Enhanced protection of pathogenic Escherichia coli ingested by a soil nematode Caenorhabditis elegans against sanitizer treatments

We employed Caenorhabditis elegans as a model to study the effectiveness of sanitizers in killing pathogenic Escherichia coli strains ingested by free-living nematodes. Adult worms that had fed on six pathogenic E. coli strains (highly persistent in the nematode intestine) were treated with three chemical solutions. In planktonic cells, none of the H₂O₂ and acetic acid treatments influenced the survival of the pathogenic E. coli strains, whereas sodium hypochlorite critically decreased the viability of the strains. Importantly, the survival of the E. coli strains was dramatically increased by persistence in the C. elegans gut under 0.1% sodium hypochlorite, and several strains could survive at a concentration of 0.5%. In addition, all pathogenic E. coli strains in the C. elegans gut survived on the lettuce for 5 days even though they were washed with 0.1% sodium hypochlorite. Taken together, our results indicate that pathogenic E. coli ingested by C. elegans may be protected against washing treatment with commercial sanitizers on raw food materials.