Surfactant-disinfectant resistance of Salmonella and Staphylococcus adhered and dried on surfaces with egg compounds

To confirm the importance of eliminating food sediments from the surfaces of food-related environments, we examined the resistance of pathogenic bacteria (Salmonella Typhimurium and Staphylococcus aureus) cells, dried and adhered on glass with 25% w/v egg albumen, 25% yolk or 50% whole egg solutions, against benzalkonium chloride and alkyldiaminoethylglycine hydrochloride. Bacterial suspensions (0.1 ml of 8 log cfu/ml) were put on 47 mmφ glass dishes and dried at room temperature (20–24 °C) for 180 min in a bio safety cabinet with ventilation. Although the viable cells in distilled water decreased 2.0 (S. aureus)–3.5 (S. Typhimurium) log fold during the drying period, the egg compounds protected the bacteria. The disinfectant treatments (2.0 mg/ml for 10 min) showed a clear bactericidal effect in the absence of egg compounds. However, the bactericidal effect disappeared in the presence of yolk and whole egg. Imaging before and after drying and the disinfectant treatments were carried out using a phase-contrast microscope and an atomic force microscope. The protective effect of egg compounds on bacterial viability disappeared with a proper washing process.

► We examined the resistance of bacteria dried with egg on glass against disinfectants.
► Yolk protected the dried Salmonella and Staphylococcus from the disinfectant.
► These effects in cell suspension were observed with a phase-contrast microscope.
► Adhered cells and egg compounds were observed by an atomic force microscopy.
► The protective effect of egg compounds disappeared with a proper washing process.