title: Attachment of Listeria innocua to polystyrene: effects of ionic strength and conditioning films from culture media and milk proteins.
abstract: It is recognized that bacterial adhesion usually occurs on conditioning films made of organic macromolecules absorbed to abiotic surfaces. The objectives of this study were to determine the extent to which milk protein-coated polystyrene (PS) pegs interfere with biofilm formation and the synergistic effect of this conditioning and hypertonic growth media on the bacterial adhesion and biofilm formation of Listeria innocua, used as a nonpathogenic surrogate for Listeria monocytogenes. PS pegs were uncoated (bare PS) or individually coated with whey proteins isolate (WPI), β-lactoglobulin, bovine serum albumin, or tryptic soy broth (TSB) and were incubated in bacterial suspensions in modified Welshimer's broth. After 4 h, the number of adherent cells was dependent on the coating, as follows: TSB (10(7) CFU/ml) > bare PS > β-lactoglobulin > bovine serum albumin ∼ WPI (10(4) CFU/ml). The sessile cell counts increased up to 24 h, reaching > 10(7) CFU per peg for all surfaces (P > 0.1), except for WPI-coated PS; this indicates that the inhibitory effects of milk protein conditioning films are transient, slowing down the adhesion process. The 4-h bacterial adhesion on milk protein-coated PS in modified Welshimer's broth supplemented with salt (0 to 10% [wt/vol]) did not vary (P > 0.1), indicating that conditioning with milk proteins was the major determinant for inhibition of bacterial adhesion and that the synergetic effect of salt and milk proteins on adhesion was minimal. Moreover, the presence of 5 to 10% salt significantly inhibited 24-h biofilm formation on the TSB-coated and bare PS, with a decrease of >3 log at 10% (wt/vol) NaCl and almost completely depleted viable sessile bacteria on the milk protein-coated PS.
authors.affiliation: Food Research and Development Centre, Agriculture and Agri-Food Canada, 3600 Casavant Boulevard West, Saint-Hyacinthe, Quebec, Canada J2S 8E3. gilles.robitaille@agr.gc.ca.
authors.forename: Gilles
authors.initials: G
authors.lastname: Robitaille
authors.affiliation: Food Research and Development Centre, Agriculture and Agri-Food Canada, 3600 Casavant Boulevard West, Saint-Hyacinthe, Quebec, Canada J2S 8E3.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Choinière
authors.affiliation: Atlantic Food and Horticulture Research Centre, Agriculture and Agri-Food Canada, 32 Main Street, Kentville, Nova Scotia, Canada B4N 1J5.
authors.forename: Timothy
authors.initials: T
authors.lastname: Ells
authors.affiliation: Food Research and Development Centre, Agriculture and Agri-Food Canada, 3600 Casavant Boulevard West, Saint-Hyacinthe, Quebec, Canada J2S 8E3.
authors.forename: Louise
authors.initials: L
authors.lastname: Deschènes
authors.affiliation: Food Research and Development Centre, Agriculture and Agri-Food Canada, 3600 Casavant Boulevard West, Saint-Hyacinthe, Quebec, Canada J2S 8E3.
authors.forename: Akier Assanta
authors.initials: AA
authors.lastname: Mafu
mesh_terms: D001422:Bacterial Adhesion / Q000502:physiology*; D018441:Biofilms / Q000254:growth & development*; D015169:Colony Count, Microbial; D003470:Culture Media / Q000737:chemistry / Q000494:pharmacology*; D005516:Food Microbiology; D008087:Listeria / Q000502:physiology*; D008894:Milk Proteins / Q000494:pharmacology*; D009994:Osmolar Concentration; D011137:Polystyrenes
chemical_list: D003470:Culture Media; D008894:Milk Proteins; D011137:Polystyrenes