fluorescence spectroscopy for monitoring inactivation of Salmonella enterica and Listeria monocytogenes by plasma-activated water in vegetable wash water

Listeria monocytogenes (L. monocytogenes) is a pathogenic bacterium that poses a significant threat in food safety due to its ability to form resilient biofilms, contributing to cross-contamination risks in food processing environments. This study examines the role of the hly gene on biofilm formation and antibiotic resistance in L. monocytogenes. By generating a hly deletion mutant (Lm-Δhly), we investigated how the absence of this gene affects bacterial behavior and biofilm development. Our results revealed that hly deletion did not impact bacterial growth but significantly impaired biofilm formation. The Lm-Δhly strain exhibited a reduced biofilm biomass and a looser biofilm structure compared to the wild-type (WT) strain. Microscopic analysis, including SEM and CLSM, confirmed that biofilm architecture was compromised, with more viable cells in the WT biofilms and a substantial decrease in extracellular polymeric substances (EPS) in the mutant strain. Furthermore, the Lm-Δhly strain displayed reduced motility, auto-aggregation, and surface hydrophobicity, indicating a reduced ability to adhere and disseminate. Gene expression analysis revealed downregulation of key virulence factors such as prfA, sigB, and quorum sensing (QS) genes in the Lm-Δhly strain, suggesting that hly plays a role in their regulation. Antibiotic susceptibility testing revealed that the Lm-Δhly strain was more sensitive to ribosome-targeting antibiotics, including tetracycline and roxithromycin, correlating with impaired biofilm development under antibiotic stress. These findings emphasize the importance of hly in biofilm development, antibiotic resistance, and virulence regulation in L. monocytogenes. Targeting hly or its associated pathways may be a promising strategy to combat persistent L. monocytogenes contamination in food-related environments. Further investigation into hly' interactions with broader regulatory networks is needed to fully elucidate its role in L. monocytogenes pathogenesis.

Biofilm formation and intra-pulsotype variability of Listeria monocytogenes at temperatures relevant to food processing environments.

The principles of employing antimicrobial compounds in active packaging: Mechanisms, applications, and future directions

Sodium chloride induces filamentation in Listeria monocytogenes grown in culture medium and cooked pork.

Thermal treatments are typically applied to milk to ensure microbial safety but can cause degradation of some bioactive proteins. Ultraviolet-C (UV-C) irradiation is an alternative treatment that can increase microbial safety and may better preserve some bioactive proteins. However, the effect of UV-C doses validated to provide ≥5-log reduction of bacteria in bovine milk on the preservation of bioactive milk proteins remains unknown. We determined the UV-C dose (fluence) required for ≥5-log inactivation of vegetative bacteria (E. coli O157: H7, Listeria monocytogenes, Salmonella Typhimurium and Staphylococcus aureus) and bacterial spores (Bacillus cereus, Bacillus subtilis) inoculated into raw bovine milk. We compared the retention of bioactive proteins (lactoferrin (Lf), immunoglobulin (Ig) G, IgM, IgA) after exposure to UV-C doses required for ≥5-log inactivation of vegetative bacteria and spores with commercially used high-temperature short-time (HTST) and ultra-high temperature (UHT) processing via ELISA. Achieving ≥5-log reductions of all four vegetative bacteria required 14kJ/L (termed UV-1), whereas 40kJ/L were required for ≥5-log reductions of all bacterial spores (termed UV-2). 14kJ/L retained IgG at higher levels than HTST (p<0.05) and preserved Lf and IgM at similar levels to HTST (p>0.05), while IgA preservation was lower than HTST (50.6% vs. 62.0%; p<0.05). 40kJ/L resulted in improved preservation of all bioactive proteins tested compared with UHT. The findings establish that UV-C may be a promising approach for processing whole bovine milk, particularly for enhancing bioactive protein preservation after spore-reduction treatment compared with the current industry standard (UHT).

Viable but Nonculturable Listeria monocytogenes May Resuscitate After Transfer From Stainless Steel Biofilms to Vacuum-Packed Smoked Herring.

Biopreservation potential of Carnobacterium maltaromaticum strains against Listeria monocytogenes in plant-based cheese analogs

Cooked meat products, particularly ham, are widely consumed, and reducing nitrite levels has become a priority due to health concerns and regulatory pressure. This study evaluated the microbiological safety, technological performance, physicochemical properties, and sensory attributes of whole cooked ham formulated with reduced nitrite (from 150 to 80ppm) during shelf life. Microbiological analyses were conducted every 15days, including total viable counts (TVC), lactic acid bacteria (LAB), Enterobacteriaceae, Staphylococcus aureus and Escherichia coli. TVC and LAB remained below the safety threshold (<104CFU/g), while all other parameters were below detection limits. Sulphite reducing Clostridium spores, Salmonella spp. and Listeria monocytogenes were absent from all samples. Challenge testing with L. monocytogenes and Clostridium sporogenes was performed to assess the product's ability to inhibit pathogen growth under simulated storage conditions (up 35 and 90days, respectively) and temperature abuse conditions (8°C). The reduced-nitrite ham formulation effectively inhibited the growth of C. sporogenes and delayed the growth of L. monocytogenes. Technological assessments included colour measurements, water retention capacity, and texture profile analysis (TPA), with no significant differences observed between the standard and nitrite reduced formulations (P>0.05). Physicochemical parameters such as pH (6.0-6.2), water activity (aw, 0.9669-0.9482), and residual nitrite content (4 to 1mg/kg) were evaluated at 0, 45 and 90days. These findings demonstrate that reducing nitrite levels to 80ppm can ensure the product safety and quality, as evidenced by stable physicochemical properties and the preservation of sensory characteristics such as appearance, odour, texture, and flavour.

Performance assessment of a predictive microbiology framework for Listeria monocytogenes growth in dry-cured fish

Insights on the microbial resistance mechanisms of Listeria monocytogenes to Pulsed Electric Fields (PEF) treatments.

Listeria monocytogenes causes listeriosis, a severe foodborne disease with a high hospitalization rate. This pathogen forms robust biofilms in food environments and poses significant health risks. Bacillus subtilis PS-216, a proven surfactin producer with antimicrobial activity against Gram-negative pathogens, was investigated for its anti-Listeria effects. We analyzed the antimicrobial and antibiofilm activities of wild-type B. subtilis PS-216 and knockout mutants lacking quorum sensing genes (ΔcomQ, ΔcomA) and QS-regulated antimicrobials (ΔsrfAA, ΔbacA, ΔsrfAAΔbacA) against L. monocytogenes and L. innocua. Gene expression of comQ, srfAA, and bacA was analyzed using YFP promoter fusions in mono- and cocultures. B. subtilis PS-216 demonstrated potent antimicrobial activity against Listeria sp., achieving a strong log reduction (5.9 and 6.7 log for L. monocytogenes and L. innocua, respectively) in coculture. The ComQXPA quorum sensing system centrally regulates this anti-Listeria activity by coordinated surfactin and bacilysin production. Both compounds are essential for a strong antagonistic effect, with coculture triggering enhanced expression. Additionally, B. subtilis PS-216 effectively inhibits Listeria biofilm formation, with surfactin preventing lawn-type biofilms. The similar response patterns between L. monocytogenes and L. innocua support the use of L. innocua as a suitable surrogate, though species-specific differences exist. These findings highlight B. subtilis PS-216's broad-spectrum probiotic potential and provide mechanistic insights for optimizing strategies to control L. monocytogenes in food processing environments.

Biosynthesis of silver nanoparticles using Duea ching (Ficus botryocarpa Miq.) fruit extract: Characteristics, bioactivities and application in active chitosan/gelatin films for enhancing the shelf life of baby clam.

Comprehensive evaluation of Listeria monocytogenes phage lysin Lys-LP-XY2101 for food biocontrol, biofilm removal, and safety

Control of Listeria monocytogenes ATCC 19115 biofilm formation and virulence by a food-derived Lactobacillus acidophilus VBFDP771 isolate with predictive assessment of robustness

Biocontrol of Listeria monocytogenes in milk: Isolation and characterization of a novel bacteriophage cocktail

• Evolved resistant variants of L. monocytogenes EGD-e emerged under antibiotic stress • Ciprofloxacin resistant variants displayed cross-protection to heat in skimmed milk • Mutations in genes related to antibiotic target and efflux pumps are involved • Mutation in stress response genes seems to be related to oxytetracycline resistance • Mutations in cell wall-related genes are suggested to increase thermoresistance The extensive use of antibiotics in primary production has promoted the emergence of resistant bacteria. Due to cross-protection phenomena, these antimicrobial resistant (AMR) bacteria may also withstand food preservation treatments applied in the food industry. This study aimed to evaluate the emergence of resistant variants (RVs) of Listeria monocytogenes EGD-e after prolonged exposure to antibiotics (amoxicillin, ciprofloxacin and oxytetracycline) based on adaptive laboratory evolution assays. RVs were selected by determining the minimum inhibitory concentration, then characterized phenotypically against heat treatments (58 °C/ 20 min) and genotypically to identify mutations responsible for changes in thermoresistance. Five ciprofloxacin RVs (Lm Cip1-5 ) and one oxytetracycline RV (Lm Oxy ) were obtained. Several ciprofloxacin RVs showed greater thermoresistance in McIlvaine buffer (pH 7.0) than the parental strain, also observed in skimmed milk (pH 6.8). Mutations identified in codY (Lm Oxy ) and fepR and parC (ciprofloxacin RVs) are likely responsible for the antibiotic resistance. Moreover, mutations in genes linked to cell wall biosynthesis ( rml ), metabolism and RNA or energy processing (e.g., cshA, atpA2, lmo2794 ) may contribute to increased thermoresistance. These findings highlight the interaction between AMR and cross-protections mechanisms, and the potential risk posed by AMR bacteria in the food chain, which could compromise the traditional preservation methods.

Unpasteurized fruit juices in developing countries pose significant public health risks due to potential contamination with foodborne pathogens, particularly in rural areas where reliable energy for thermal processing is lacking. This study evaluates the natural acidity of passion fruit juice as a non-thermal strategy to inactivate Salmonella ser. Typhimurium, Escherichia coli O157:H7, and Listeria monocytogenes. Pathogens were inoculated into passion fruit juice at pH 2.9, 3.4, and 3.9, and their survival was monitored at 25 °C (room temperature) and 5 °C (refrigerated). Log-linear and Weibull models were used to predict inactivation kinetics, targeting a 5-log reduction in accordance with FDA requirements. At pH 2.9 and 5 °C, S. Typhimurium and E. coli achieved a 5-log reduction within 8 h, while L. monocytogenes required 24 h to achieve the same reduction level. The Weibull model provided a superior fit (R2 &gt; 0.94) at pH 2.9 and 3.4, accurately capturing the nonlinear inactivation dynamics. Increasing pH to 3.9 significantly slowed inactivation, underscoring the critical role of low pH. These findings suggest that the inherent acidity of passion fruit juice provides a practical, energy-independent method for controlling pathogenic bacteria in developing regions, preserving nutritional quality without thermal processing.