Effect of Stressors on the Viability of Listeria During an in vitro Cold-Smoking Process

Published 11/2012

volume 2 issue 3
Pp. 195-208 

Keywords: , , , , , , , , , ,

Abstract:

Listeria monocytogenes is a dangerous food-borne pathogen and is a frequent contaminant found in the cold-smoked fish industry. To identify strategies to eliminate this bacterium from the cold-smoking processing environment, it is imperative to understand how this microorganism tolerates the conditions en- countered. The aim of this study was to determine whether exposure to conditions likely to be encountered during the cold-smoking process differentially impacts various strains of Listeria monocytogenes and Liste- ria innocua. Viability of L. monocytogenes (EGDe, F2365, HCC7, ATCC 15313, and HCC23) and L. innocua in exponential or stationary growth phase were analyzed following a sequential exposure to conditions that mimic those utilized in the cold-smoking process: freeze (-20°C)-thaw (25°C), elevated salt, liquid smoke, and anaerobic storage (2°C). Viability for stationary phase cells exposed to the mock process decreased (P<0.05) for all strains except EGDe. Viability for exponential phase cells also decreased (P<0.05) for all strains except for EGDe and HCC7 treated cells. The cell envelope of the avirulent strain HCC23 was al- tered by all treatments examined, while the cell envelope of the virulent strain HCC7 was altered only after exposure to liquid smoke and anaerobic storage. Results indicate that both virulent and avirulent strains in this study, whether in exponential or stationary phase, can tolerate the conditions encountered during the cold-smoking process, and that virulent strains are more resistant than avirulent strains. Collectively, these data strongly suggest that differences exist in the mechanisms utilized by virulent and avirulent strains to adapt to conditions encountered in the cold-smoking process.


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