Attachment and biofilm formation on stainless steel by Escherichia coli O157:H7 as affected by curli production

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Abstract
Aims: The aim of this study was to determine the role of curli in attachment and biofilm formation by Escherichia coli O157:H7 on stainless steel. Methods and Results: Three curli-deficient strains (43895−, 43894− and E0018−) and three curli over-producing strains (43895+, 43894+ and E0018+) of E. coli O157:H7 were studied. Stainless steel coupons (SSC) were immersed in cell suspensions of each strain for 24 h at 4°C. The number of cells attached to SSC was determined. To determine the ability of attached cells to form biofilm, SSC were immersed in 10% of tryptic soya broth up to 6 days at 22°C. Curli-deficient and curli-producing strains did not differ in their ability to attach to SSC, but only curli-producing strains formed biofilms. Conclusions: Curli production by E. coli O157:H7 does not affect attachment of cells on stainless steel but curli-producing strains are better able to form biofilms. Significance and Impact of the Study: Curli production by E. coli O157:H7 enhances its ability to form biofilm on stainless steel, thereby potentially resulting in increased difficulty in removing or killing cells by routine cleaning and sanitizing procedures used in food-processing plants.