Disinfection efficacy of slightly acidic electrolyzed water sprayed on Salmonella on the chicken manure contaminated eggs

Abstract: Salmonella enteritidis (S. enteritidis) infection has been recognized as one of the most common bacterial causes of human gastroenteritis worldwide, and was closely associated with eggs. Slightly Acidic Electrolyzed Water (SAEW), as an environmentally-friendly disinfectant, was often be studied in disinfecting eggshell surfaces to remove dirt and pathogenic microorganisms. However, the efficiency of SAEW was often be affected by the presence of manure. In our study, disinfection efficiency of SAEW in spraying treatment method was evaluated on manure and S. enteritidis mixture contaminated eggs, to verify if this method could be used to alleviate the interference of chicken manure on disinfection effectiveness. Eggs were first sprayed with different solutions (H2O、ERW and SAEW) to clean the manure in different times (6, 12, 18 and 24 s), and then sprayed with different disinfectants (H2O、ERW and SAEW) with different available chlorine concentration (ACC, 5, 15, 25 and 35 mg/L) in different times (6, 12, 18 and 24 s). Eggs were divided into 5 groups: H2O+H2O group (Sterilized H2O sprayed for cleaning and disinfection treatment), ERW+ERW group (ERW single sprayed for cleaning and disinfection treatment), ERW+SAEW group (ERW sprayed for cleaning treatment, then SAEW used for disinfection treatment) and SAEW+SAEW group (SAEW single sprayed for cleaning and disinfection treatment). The inactivation models of SAEW+SAEW and ERW+SAEW group with different ACCs, cleaning times and disinfection times were developed using multiple linear regression analysis. After treatment, decontamination of eggs with SAEW single sprayed group showed an equivalent or higher bactericidal effect compared to other treatments. A complete inactivation of S. enteritidis (6.26 lg cfu/egg) on the surface of shelled egg samples resulted from SAEW+SAEW group and ERW+SAEW group at an ACC of 25 and 35 mg/L for 18 and 24 s, respectively. Moreover, the established model of SAEW+SAEW and ERW+SAEW group had a good fit-quantified by the determination coefficient R2 (0.933 and 0.926) and adjusted R2 (0.930 and 0.923). The model was validated with additional random 8 conditions within the experimental domain. The predicted value showed a good agreement with the actual values, for the points of response values were very close to the line of 100% correlation. The model was valid and the results demonstrated that the cleaning time, disinfection time and ACC significantly affected the S. enteritidis. enteritidis reduction (P < 0.01). In addition, the ACC was ranked as the most important factor in the three factors by analysing the parameter coefficients in the model equation. As previously stated, manure was a strong limiting factor for disinfection of SAEW due to it can react with HClO in SAEW in an oxidative manner, resulting in a reduction of the ACC. From another point of view, it also meaned that manure could be effectively removed by the SAEW. Therefore, SAEW also has a good organic removal function as well as an excellent disinfection function. In conclusion, our results demonstrated that the SAEW could be used in disinfecting manure contaminated eggshell surfaces to remove S. enteritidis in single sprayed treatment way.