Role of curli fimbriae in mediating the cells of enterohaemorrhagic Escherichia coli to attach to abiotic surfaces

Abstract

Aims: The objectives of this study were to evaluate the role of curli in assisting the cells of enterohaemorrhagic Escherichia coli (EHEC) in attaching to abiotic surfaces and to determine the influence of cell-surface contact time on the efficiency of the attachment. Methods and Results: Three pairs of EHEC cultures, each with a curli-expressing and a noncurli-expressing variant (O111:H- 7-57C⁺ and O157:H7 5-9C⁻, O157:H7 5-11C⁺ and 5-11C⁻, as well as O103:H2 7-52C⁺ and 7-52C⁻), were allowed to interact with polystyrene, glass, stainless steel and rubber surfaces at 28°C for 24 h (short-term attachment) or 7 days (long-term attachment). The quantities of the cells that attached to the surfaces were measured daily in the long-term attachment study, and in 4 h intervals in the short-term attachment study. Quantification of the cells that attached to the surfaces was accomplished with a crystal violet binding assay. The results of the long-term attachment study indicated that 7-57C⁺ attached to the polystyrene and glass surfaces more efficiently (P < 0·05) than did 5-9C⁻. The curli-expressing variant of 5-11 possessed a better ability to adhere to the polystyrene and glass surfaces than did its noncurli-expressing counterpart (P < 0·05). The differences in attachment between 7-52C⁺ and 7-52C⁻ on polystyrene and stainless steel surfaces were statistically significant (P < 0·05). However, the attachment of the pair on the glass surfaces was statistically insignificant (P > 0·05). In addition, the two members of all three EHEC pairs attached equally well to rubber surfaces (P > 0·05). In the short-term attachment study, only the pair of 7-52 attached differently on glass and stainless steel surfaces (P < 0·05). Conclusions: These results suggest that curli could be an important cell surface component to mediate the attachment of some EHEC cells to certain abiotic surfaces. Cell-surface contact time could have a significant influence on EHEC attachment to abiotic surfaces. Significance and Impact of the Study: The study signifies a possible role of curli in assisting the cells of EHEC in attaching to food-contact surfaces. It underlines the importance of cleaning and sanitizing food-contact surfaces regularly and thoroughly, and of identifying chemical agents that can effectively remove the attached EHEC cells from these surfaces.