The effects and physiological phenotypic changes in Escherichia coli O157:H7 induced into VBNC state by hydrogen...

Hydrogen peroxide and silver ions (HPS) is an emerging disinfectant widely used for sanitizing food contact surfaces and equipment. Escherichia coli O157:H7 is a major foodborne pathogen that represents a significant threat to public health. This study systematically evaluated the impact of growth medium (LB broth and beef broth, a food model) and temperature (25 °C and 37 °C) on the HPS-induced formation of the viable but non-culturable (VBNC) state in E. coli O157:H7 biofilms. The results indicated that, upon complete entry into the VBNC state following treatment with the same concentrations of HPS (1:40 and 1:80 dilutions), the biofilms cultured in beef broth formed the fewest VBNC state cells, at 9.26 ± 3.27 % and 13.36 ± 1.73 %, respectively, while those cultured at 37 °C formed the most VBNC state cells, at 22.60 ± 2.39 % and 23.81 ± 1.87 %, respectively. Compared to untreated cells, VBNC state cells exhibited elevated reactive oxygen species (ROS) levels, increased activities of superoxide dismutase (SOD) and catalase (CAT), reduced intracellular ATP concentrations, and depolarized membrane potentials, indicating oxidative stress and diminished metabolic activity. Morphologically, VBNC cells showed shrinkage, rough and unevenly wrinkled surfaces, and reduced cell volumes relative to untreated cells. Resuscitation of VBNC state cells was achieved within 24 h upon incubation in LB broth, LB broth supplemented with 2.0 mg/mL pyruvate, or beef broth. These findings underscore food safety risks from HPS-induced VBNC E. coli O157:H7 in biofilms, offering insights for safe HPS application in the food industry.