Evaluation of the efficacy of commercial sanitizers against adhered and planktonic cells of Listeria monocytogenes and Salmonella spp.

Antimicrobial activities of two commercial disinfectants, alone or combined with heat, against three Salmonella strains and three Listeria monocytogenes strains were studied. The efficacy of disinfectants against planktonic bacteria and bacteria attached to three food contact industrial surfaces (stainless steel, polytetraflourethylene, and rubber) was investigated. The tests were conducted using the sanitizer (quaternary ammonium compounds, and alquyldiethylenediamineglycine and di-alquyldiamineethylglycine) concentrations recommended by the manufacturers, and concentrations twice and four times higher than those values. The recommended concentrations were not effective to kill bacteria, especially when they were attached to surfaces. Concentrations of disinfectants twice and four times higher than those recommended were needed to fully eliminate planktonic bacteria. These same sanitizer concentrations were not sufficient to remove attached bacteria. To remove them from the surfaces, a treatment with recommended concentrations in combination with heat was needed. Our results indicate that these two pathogenic bacteria could survive common sanitation programs used in the food industry