Bactericidal effect of chlorous acid water against enterohaemorrhagic Escherichia coli

Background. Enterohaemorrhagic Escherichia coli (EHEC) is an important aetiologic agent of foodborne illness. Since the main source of EHEC is contaminated meat and fresh produce, these ingredients should be sanitized using methods that achieve efficient mitigation of bacterial load under organic-matter-rich conditions. Materials and Methods. We examined the effect of chlorous acid water (CAW), which is a chlorous acid (HClO 2 )-based disinfectant, on seven major serotypes of EHEC, including O157, O111, O26, O91, O103, O121 and O145, and compared its bactericidal activity with that of sodium hypochlorite (NaClO). Results. Both sanitizers rapidly inactivated all EHEC strains to below the detection limit at low free available chlorine (FAC) concentrations (5–10 mg l −1 ). However, organic matter significantly hampered the bactericidal activity of NaClO. In the presence of simulated blood or excretion contamination, CAW demonstrated superior stability and sustained bactericidal efficacy compared with NaClO. While NaClO lost its activity rapidly due to the consumption of FAC by organic matter, CAW maintained an effective concentration and achieved significant bacterial reduction. Furthermore, in EHEC biofilm assays, CAW exhibited potent bactericidal activity, achieving a >7-log reduction of viable cells within the biofilm, whereas NaClO showed limited efficacy under the same conditions. Discussion. The results suggest that CAW is a robust alternative to NaClO, particularly in environments with high organic burdens and biofilm contamination, such as food processing facilities and healthcare settings.