Analysis of Sanitizer Rotation on the Susceptibility, Biofilm Forming Ability and Caco-2 Cell Adhesion and Invasion of Listeria .

The purpose of this study was to determine the effect of sanitizer use conditions on the susceptibility, biofilm forming ability and pathogenicity of Listeria   monocytogenes . Two different strains of L. monocytogenes and a non-pathogenic L. innocua were exposed to sodium hypochlorite, benzalkonium chloride and peroxyacetic acid at different concentrations (4 to 512 ppm) and treatment times (30 s to 5 min), respectively. Under the tested conditions, no significant difference ( p > 0.05) in reduction was observed among the three tested sanitizers. A reduction of 1 to 8 log CFU/mL was observed depending upon the sanitizer concentration and treatment times. The survived cells at the highest sublethal concentration and treatment time of a particular sanitizer upon re-exposure to the same or different sanitizer showed either no change or increased susceptibility when compared to parent strains. Upon repeated exposure to sanitizers at progressively increasing concentrations from 1 to 128 ppm, L. innocua was able to survive concentrations of up to 32 ppm benzalkonium chloride and 64 ppm peroxyacetic acid treatments, respectively. At the tested sub-lethal concentrations, no significant difference ( p > 0.05) in biofilm formation was observed among the tested strains. Caco-2 interaction with L. innocua showed a reduction in invasion ability with sublethal concentrations of sanitizers.