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.

Effect of surface conditioning with cellular extracts on Escherichia coli adhesion and initial biofilm formation

“…This conditioning layer also enhanced the anti-corrosion performance of the coatings (He et al, 2015). Additionally, other authors have shown that protein films reduced the bacterial adhesion to different surfaces (Chapman et al, 2001;Dat et al, 2014;Merghni et al, 2016;Robitaille et al, 2014).…”

Surface conditioning with <em>Escherichia coli</em> cell wall components can reduce biofilm formation by decreasing initial adhesion

“…Although one might think that adsorbed cell components and related molecules can automatically enhance cell retention and reduce surface hygiene, it is known from several studies that proteins such as bovine serum albumin (BSA), gelatin, fibrinogen and pepsin adsorbed to surfaces may inhibit bacterial attachment [11],[12],[13]. Recently, it has been shown that surface preconditioning has potential to prevent bacterial adhesion to processing surfaces [14]–[18]. In order to elucidate about the process of bacterial contamination in dairy industry, Dat et al [16] investigated the influence of surface conditioning with dairy by-products such as skimmed milk, buttermilk and butter serum (which possess different compositions) on the bacterial attachment behavior.…”

Influence of Incubation Temperature and Total Dissolved Solids on Biofilm and Spore Formation by Dairy Isolates of Geobacillus stearothermophilus

“…In 1993, Helke et al (18) concluded that casein, a-lactalbumin, and b-lactoglobulin inhibited the attachment of Listeria monocytogenes and Salmonella enterica serovar Typhimurium to stainless steel and Buna-N surfaces when present in the attachment menstruum or when the surfaces were pretreated with these proteins. Conditioning films made of whey protein isolate (WPI), b-lactoglobulin, and bovine serum albumin (BSA) have been shown to have a transient effect by slowing down the adhesion of Listeria innocua to polystyrene surfaces (19). Individual milk proteins a-casein, b-casein, κ-casein, and a-lactalbumin have been known to reduce the attachment of Staphylococcus aureus and L. monocytogenes to stainless steel surfaces (20).…”