Influence of cold stress on the survival of Listeria monocytogenes Bug60 and ScottA in lethal alkali, acid and oxidative stress

Authors: ABEYSUNDARA, P - Mississippi State University; DHOWLAGHAR, N - Mississippi State University; NANNAPANENI, R - Mississippi State University

Submitted to: LWT - Food Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/5/2018
Publication Date: 2/1/2019
Citation: Abeysundara, P., Dhowlaghar, N., Nannapaneni, R. 2019. Influence of cold stress on the survival of Listeria monocytogenes Bug60 and ScottA in lethal alkali, acid and oxidative stress. LWT - Food Science and Technology. 100:40-47.

Interpretive Summary: L. monocytogenes is able to withstand adverse environmental conditions including temperature from 0 °C to 45 °C, pH from 4.1 to 9.6 and salt concentrations up to 20%. Particularly, the ability to survive and grow at low temperatures makes L. monocytogenes a serious food safety and public health risk. Despite frequent use of cleaners and sanitizers, the elimination of L. monocytogenes from food processing and storage environments is challenging since it may withstand in lethal alkali, acid, oxidative and chilled stress conditions that cells may experience during cleaning and sanitation. Understanding the role of cold stress on the survival of L. monocytogenes cells when subsequently exposed to acid, alkali and oxidative stress is important with respect to eliminating this foodborne pathogen. Moreover, most of the previous studies compared the survival of cold stress adapted and non-adapted L. monocytogenes cells by performing the time-to-kill studies in nutrient rich broth models (i.e. BHI or TSBYE). However, cells of L. monocytogenes are exposed to lethal disinfectants in water during the cleaning and sanitation process in food processing plant. The cross-protection effect of cold stress adapted cells to lethal disinfectants in water has not been published. Therefore, the objective of this study was to investigate the influence of cold stress (4 °C for 5 min to 24 h) on the survival of L. monocytogenes Bug600 and ScottA cells in lethal alkali, acid and oxidative stress conditions in TSBYE and distilled water. Our findings indicate acid based cleaners and sanitizers may be more effective at controlling cold stressed L. monocytogenes Bug600 and ScottA cells when compared to alkali or hydrogen peroxide-based cleaners and sanitizers.

Technical Abstract: The objective of this study was to determine the influence of cold stress (4°C) on the survival of Listeria monocytogenes Bug600 and ScottA in lethal alkali, acid and oxidative stress in tryptic soy broth containing yeast extract (TSBYE) and in distilled water. Four distinct patterns were observed for the survival of cold stressed cells of L. monocytogenes in lethal alkali, acid and oxidative stress: (1) Survival of L. monocytogenes was increased by 1-4 logs in lethal alkali stress (pH 12.3 NaOH or KOH) after cold stress at 4 °C for 1 h, 4 h or 24 h compared to non-cold stressed control cells; (2) Survival of L. monocytogenes was decreased by 1-4 logs in lethal acid stress (pH 1.3 HCl or H3PO4) after cold stress at 4 °C for 24 h compared to control; (3) Survival of L. monocytogenes was increased by 1-4 logs in lethal oxidative stress (1500 ppm H2O2) after cold stress at 4 °C for 4 h or 24 h compared to control; and (4) No difference in survival of L. monocytogenes was observed in lethal oxidative stress by chlorine (1000 ppm NaOCl) after cold stress at 4 °C for 24 h compared to control. These patterns were also consistently observed for survival of L. monocytogenes cells in lethal alkali, acid or oxidative stress after adaptation of cold stress at 4 °C in low nutrient conditions (1/10 TSBYE). These findings demonstrate that cold stressed cells of L. monocytogenes Bug600 and ScottA have greater tolerance to lethal alkali and some oxidative stresses that are commonly employed by the food industries to kill this foodborne pathogen.