Surface roughness of stainless steel influences attachment and detachment of Escherichia coli O157

Determining the influence of surface roughness on Escherichia coli 0157 attachment to and detachment from stainless steel (SS) is important for controlling this foodborne pathogen. The aim of this study was to evaluate the interactions of six E. coli strains (four O157:H7, one O157:H12, and one O1:H7) with SS type 304 finishes of various surface roughness: 2B (unpolished surface), 4 (common food grade SS), and 8 (polished smooth surface). In attachment assays (exposure to cell suspensions with periodic swirling), bacteria were enumerated by epifluorescence microscopy, and in detachment assays a blotting technique and atomic force microscopy (AFM) were used. Attachment data suggest that E. coli attach in greater numbers to significantly smoother SS8; however, detachment assays and AFM data suggest cells are more easily removed from this finish. Conversely, attachment to SS2B was lower, and AFM data suggest that E. coli O157 may adhere more strongly to this finish. Attachment and detachment data for SS4 was variable, suggesting complex attachment mechanisms to this type of SS. SS4 is the most common material used in food processing facilities. The data from this study indicate that bacterial interactions with SS4 are complex and less easily predicted than those with SS of other finishes, including 2B and 8. These differences in bacterial attachment may be of concern to the food industry and warrant further investigation.