Diverse Listeria monocytogenes in-house clones are present in a dynamic frozen vegetable processing environment

Pracser, Nadja; Zaiser, Andreas; Ying, Hui Min Katharina; Pietzka, Ariane; Wagner, Martin; Rychli, Kathrin

doi:10.1016/j.ijfoodmicro.2023.110479

Cited by 4 publications

(4 citation statements)

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“…Additionally, ST224-CT5623 clustered together in a phylogenetic tree ( Supplementary Figure S3 ; Supplementary Table S5 ). Moreover, ST224-CT5623 isolates were identified in a previous study as in-house clones surviving for years in the frozen vegetable facility, indicating their re-occurrence in processing lines of “Packaging Room B” over time ( Pracser et al, 2024 ).…”

Section: Resultsmentioning

confidence: 99%

“…This study aimed to investigate the presence of Listeria in biofilms and characterize the co-existing microbiota in the processing environment of a European frozen vegetable processing facility, where L. monocytogenes in-house clones persisted for years ( Pracser et al, 2024 ). We collected all samples after cleaning and disinfection to assess the hygiene status of the processing environment while avoiding the presence of food residues, which would interfere with the analysis of extracellular matrix components of biofilms.…”

Section: Discussionmentioning

confidence: 99%

“…Both MLST-STs were prevalent in the same frozen vegetable processing environment in our previous study. ST224-CT5623 was identified as an in-house clone in the packaging area, specifically in “Packaging Room B” ( Pracser et al, 2024 ). Our findings, combined with the results of our previous research, clearly show that ST224-CT5623 is still present after multiple cleaning and disinfection cycles.…”

Section: Discussionmentioning

confidence: 99%

“…Our previous study confirmed the presence of in-house clones in a European frozen vegetable-producing environment. However, no differences in the stress resistance gene pattern were observed between in-house and non-in-house clones ( Pracser et al, 2024 ). Other factors that could support the persistence of L. monocytogenes in food processing environments include biofilms and interactions with co-occurring microbiota ( Møretrø and Langsrud, 2017 ; Tan et al, 2019 ; Finn et al, 2023 ).…”

Section: Introductionmentioning

confidence: 93%

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Exploring the occurrence of Listeria in biofilms and deciphering the bacterial community in a frozen vegetable producing environment

Pracser,

Voglauer,

Thalguter

et al. 2024

Front. Microbiol.

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The establishment of Listeria (L.) monocytogenes within food processing environments constitutes a significant public health concern. This versatile bacterium demonstrates an exceptional capacity to endure challenging environmental conditions in the food processing environment, where contamination of food products regularly occurs. The diverse repertoire of stress resistance genes, the potential to colonize biofilms, and the support of a co-existing microbiota have been proposed as root causes for the survival of L. monocytogenes in food processing environments. In this study, 71 sites were sampled after cleaning and disinfection in a European frozen vegetable processing facility, where L. monocytogenes in-house clones persisted for years. L. monocytogenes and L. innocua were detected by a culture-dependent method at 14 sampling sites, primarily on conveyor belts and associated parts. The presence of biofilms, as determined by the quantification of bacterial load and the analysis of extracellular matrix components (carbohydrates, proteins, extracellular DNA) was confirmed at nine sites (12.7%). In two cases, L. innocua was detected in a biofilm. Furthermore, we explored the resident microbial community in the processing environment and on biofilm-positive sites, as well as the co-occurrence of bacterial taxa with Listeria by 16S rRNA gene sequencing. Pseudomonas, Acinetobacter, and Exiguobacterium dominated the microbial community of the processing environment. Using differential abundance analysis, amplicon sequence variants (ASVs) assigned to Enterobacterales (Enterobacter, Serratia, unclassified Enterobacteriaceae) and Carnobacterium were found to be significantly higher abundant in Listeria-positive samples. Several Pseudomonas ASVs were less abundant in Listeria-positive compared to Listeria-negative samples. Acinetobacter, Pseudomonas, Janthinobacterium, Brevundimonas, and Exiguobacterium were key players in the microbial community in biofilms, and Exiguobacterium and Janthinobacterium were more relatively abundant in biofilms. Further, the microbial composition varied between the different areas and the surface materials.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%