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ARS Home » Northeast Area » Wyndmoor, Pennsylvania » Eastern Regional Research Center » Microbial and Chemical Food Safety » Research » Publications at this Location » Publication #320027
Title: Effects of stresses on the growth and Cytotoxicity of Shiga-Toxin producing Escherichia coli in ground beef and spinach

Author
item Yoo, Byong
item Liu, Yanhong
item Juneja, Vijay
item Huang, Lihan
item Hwang, Cheng An

Submitted to: Journal of Food Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/23/2015
Publication Date: 1/1/2016
Citation: Yoo, B.K., Liu, Y., Juneja, V.K., Huang, L., Hwang, C. 2016. Effects of stresses on the growth and Cytotoxicity of Shiga-Toxin producing Escherichia coli in ground beef and spinach. Journal of Food Science and Technology. 1:1-7.

Interpretive Summary: Strains of Shiga-toxin producing Escherichia coli (STEC) have been implicated in outbreaks of foodborne illnesses linked to the consumption of ground beef and spinach. This study examined the effect of chlorine, water activity, acid, and starvation stresses on the growth and cytotoxicity of STEC in ground beef and spinach. Results showed starvation and chlorine stresses induced higher growth of non-O157 than O157, and stressed O157 and non-O157 STEC exhibited higher cytotoxicity in ground beef and spinach. The findings illustrate the importance of applying suitable control measures to eliminate the presence of stressed STEC in beef and spinach processing environment and their subsequent contamination in the products.

Technical Abstract: The objectives of this study were to examine the effect of stresses on the growth and cytotoxicity of pathogenic Escherichia coli in beef and spinach. A mixture of three strains of Shiga toxin-producing E. coli (STEC) O157:H7 or four strains of non-O157 STEC O26:H11, O103:H1, O104:H4, and O145:NM was subjected to stresses of 2 ppm chlorine, aw 0.97, pH 5, or 15-day starvation. Stressed or non-stressed STEC was inoculated into 5 g of irradiated ground beef or spinach. The cell populations during storage at 8, 12, or 16 degrees Celsius for 4 weeks were compared to evaluate the effects of stresses on the growth. Supernatant from each sample after 24-h incubation at 22 degree C was used to determine the Vero-cytotoxicity. At 8 degrees Celsius, the population of non-O157 was higher than O157 in ground beef after 4 weeks. However, in spinach, the populations after 4 weeks at 8 degrees Celsius were not different. Starvation and chlorine stresses induced higher growth of non-O157 than O157 in ground beef and spinach. Cytotoxicity assay showed that stressed O157 and non-O157 STEC exhibited higher cytotoxicity than the non-stressed controls. Results showed that multiple exposures to sub-lethal stresses enhanced the cytotoxicity of STEC in both ground beef and spinach. The findings illustrate the importance of applying suitable control measures to eliminate the presence of stressed STEC in beef and spinach processing environment and their subsequent contamination in the products.