Aims:  To assess the ability of Listeria monocytogenes to form biofilm on different food‐contact surfaces with regard to different temperatures, cellular hydrophobicity and motility. Methods and Results:  Forty‐four L. monocytogenes strains from food and food environment were tested for biofilm formation by crystal violet staining. Biofilm levels were significantly higher on glass at 4, 12 and 22°C, as compared with polystyrene and stainless steel. At 37°C, L. monocytogenes produced biofilm at significantly higher levels on glass and stainless steel, as compared with polystyrene. Hydrophobicity was significantly (P < 0·05) higher at 37°C than at 4, 12 and 22°C. Thirty (68·2%) of 44 strains tested showed swimming at 22°C and 4 (9·1%) of those were also motile at 12°C. No correlation was observed between swimming and biofilm production. Conclusions:  L. monocytogenes can adhere to and form biofilms on food‐processing surfaces. Biofilm formation is significantly influenced by temperature, probably modifying cell surface hydrophobicity. Significance and Impacts of the Study:  Biofilm formation creates major problems in the food industry because it may represent an important source of food contamination. Our results are therefore important in finding ways to prevent contamination because they contribute to a better understanding on how L. monocytogenes can establish biofilms in food industry and therefore survive in the processing environment.

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Staphylococcus aureus (S.aureus) is a pathogenic bacterium capable of developing biofilms on food processing surfaces, a pathway leading to cross contamination of foods. The purpose of this study was to evaluate the ability of S.aureus to form biofilm on food processing surfaces (polystyrene and stainless steel) with regard to different temperatures (12 and 37°C) and cellular hydrophobicity. Biofilm assays were performed on n. 67 S.aureus isolates from food, food processing environments and food handlers and n. 3 reference strains (S.aureus ATCC 35556, S.aureus ATCC 12600 and S.epidermidis ATCC 12228). A strain-specific variation in biofilm formation within S.aureus strains tested was observed. At 37°C, n. 38/67 (56.7%) of strains were biofilm producer in at least one tested surface. A total of n. 25/38 (65.7%) of strains were biofilm producer on polystyrene whereas n. 24/38 (63.1%) were biofilm producer on stainless steel. Moreover, n. 11/38 (28.9%) of strains were biofilm producers on both selected surfaces. The majority of S.aureus strains which produced biofilms (n. 17/38-44.7%), were isolated from food environments. At 12°C, only one S.aureus strain from food handler (S.aureus 374) was biofilm producer. Cell surface hydrophobicity level increased with temperature. Additionally, a statistically significant difference (P<0.001) was found between hydrophobicity at 37°C and 12°C. Finally, the architecture of biofilm formed by S.aureus strains on polystyrene and stainless steel surfaces at selected temperatures was observed by scanning electron microscopy. The appearance of thick extracellular products in strongly (S.aureus ATCC 35556 - positive control) and the absence of those products in the non-biofilm producer (S.epidermidis ATCC 12228 - negative control) is presented

The foodborne pathogen Listeria monocytogenes is a concern in food safety because of its ability to form biofilm and to persist in food industry. In this mini-review, the issue represented by this pathogen and some of the latest efforts performed in order to investigate the composition of biofilms formed by L. monocytogenes are summarized.

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