Agroscope Institute for Food science

Bern, Switzerland

Agroscope Institute for Food science

Bern, Switzerland
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Peng S.,University of Zürich | Peng S.,Agroscope Institute for Food science | Stephan R.,University of Zürich | Hummerjohann J.,Agroscope Institute for Food science | Tasara T.,University of Zürich
FEMS Microbiology Letters | Year: 2014

Survival of Escherichia coli in food depends on its ability to adapt against encountered stress typically involving induction of stress response genes. In this study, the transcriptional induction of selected acid (cadA, speF) and salt (kdpA, proP, proW, otsA, betA) stress response genes was investigated among five E. coli strains, including three Shiga toxin-producing strains, exposed to sodium chloride or lactic acid stress. Transcriptional induction upon lactic acid stress exposure was similar in all but one E. coli strain, which lacked the lysine decarboxylase gene cadA. In response to sodium chloride stress exposure, proW and otsA were similarly induced, while significant differences were observed between the E. coli strains in induction of kdpA, proP and betA. The kdpA and betA genes were significantly induced in four and three strains, respectively, whereas one strain did not induce these genes. The proP gene was only induced in two E. coli strains. Interestingly, transcriptional induction differences in response to sodium chloride stress exposure were associated with survival phenotypes observed for the E. coli strains in cheese as the E. coli strain lacking significant induction in three salt stress response genes investigated also survived poorly compared to the other E. coli strains in cheese. © 2014 Federation of European Microbiological Societies.


Peng S.,University of Zürich | Peng S.,Agroscope Institute for Food science | Weik D.,Agroscope Institute for Food science | Stephan R.,University of Zürich | Hummerjohann J.,Agroscope Institute for Food science
Archiv fur Lebensmittelhygiene | Year: 2015

In order to survive cheese production and cheese ripening Escherichia coli needs to adapt to the encountered stress such as the raised salt concentrations. Such adaptation typically involves the induction of stress response genes. Therefore, impaired or lacking activity in such genes may considerably affect survival of E. coli upon stress exposure such as encountered during cheese production. In previous in vitro studies, an association between E. coli stress response gene expression and survival observed in raw milk cheese was found, indicating that reduced or absent induction of the salt stress response gene kdpA might have an impact on survival of an E. coli strain during raw milk cheese production. In this study, therefore, the survival of an E. coli strain deleted in the kdpA gene was investigated in comparison to its wild- Type strain during production and ripening of semi-hard cheese. After an initial increase in E. coli counts a slow decrease of 1.80 and 1.38 log10 cfu/g until the end of the 16 week ripening period was observed for the /cdp,4-deletion and the wild-type strain, respectively, without significant differences between these strains. This indicates that lack of the kdpA gene did not considerably affect E. coli survival in cheese and therefore other stress response mechanisms are probably of higher importance for survival of E. coli in raw milk cheese.


Thanner S.,Agroscope Institute for Livestock science | Drissner D.,Agroscope Institute for Food science | Walsh F.,National University of Ireland
mBio | Year: 2016

In this article, the current knowledge and knowledge gaps in the emergence and spread of antimicrobial resistance (AMR) in livestock and plants and importance in terms of animal and human health are discussed. Some recommendations are provided for generation of the data required in order to develop risk assessments for AMR within agriculture and for risks through the food chain to animals and humans. © 2016 Thanner et al.

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