Chlorine Dioxide Is an Effective Disinfectant Against Enterohemorrhagic Escherichia coli, Enteropathogenic E. coli and Escherichia albertii.

Chlorine dioxide (ClO2) is used as a disinfectant in food and environmental sanitation. However, information regarding its efficacy against enterohemorrhagic Escherichia coli (EHEC) under organic load conditions remains limited. This study evaluated the bactericidal activity of aqueous ClO2 against clinically important EHEC serogroups and compared its efficacy with that of sodium hypochlorite (NaClO). Additionally, other bacterial strains, including enteropathogenic E. coli (EPEC), Escherichia albertii, and E. coli type strains, were also examined. Under organic load conditions, treatment with 100 ppm NaClO resulted in only minor reductions (< 1 log10 CFU/mL) within 60 s for all strains tested. In contrast, 10 ppm ClO2 reduced the E. coli type strain and E. albertii by > 3 log10 CFU/mL, while 100 ppm ClO2 reduced all tested strains to below the detection limit (> 6 log10 CFU/mL reduction). EHEC and EPEC strains showed lower susceptibility to 10 ppm ClO2 (0.2-1.3 log10 CFU/mL reduction) but were reduced to below the detection limit by 100 ppm ClO2. Time-course assay further demonstrated that 100 and 30 ppm ClO2 inactivated > 6 log10 CFU/mL of EHEC within 15 and 30 s, respectively, whereas NaClO showed only limited bactericidal activity over the same period. These results demonstrate that ClO2 provides substantially greater and more rapid bactericidal activity than NaClO against EHEC in the presence of organic matter. The findings provide quantitative evidence of the concentration- and time-dependent bactericidal efficacy of ClO2 and provide fundamental information for future studies evaluating its potential application in food hygiene and environmental sanitation.