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In vitro characterization of Shiga toxin-producing and generic Escherichia coli in respect of cheese-production relevant stresses


Peng, S; Stephan, R; Hummerjohann, J; Blanco, J; Zweifel, C (2012). In vitro characterization of Shiga toxin-producing and generic Escherichia coli in respect of cheese-production relevant stresses. Journal of Food Safety and Food Quality, 63(5):136-141.

Abstract

Forty-one Escherichia (E.) coli strains from raw milk cheese, including 26 Shiga toxin-producing strains (STEC), and six STEC strains from cattle feces were characterized in respect of cheese production-relevant stress (thermal inactivation, glucose-repressed oxidative acid resistance system, acidic and osmotic stress). Of all 47 E. coli isolates, seven generic E. coli strains showed an increased heat tolerance (55 °C, 15 min) and 20 strains (STEC and generic E. coli) exhibited a survival rate of ≥10 % (pH 2.5, 2 h) with induced oxidative acid resistance system. Besides, growth was observed for all E. coli strains at pH or aw values commonly found in (semi-hard) cheese (pH=5.2, aw=0.970), whereas counts tended to decrease at a pH value of 4.5 or an aW value of 0.942. Overall, no clear and universal differences between STEC and generic E. coli strains were found. The large strain variations observed in respect of the applied stresses within this strain collection do not indicate a shared feature amongst our E. coli strains that may be beneficial for their survival in raw milk cheese. It remains to be elucidated if there are key factors enabling the survival of E. coli and in particular STEC during production of raw milk cheese or if differences in the production process are more important.

Abstract

Forty-one Escherichia (E.) coli strains from raw milk cheese, including 26 Shiga toxin-producing strains (STEC), and six STEC strains from cattle feces were characterized in respect of cheese production-relevant stress (thermal inactivation, glucose-repressed oxidative acid resistance system, acidic and osmotic stress). Of all 47 E. coli isolates, seven generic E. coli strains showed an increased heat tolerance (55 °C, 15 min) and 20 strains (STEC and generic E. coli) exhibited a survival rate of ≥10 % (pH 2.5, 2 h) with induced oxidative acid resistance system. Besides, growth was observed for all E. coli strains at pH or aw values commonly found in (semi-hard) cheese (pH=5.2, aw=0.970), whereas counts tended to decrease at a pH value of 4.5 or an aW value of 0.942. Overall, no clear and universal differences between STEC and generic E. coli strains were found. The large strain variations observed in respect of the applied stresses within this strain collection do not indicate a shared feature amongst our E. coli strains that may be beneficial for their survival in raw milk cheese. It remains to be elucidated if there are key factors enabling the survival of E. coli and in particular STEC during production of raw milk cheese or if differences in the production process are more important.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:05 Vetsuisse Faculty > Institute of Food Safety and Hygiene
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
Language:English
Date:2012
Deposited On:11 Mar 2013 09:03
Last Modified:07 Dec 2017 20:23
Publisher DOI:https://doi.org/10.2376/0003-925X-63-136

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