Dynamics of Physiological Changes of Shiga Toxin-Producing <i>Escherichia coli</i> O157:H7 on Romaine Lettuce During Pre-Processing Cold Storage, and Subsequent Effects on Virulence and Stress Tolerance

If lettuce is contaminated in the field, Shiga toxin-producing <i>E. coli</i> (STEC) O157:H7 can survive through the distribution chain. Prolonged cold storage during transportation may impact pathogen physiology, affecting subsequent stress survival and virulence. Greenhouse-grown Romai...

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Main Authors: Dimple Sharma, Joshua O. Owade, Corrine J. Kamphuis, Avery Evans, E. Shaney Rump, Cleary Catur, Jade Mitchell, Teresa M. Bergholz
Format: Article
Language:English
Published: MDPI AG 2025-05-01
Series:Applied Microbiology
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Online Access:https://www.mdpi.com/2673-8007/5/2/45
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author Dimple Sharma
Joshua O. Owade
Corrine J. Kamphuis
Avery Evans
E. Shaney Rump
Cleary Catur
Jade Mitchell
Teresa M. Bergholz
author_facet Dimple Sharma
Joshua O. Owade
Corrine J. Kamphuis
Avery Evans
E. Shaney Rump
Cleary Catur
Jade Mitchell
Teresa M. Bergholz
author_sort Dimple Sharma
collection DOAJ
description If lettuce is contaminated in the field, Shiga toxin-producing <i>E. coli</i> (STEC) O157:H7 can survive through the distribution chain. Prolonged cold storage during transportation may impact pathogen physiology, affecting subsequent stress survival and virulence. Greenhouse-grown Romaine lettuce, inoculated with three STEC O157:H7 strains, was harvested after 24 h and stored at 2 °C for 5 d following 4 h at harvest temperature (9 °C or 17 °C). Culturable, persister, and viable but non-culturable (VBNC) cells were quantified. Virulence was evaluated using <i>Galleria mellonella</i> and acid tolerance at pH 2.5 and tolerance to 20–25 ppm free chlorine were quantified. Colder harvest temperature (9 °C) before cold storage led to greater transformation of STEC O157:H7 into dormant states and decreased virulence in most cases. Increasing length of cold storage led to decreased virulence and acid tolerance of STEC O157:H7 on lettuce, while having no significant effect on chlorine tolerance. These findings highlight that entry of STEC O157:H7 into dormant states during harvest and transportation at cold temperatures leads to decreased stress tolerance and virulence with increasing cold storage. Changes in STEC O157:H7 physiology on lettuce during cold storage can be integrated into risk assessment tools for producers, which can assist in identifying practices that minimize risk of STEC O157:H7 from consumption of lettuce.
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spelling doaj-art-c3da7dfc3ec14bcbb79f9bc608b4bfe52025-08-20T03:32:28ZengMDPI AGApplied Microbiology2673-80072025-05-01524510.3390/applmicrobiol5020045Dynamics of Physiological Changes of Shiga Toxin-Producing <i>Escherichia coli</i> O157:H7 on Romaine Lettuce During Pre-Processing Cold Storage, and Subsequent Effects on Virulence and Stress ToleranceDimple Sharma0Joshua O. Owade1Corrine J. Kamphuis2Avery Evans3E. Shaney Rump4Cleary Catur5Jade Mitchell6Teresa M. Bergholz7Department of Food Science and Human Nutrition, Michigan State University, East Lansing, MI 48224, USADepartment of Biosystems and Agricultural Engineering, Michigan State University, East Lansing, MI 48224, USADepartment of Food Science and Human Nutrition, Michigan State University, East Lansing, MI 48224, USADepartment of Food Science and Human Nutrition, Michigan State University, East Lansing, MI 48224, USADepartment of Food Science and Human Nutrition, Michigan State University, East Lansing, MI 48224, USADepartment of Food Science and Human Nutrition, Michigan State University, East Lansing, MI 48224, USADepartment of Biosystems and Agricultural Engineering, Michigan State University, East Lansing, MI 48224, USADepartment of Food Science and Human Nutrition, Michigan State University, East Lansing, MI 48224, USAIf lettuce is contaminated in the field, Shiga toxin-producing <i>E. coli</i> (STEC) O157:H7 can survive through the distribution chain. Prolonged cold storage during transportation may impact pathogen physiology, affecting subsequent stress survival and virulence. Greenhouse-grown Romaine lettuce, inoculated with three STEC O157:H7 strains, was harvested after 24 h and stored at 2 °C for 5 d following 4 h at harvest temperature (9 °C or 17 °C). Culturable, persister, and viable but non-culturable (VBNC) cells were quantified. Virulence was evaluated using <i>Galleria mellonella</i> and acid tolerance at pH 2.5 and tolerance to 20–25 ppm free chlorine were quantified. Colder harvest temperature (9 °C) before cold storage led to greater transformation of STEC O157:H7 into dormant states and decreased virulence in most cases. Increasing length of cold storage led to decreased virulence and acid tolerance of STEC O157:H7 on lettuce, while having no significant effect on chlorine tolerance. These findings highlight that entry of STEC O157:H7 into dormant states during harvest and transportation at cold temperatures leads to decreased stress tolerance and virulence with increasing cold storage. Changes in STEC O157:H7 physiology on lettuce during cold storage can be integrated into risk assessment tools for producers, which can assist in identifying practices that minimize risk of STEC O157:H7 from consumption of lettuce.https://www.mdpi.com/2673-8007/5/2/45persisterVBNCchlorinelow pHlow temperature<i>Galleria mellonella</i>
spellingShingle Dimple Sharma
Joshua O. Owade
Corrine J. Kamphuis
Avery Evans
E. Shaney Rump
Cleary Catur
Jade Mitchell
Teresa M. Bergholz
Dynamics of Physiological Changes of Shiga Toxin-Producing <i>Escherichia coli</i> O157:H7 on Romaine Lettuce During Pre-Processing Cold Storage, and Subsequent Effects on Virulence and Stress Tolerance
Applied Microbiology
persister
VBNC
chlorine
low pH
low temperature
<i>Galleria mellonella</i>
title Dynamics of Physiological Changes of Shiga Toxin-Producing <i>Escherichia coli</i> O157:H7 on Romaine Lettuce During Pre-Processing Cold Storage, and Subsequent Effects on Virulence and Stress Tolerance
title_full Dynamics of Physiological Changes of Shiga Toxin-Producing <i>Escherichia coli</i> O157:H7 on Romaine Lettuce During Pre-Processing Cold Storage, and Subsequent Effects on Virulence and Stress Tolerance
title_fullStr Dynamics of Physiological Changes of Shiga Toxin-Producing <i>Escherichia coli</i> O157:H7 on Romaine Lettuce During Pre-Processing Cold Storage, and Subsequent Effects on Virulence and Stress Tolerance
title_full_unstemmed Dynamics of Physiological Changes of Shiga Toxin-Producing <i>Escherichia coli</i> O157:H7 on Romaine Lettuce During Pre-Processing Cold Storage, and Subsequent Effects on Virulence and Stress Tolerance
title_short Dynamics of Physiological Changes of Shiga Toxin-Producing <i>Escherichia coli</i> O157:H7 on Romaine Lettuce During Pre-Processing Cold Storage, and Subsequent Effects on Virulence and Stress Tolerance
title_sort dynamics of physiological changes of shiga toxin producing i escherichia coli i o157 h7 on romaine lettuce during pre processing cold storage and subsequent effects on virulence and stress tolerance
topic persister
VBNC
chlorine
low pH
low temperature
<i>Galleria mellonella</i>
url https://www.mdpi.com/2673-8007/5/2/45
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