Slightly acidic electrolyzed water induces Staphylococcus aureus to enter the VBNC state: differences between...

S. aureus is a common foodborne pathogen that poses a great danger to the food industry and human health. Slightly acidic electrolytic water (SAEW) is characterized by strong antimicrobial effect and high potential for application. In this study, the effect of SAEW on the formation of VBNC state of S. aureus was systematically evaluated, and the differences in the formation of VBNC state of S. aureus in planktonic and biofilm states were also analyzed by flow cytometry. The results showed that treatment of S. aureus in planktonic and biofilm states with 0.8 mg/L SAEW resulted in complete loss of culturability at 2.5 h and 2.0 h, respectively, with 3.56 ± 0.28 % and 4.81 ± 0.13 % of cells formed VBNC state. And both states of VBNC S. aureus could be resuscitated, and the planktonic VBNC state S. aureus resuscitated faster. ATP concentration, ROS level and respiration intensity of different states of bacteria were examined, compared with uninduced bacteria, VBNC S. aureus showed increased ATP concentration and ROS level, and decreased catalase activity, esterase activity, and respiratory intensity. Meanwhile, the overall metabolic level of the biofilm VBNC state bacteria was lower than that of the planktonic VBNC state bacteria, and its ROS level was higher than that of the planktonic VBNC state bacteria. Gene expression was determined by RT-qPCR, and the results showed that the transcript levels of genes regulating N-acetylglucosamine metabolism were up-regulated and those related to lipid metabolism, antioxidant and respiratory metabolism were down-regulated in the VBNC state S. aureus. This study comprehensively evaluates the application effect of SAEW in the food industry to provide a scientific basis for its safe and effective use; deepens the understanding of the mechanism of the formation of VBNC states by bacteria in different states, and provides theoretical support for the control of VBNC bacteria.