Modelling the Effect of Salt Concentration on the Fate of Listeria monocytogenes Isolated from Costa Rican Fresh Cheeses

Assessment of the Anti-Listeria Effect of Citrus limon Peel Extract In Silico, In Vitro, and in Fermented Cow Milk During Cold Storage

In this study, the antimicrobial effect of Citrus limon peel extract against Listeria monocytogenes was analyzed in silico, tested in vitro, and validated in fermented cow milk during cold storage. The in silico analysis revealed that 4,5-di-O-caffeoyquinic acid interacts with L. monocytogenes proteins involved in colonization and intracellular survival. The in vitro experiments demonstrated that the anti-Listeria activity of Citrus limon peel extract is primarily attributed to limonene and phenolic compounds. In fermented milk stored at 4 °C for 7 days, the addition of Citrus limon peel extract resulted in a 2 Log reduction of L. monocytogenes compared to the control. Using the Baranyi and Roberts model, a significant decrease in the maximum growth rate (-0.021 h-1) and the concentration of L. monocytogenes from 5.95 to 3.67 log CFU/mL was observed in fermented milk supplemented with a 2×MIC level of Citrus limon peel extract during storage at 4 °C. The findings from all three approaches highlighted that the inhibitory effect of Citrus limon peel extract against L. monocytogenes is primarily due to chlorogenic acid derivatives, especially 4,5-di-O-caffeoyquinic acid, and limonene. Beyond its antimicrobial properties, the supplementation of fermented milk with Citrus limon peel extract also enhances the milk antioxidant capacity and total organic acids content.

Genome-Based Characterization of Listeria monocytogenes, Costa Rica

Genomic data on the foodborne pathogen Listeria monocytogenes from Central America are scarce. We analyzed 92 isolates collected during 2009-2019 from different regions in Costa Rica, compared those to publicly available genomes, and identified unrecognized outbreaks. Our findings suggest mandatory reporting of listeriosis in Costa Rica would improve pathogen surveillance.

Listeria in Food: Prevalence and Control

Listeria monocytogenes is a foodborne pathogen characterized by its psychrotrophic and ubiquitous nature as well as its ability to survive and proliferate in a wide range of harsh environments and foods [...].

Combination of growth conditions and InlB-specific dot-immunoassay for rapid detection of Listeria monocytogenes in raw milk

The gram-positive bacterium Listeria monocytogenes is an important foodborne pathogen contaminating dairy products. Closely related to L. monocytogenes saprophytic Listeria spp. are also frequent contaminators of food and, particularly, dairy products. To distinguish L. monocytogenes from nonpathogenic Listeria spp. and other bacteria, a dot-immunoassay was developed. The immunoassay is based on the polyclonal antibody to the secreted form of the surface virulence-associated L. monocytogenes-specific InlB protein. To increase InlB production, bacteria were grown on the brain-heart infusion agar supplemented with 0.2% activated charcoal (BHIC agar). Direct plating of artificially contaminated raw milk samples on the BHIC agar followed by the dot-immunoassay allowed a rapid identification of L. monocytogenes in concentrations as little as 10 cfu/mL. Using the developed approach, preliminary results were obtained within 14 h, and the final results were obtained after 26 h. The dot-immunoassay was tested on L. monocytogenes strains belonging to different clonal complexes and phylogenetic lineages, Listeria spp., and other bacterial species. Results showed the exceptional specificity of the developed dot-immunoassay for the rapid identification of L. monocytogenes.