Food grade disinfectants based on hydrogen peroxide/peracetic acid and sodium hypochlorite interfere with the adhesion of Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Listeria monocytogenes to stainless steel of differing surface roughness

This study aimed to evaluate the potential of the bacterium Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Listeria monocytogenes to adhere to stainless steel discs with differing degrees of surface roughness (Ra = 25.20-961.90 nm). Stainless steel is a material commonly used in the food industry for processing equipment, which is regularly exposed to cleaning procedures. The investigation included the commercial disinfectants hydrogen peroxide/peracetic acid and sodium hypochlorite which were evaluated for their antibacterial and anti-adhesion activity. The adhesion was assessed by the standard plate count method, while the broth microdilution method CLSI M07-A10 was used to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the disinfectants. Based on the MIC values, both disinfectants exerted significant inhibitory effects with MIC values for hydrogen peroxide/peracetic acid and sodium hypochlorite of 250 mu g ml(-1) and 500 mu g ml(-1), respectively. Whereas the MBC values were equal to the MIC for all bacteria except for E. coli with values 2-fold higher than the MIC. Obtained results also revealed that all tested bacteria were able to adhere to stainless steel surfaces, although differences were found for strains and surface roughness. The lowest adhesion rate of each strain was recorded on the roughest stainless steel disc at a Ra of 961.90 nm. Further, at a concentration of 1 MIC, the disinfectant sodium hypochlorite reduced initial bacterial adhesion to stainless steel surfaces to a significantly greater extent than the disinfectant hydrogen peroxide/peracetic acid. These findings are consistent with the results obtained by Scanning Electron Microscopy (SEM) analysis, which indicates the great applicability of the tested disinfectants for the control of bacterial adhesion in the food industry.