Contamination of kitchen surfaces due to bacteria present in foodstuffs is one of the main causes of foodborne outbreaks. Salmonella infections are an important cause of foodborne disease, and Salmonella Enteritidis is the most common isolate in the past few years. In this study, the adhesion ability of four Salmonella Enteritidis isolates to different materials (polyethylene, polypropylene, and granite) used in kitchens was compared. The results indicated that the two plastic materials were generally less prone to colonization than was the granite. As surface properties of both bacteria and materials are a determinant in the adhesion process, surface hydrophobicity was determined through contact angle measurement, and the roughness of the materials was evaluated through the R(a) and R(z) values by a noncontact laser stylus tracing. The four Salmonella strains showed similar degrees of hydrophilicity, while the materials were hydrophobic, with granite having a very low degree of hydrophobicity (deltaG(lwl) = -4.7 mJ/m2). However, the different extents of adhesion could not be explained in terms of surface hydrophobicity and roughness of the materials tested. The main conclusion to be drawn is that Salmonella adhesion is strongly strain dependent, despite the similar degree of hydrophobicity displayed by all the strains assayed, and this can constitute a factor of virulence among the different serotypes.

Adhesion of microorganisms to food processing surfaces and the problems it causes are a matter of strong concern to the food industry. Contaminated food processing surfaces may act as potential sources of transmission of pathogens in food industry, catering and in the domestic environments. Several studies have shown that adhesion of bacteria to surfaces partly depends upon the nature of the inert surfaces and partly upon the bacterial surface properties. The aim of this study was to compare the adhesion of four different strains of Salmonella Enteritidis to stainless steel 304 (SS 304). The effect of surface hydrophobicity and surface elemental composition on the adhesion process was also analysed. Hydrophobicity was evaluated through contact angle measurements using the sessile drop method. All the strains studied showed positive values of the degree of hydrophobicity (ΔGlwl) and so can be considered hydrophilic while stainless steel revealed a hydrophobic character. Bacterial cell surface composition was measured using X-ray photoelectron spectroscopy (XPS). The XPS results corroborated the similarity of the values of the degree of hydrophobicity obtained by contact angles. The different Salmonella strains showed similar elemental composition and cell surface physico-chemical properties. Nevertheless, S. Enteritidis MUSC presented higher adhesion ability to SS 304 (p<0.05). It can be concluded that the physico-chemical properties of the strain does not explain the ability of adhesion to stainless steel. Other factors like the production of polysaccharides must be considered.

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Vegetable sanitization protocols recommend the use of chlorine, which has adverse effects on the environment and carcinogenic effects on humans. Acetic acid is an interesting alternative to chlorine because it possesses no risk to human health and is widely available in the form of vinegar. This study aimed to evaluate the sanitizing action of vinegar, 130 g L-1 total titratable acidity expressed as acetic acid, on lettuce. Vinegar was chosen because it is a low-cost product widely available in the Brazilian market. The minimum inhibitory concentration and minimum bactericidal concentration of vinegar against Escherichia coli were 2.5 and 15 g L-1 total acidity, respectively. Lettuce leaves artificially contaminated with E. coli or naturally contaminated with total coliforms were washed with water and immersed in vinegar solution (15 g L-1 total acidity) for 15 min. This period was sufficient to reduce E. coli counts in artificially contaminated samples and total coliforms in naturally contaminated samples. There were no visual changes in lettuce leaves, which indicates that vinegar at 15 g L-1 total acidity can be used to sanitize vegetables without affecting their appearance.