|He, Shoukui - Shanghai Jiaotong University|
|Cui, Yan - Shanghai Jiaotong University|
|Zhang, Fen - Shanghai Jiaotong University|
|Shi, Chunlei - Shanghai Jiaotong University|
|Shi, Xianming - Shanghai Jiaotong University|
Submitted to: Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/7/2017
Publication Date: 2/23/2018
Citation: He, S., Cui, Y., Zhang, F., Shi, C., Paoli, G., Shi, X. 2018. Influence of ethanol adaptation on Salmonella enterica serovar Enteritidis survival in acidic environments and expression of acid tolerance-related genes. Food Microbiology. 72:193-198.
DOI: https://doi.org/10.1016/j.fm.2017.12.005 Interpretive Summary: Food preservation methods create stressful conditions for spoilage and disease-causing (pathogenic) bacteria reducing their growth to extend shelf life and increase food safety. When exposed to a stressful condition, foodborne bacteria can increase their resistance to subsequent stresses. In this study the adaptive response of the foodborne pathogen Salmonella after exposure to alcohol was studied. Exposure of alcohol-adapted Salmonella to freezing (-4 deg F), refrigeration (39 deg F), heat (130 deg F), high salt, or an otherwise lethal concentration of alcohol revealed that pre-exposure to sub-lethal concentrations of alcohol increased Salmonella’s resistance to freezing or a subsequent challenge with alcohol. The results are valuable in developing adequate and efficient control measures for S. Enteritidis in foods.
Technical Abstract: Aims: Salmonella enterica serovar Enteritidis (S. Enteritidis) can encounter mild ethanol stress during its life cycle. However, adaptation to a stressful condition may affect bacterial resistance to subsequent stresses. Hence, this work was undertaken to investigate the influences of ethanol adaptation on stress tolerance of S. Enteritidis. Methods and Results: S. Enteritidis was subjected to different ethanol adaptation treatments (2.5-10% ethanol for 1 h). Cellular morphology and tolerance to subsequent environmental stresses (15% ethanol, -20 deg C, 4 deg C, 55 deg C and 10% NaCl) were evaluated. It was found that 10% was the maximum ethanol concentration that allowed growth of S. Enteritidis. Ethanol adaptation did not cause cell-surface damage in S. Enteritidis as revealed by electron micrograph analysis. Ethanol-adapted S. Enteritidis displayed an enhanced resistance to a 15%-ethanol challenge compared with an unchallenged control. The maximum ethanol resistance was observed in S. Enteritidis adapted with 5.0%, 7.5% and 10% ethanol. Additionally, pre-adaptation to 5.0% ethanol cross-protected S. Enteritidis against a temperature challenge of -20 deg C, but not 4 deg C, 55 deg C or 10% NaCl. Conclusions: Ethanol adaptation provided S. Enteritidis direct protection from a high level ethanol challenge and cross protection from freezing, but not other stresses tested. Significance and Impact of the Study: The results are valuable in developing adequate and efficient control measures for S. Enteritidis in foods.