ZnO nanoparticles enhance the efficiency of sodium hypochlorite disinfectant in reducing the adhesion of pathogenic bacteria to stainless steel surfaces

Abstract

The use of commercial disinfectant in combination with other antimicrobial agent such as ZnO nanoparticles to improve disinfection efficacy could be a promising strategy in the control of pathogenic bacteria. In this context, the aim of study was to determine the minimum inhibitory concentration (MIC) of sodium hypochlorite disinfectant, ZnO nanoparticles as well as Mn-, Ce-, and Co-doped ZnO nanoparticles (doping concentrations 10%, 20%, 30%) against gram-negative bacteria Escherichia coli and Salmonella Typhimurium, and gram-positive bacteria Staphylococcus aureus and Listeria monocytogenes using the broth microdilution method CLSI M07-A10, while the checkerboard microdilution method was carried out to assess the type interaction of sodium hypochlorite in combination with pure ZnO nanoparticles. The results specified that ZnO nanoparticles were agents that required higher concentrations to inhibit bacterial growth than sodium hypochlorite, whereby a synergistic effect was achieved in their combination. It was also revealed that doping of Mn and Co in ZnO nanoparticles improved antibacterial activity against gram-positive bacteria. Generally, this study aimed to evaluate the effectiveness of individual treatments (sodium hypochlorite and ZnO nanoparticles) and their combination on initial bacterial adhesion to stainless steel surfaces (AISI 304) exposed to different temperatures (7 °C, 25 °C, 37 °C) and pH (4.5, 7.0, 8.5) using colony-forming units count method. It was evident that ZnO nanoparticles were more effective than sodium hypochlorite in reducing bacterial adherence, while the combined tretmant showed a better effect than any individual treatment alone, highlighting its advantages as a novel disinfectant to prevent bacterial biofilms. Furthermore, data that temperature and pH affected bacterial adhesion provide comprehensive insight how bacteria survive in the food processing environments, which could assist in assessment the risk of contamination.