Shiga Toxin-Producing Escherichia coli: Detection, Differentiation, and Implications for Food Safety

Figure 1. STEC isolation from various selective media. (A) Cells from enrichment broth are plated on CT-SMAC. (B) Suspect colonies appear as pale on CT-SMAC and steel blue on NT-Rainbow Media, and non-O157 STECs appear as pink colonies on NT-Rainbow (C) Suspect STECS expressing b-galactosidase and hemolysin are indicated by blue colonies with a zone of clearing on Sheeps blood agar (D) Typical non-O157 STECs are shown growing on CHROMagar and appear as blue colonies. Credits: Mike Cooley
Shiga toxin is a protein found within the genome of a type of virus called a bacteriophage. These bacteriophages can integrate into the genomes of the bacterium E. Coli. Even though most E. coli are benign or even beneficial members of our gut microbial communities, strains carrying Shiga-toxin encoding genes are highly pathogenic in humans and other animals. This six-page fact sheet discusses the two types of Shiga toxins and the best approaches to identifying and determining which Shiga toxin is present. Written by William J. Zaragoza, Max Teplitski, and Clifton K. Fagerquist and published by the Department of Soil and Water Sciences.