The fate of Escherichia coli O157:H7 when exposed to sublethal and lethal concentrations of common industrial sanitizers

This study tested the hypothesis that pre-exposure of Escherichia coli O157:117 to sub-lethal levels of industrial sanitizers could affect the survival of cells to subsequent exposure at lethal levels. The susceptibility of planktonic and adherent cells to sanitizing compounds was compared. The ability for an acid tolerant Escherichia coli O157:117 strain to provide cross-protection to the cells when exposed to chemical sanitizers was also examined.; E. coli O157:117 cells were exposed to a chlorine compound, an iodophor, a quaternary ammonium compound (quat) and a peroxyacetic acid compound (PAA). Results show that at the concentrations utilized in this study, the iodophor provided the greatest reduction in planktonic cells followed by chlorine, then quat and the PAA compound. All sanitizers, except the peroxyacetic acid, were effective (greater than 5 log reduction) against the planktonic Escherichia coli O157:117 bacterial isolates. Data from the planktonic stage of testing showed that lack of recovery by plate count method after sanitizer treatment did not mean that an organism was no longer present. Both strains demonstrated the ability to recover and grow in broth after treatment with all of the sanitizers.; All sanitizers tested were significantly less effective against the adherent cells than the planktonic cells. The iodophor compound was the only sanitizer found to be effective against both planktonic and adherent cells. Neither the chlorine compound nor the PAA compound was effective against the adherent cells. The quaternary ammonium compound was only effective against the acid tolerant strain for adherent cells.; Throughout testing, the un-adapted Escherichia coli O157:117 strain typically showed higher survival rates than the known acid tolerant strain. Additionally, with one exception, the bacterial cells that exhibited an increased minimum inhibitory concentration did not demonstrate any increased resistance when exposed to other sanitizers.; While the pretreatment of bacterial cells with a quaternary ammonium and a peroxyacetic acid compound resulted in survival at higher concentrations, the values were still far below the recommended usage level. This adaptation does however demonstrate the importance of proper cleaning and sanitation procedures to ensure a safe product.