Comparison of the Effectiveness of Acidified Sodium Chlorite and Sodium Hypochlorite in Reducing Escherichia coli

This study was designed to compare the effectiveness of acidified sodium chlorite (ASC) and sodium hypochlorite (NaClO) in reducing several Escherichia coli strains isolated from different retail meat and fresh produce. Forty nonpathogenic E. coli strains were isolated and used in this study. A type strain of E. coli (JCM 1649) and four O157:H7 serotypes of E. coli (CR-3, MN-28, MY-29, and DT-66) were used as reference. In vitro assay results revealed that the viable cell counts of each isolated E. coli strain and control strains exhibited a reduction of similar to 4.3 +/- 0.9 log and 7.8 +/- 1.7 log CFU/mL after a 3-minute exposure to 100mg/L NaClO and 20mg/L ASC (pH 4.6), respectively, at 25 degrees C, when compared with the viable bacterial counts obtained from phosphate-buffered saline. The one exception was the flocs-forming strain, which showed a reduction of only 1.0 log CFU/mL with both disinfectants. However, reductions of only 1.7 +/- 0.3 log and 1.9 +/- 0.4 log CFU/g were observed in lettuce after 5 minutes of washing with NaClO and ASC, respectively. On the other hand, reductions of 1.6 +/- 0.2 log and 1.6 +/- 0.4 log CFU/g were observed in spinach after 5 minutes of washing with NaClO and ASC, respectively. No reduction in the population was observed after washing the inoculated, fresh-cut vegetables with distilled water only. No significant difference in the reduction of E. coli was observed among all the tested strains with both sanitizers in the in vivo assay. These data suggest that the tested sanitizers exhibit a similar reduction of the surface-attached E. coli on leafy vegetables irrespective of the strain source.