P3-147 Role of Extra-cellular Cellulose Production on the Survival of Shiga Toxin-producing Escherichia coli on Lettuce and Spinach after Chlorine Treatment

Wednesday, July 31, 2013
Exhibit Hall (Charlotte Convention Center)
Chi-Ching Lee, University of Georgia, Athens, GA
Jinru Chen, The University of Georgia, Griffin, GA
Joseph Frank, University of Georgia, Athens, GA
Introduction: Chlorinated water with maximum allowable level 200 ppm of chlorine is widely used to sanitize fresh-cut produce on an industrial scale. Shiga toxin–producing Escherichia coli (STEC) produce extra-cellular cellulose which may influence stress tolerance. 

Purpose: This study was undertaken to investigate the role of extra-cellular cellulose produced by STEC on the survival of STEC after attachment to lettuce and spinach followed by chlorine treatment.

Methods: Four STEC strains, two wild-type cellulose-producing and their cellulose-deficient derivates, were used. One strain produced colanic acid in addition to cellulose. Leaves of spinach and lettuce were treated with chlorinated water (50 and 150 ppm) after cells were attached to the surface and cut edge of lettuce at 4°C for 2 hours.

Results: Chlorine treatment reduced the population of cellulose-deficient cells at 1 log units more than the wild type in 150 ppm of chlorine on spinach leaves surface. However, the population of cellulose-producing cells was reduced by 1 log units more than its mutant when cells can also produce colanic acid. There were no significant differences in survival between four strains attached at the cut edge.

Significance: Extra-cellular cellulose production protects STEC cells attached to leafy greens from the effects of chlorine on spinach leave surface.