Listeria monocytogenes is of great concern as a foodborne pathogen. Many ready-to-eat foods are widely contaminated with this organism and have caused listeriosis outbreaks and sporadic cases in many countries. In Japan, there is a high incidence of L. monocytogenes contamination, specifically in raw ready-to-eat seafood. Identical L. monocytogenes subtypes have been isolated repeatedly from samples of food manufactured at a given store or processing plant, and researchers suspected that certain L. monocytogenes isolates have formed biofilms at these sites. A microtiter plate biofilm formation assay was conducted, and all raw ready-to-eat seafood isolates tested were able to form biofilms to various degrees. Biofilm formation by L. monocytogenes isolates of lineage I was significantly greater (P = 0.000) than that by isolates of lineage II. However, isolates of clonal lineages formed different levels of biofilms, indicating that the ability to form a biofilm is affected positively or negatively by environmental factors.
Aims: To clarify the cellular properties of Listeria monocytogenes involved in adhesion to and biofilm formation on polyvinyl chloride, a widely used material in the food manufacturing process.
Methods and Results: A significant correlation between the ability of initial adherence to and biofilm formation on PVC was observed for 24 L. monocytogenes strains (Spearman rank‐correlation coefficient, rs = 0·89). The swimming motility assay revealed no relationship between initial adherence and motility of L. monocytogenes. The microbial adhesion to solvent assay revealed an interaction of L. monocytogenes cells with nonpolar solvents, and a significant correlation was also observed between the degree of interaction with nonpolar solvents and initial adherence to PVC (rs = 0·87 and rs = 0·84, between initial adherence and affinities to decane and hexadecane, respectively).
Conclusions: Results indicate that cellular hydrophobicity of L. monocytogenes is an important property involved in the initial adherence to and biofilm formation on PVC.
Significance and Impact of Study: This study clarified the factors involved in the adherence to and biofilm formation ability of L. monocytogenes strains with PVC.
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