The effect of surface structures on the physicochemical characteristics and attachment capability of Salmonella

Salmonella enterica, one of the most important foodborne pathogens, is often acquired through the consumption of contaminated food of animal origin such as poultry and eggs. In Australia, Salmonella enterica subspecies II 4,12:b- (S. Sofia) is the predominant serovar isolated from poultry. Salmonella Sofia may be regarded as having relatively low virulence for humans as it is rarely associated with human disease in comparison with subspecies I serovars. Salmonella have been recovered from a wide range of food contact surfaces and equipment because of their ability to attach to different surfaces in the food processing environment. Understanding how Salmonella attach to different surfaces may provide insight into their potential persistence within food environments and their subsequent contamination of foods. Bacterial attachment is influenced by a number of bacterial surface properties, including physicochemical characteristics, surface structures and protein expression. The aims of this study were to: 1) characterise the surface properties of 25 Salmonella isolates including reference strain S. Typhimurium ATCC 14028. Most strains studied were from poultry (22 out of 25 isolates) although human isolates (three out of 25 isolates) were also included. The strains used in this study, represent the four most common serovars (S. Sofia (n=14), S. Typhimurium (n=6), S. Infantis (n=3) and S. Virchow (n=2)) isolated from poultry in Australia; 2) determine the role of these surface properties in the initial attachment of Salmonella to glass, stainless steel, plastic, Teflon¬¨vÜand rubber; 3) determine if surface structures, such as outer membrane proteins (OMP) and cellulose, could influence the hydrophobicity and attachment ability of bacteria to different surfaces and 4) investigate whether the initial attachment of Salmonella to glass, stainless steel, Teflon¬¨vÜand chicken skin was a stochastic process or not. The experimental stochastic attachment data was also compared to the extended Derjaguin-LandauVerwey-Overbeek (XDLVO) theory to determine if the theory can predict initial attachment.