Altered sensitivity to a quaternary ammonium sanitizer in stressed Listeria innocua

Abstract

Chemical sanitizers are commonly used to inactivate Listeria monocytogenes and other Listeria species that persist in food-processing environments after cleaning. In this study, Listeria innocua cultures were exposed to acid, heat, cold, and starvation stress and then assessed for sensitivity to the quaternary ammonium compound cetrimide. Unstressed and stressed cultures were exposed to cetrimide for 3 min, neutralized, and plated on tryptic soy agar with yeast extract to determine the percentage of survivors. Relative to controls, L. innocua exposed to acid and starvation conditions was less sensitive to cetrimide, whereas heat and cold stress increased cetrimide sensitivity (P < 0.05). The diminished sensitivity of acid- and starvation-stressed L. innocua to cetrimide suggests that these stressors might increase the persistence of this organism within food-manufacturing facilities. In contrast, enhanced L. innocua sensitivity to cetrimide following heat and cold stress suggests that these interventions might increase sanitation efficacy. Copyright ©, International Association for Food Protection.