Bactericidal effect of chlorous acid water against enterohemorrhagic Escherichia coli

Background Enterohemorrhagic Escherichia coli (EHEC) is an important etiologic 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 chlorite (HClO2)-based disinfectant, on EHEC of three major serogroups (O157, O26 and O111) and compared its bactericidal activity with that of sodium hypochlorite (NaClO). Results CAW with >25 mg/L free available chlorine (FAC) achieved a >4 log10 CFU/ml reduction in the numbers of all tested EHEC strains after 1 min of treatment, while >500 mg/L FAC in NaClO was needed to obtain the equivalent effects. CAW with low FAC concentrations (5 or 10 mg/L) showed a time-dependent increase in EHEC cell reduction even under high organic matter load, whereas NaClO required a FAC threshold to achieve an efficient bactericidal effect. Discussion The results in this study indicate that CAW is more effective than NaClO in the presence of organic matter. CAW with >20 mg/L FAC reduced the number of EHEC O157 cells adhering to bean sprouts by >3 log10 after 30 min of treatment, indicating that CAW is a suitable sanitizer for food processing.