ORIGINAL ARTICLE Influence of temperature on biofilm formation by Listeria monocytogenes on various food-contact surfaces: relationship with motility and cell surface hydrophobicity G. Di Bonaventura 1,2 , R. Piccolomini 1,2 , D. Paludi 3 , V. D’Orio 3 , A. Vergara 3 , M. Conter 4 and A. Ianieri 4 1 Center of Excellence for Aging, ‘‘G. d’Annunzio’’ University Foundation, Chieti, Italy 2 Department of Biomedical Sciences, ‘‘G. d’Annunzio’’ University of Chieti-Pescara, Chieti, Italy 3 Department of Food Science, University of Teramo, Teramo, Italy 4 Department of Animal Production and Food Safety, University of Parma, Parma, Italy Introduction Listeria monocytogenes is a Gram-positive aerobic to facul- tative anaerobic bacterium that is an important food- borne pathogen (Farber and Peterkin 1991; Korber et al. 1994; Vazquez-Boland et al. 2001; Moltz and Martin 2005). This organism causes severe nonenteritic disease (meningitis and septicemia) in the immunocompromised host and abortion in pregnant women (Doyle et al. 1997). Listeriosis is a rare food-borne disease, despite the fact that exposure to L. monocytogenes is probably very common because of its wide distribution in the environ- ment and presence in the food industry (Doyle et al. 1997). The bacterium can be isolated from soil, vegeta- tion, faecal matter, sewage, water and animal feed. Because of its ubiquitous nature, L. monocytogenes is fre- quently isolated from food and food-processing environ- ments (Donnelly 2001; Moltz and Martin 2005). Numerous studies have shown that L. monocytogenes is capable of adhering and forming biofilm on food-contact surfaces (Blackman and Frank 1996) such as polystyrene, glass and stainless steel. The formation of biofilms creates Keywords biofilm, food-contact surfaces, hydrophobicity, Listeria monocytogenes, motility, temperature. Correspondence Giovanni Di Bonaventura, Center of Excellence for Aging, ‘‘G. d’Annunzio’’ University Foundation, Via Colle dell’Ara, 66013 Chieti, Italy. E-mail: giovannidibo@hotmail.com 2007 ⁄ 0958: received 19 June 2007, revised 31 October 2007 and accepted 31 October 2007 doi:10.1111/j.1365-2672.2007.03688.x Abstract Aims: To assess the ability of Listeria monocytogenes to form biofilm on differ- ent food-contact surfaces with regard to different temperatures, cellular hydro- phobicity and motility. Methods and Results: Forty-four L. monocytogenes strains from food and food environment were tested for biofilm formation by crystal violet staining. Bio- film 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 bio- film at significantly higher levels on glass and stainless steel, as compared with polystyrene. Hydrophobicity was significantly (P <0Æ05) higher at 37°C than at 4, 12 and 22°C. Thirty (68Æ2%) of 44 strains tested showed swimming at 22°C and 4 (9Æ1%) 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-pro- cessing surfaces. Biofilm formation is significantly influenced by temperature, probably modifying cell surface hydrophobicity. Significance and Impacts of the Study: Biofilm formation creates major prob- lems 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. Journal of Applied Microbiology ISSN 1364-5072 1552 Journal compilation ª 2007 The Society for Applied Microbiology, Journal of Applied Microbiology 104 (2008) 1552–1561 ª 2007 The Authors