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

Aims: The aim of this study was to determine the role of curli in attachment and biofilm formation by Escherichia coli O157:117 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 O157:117 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.