Location: Meat Safety & Quality Research
Title: Chromogenic agar medium for detection and isolation of Escherichia coli serogroups O26,O45,O103,O111,O121, and O145 from fresh beef and cattle feces Authors
Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 6, 2012
Publication Date: February 1, 2013
Repository URL: http://handle.nal.usda.gov/10113/56093
Citation: Kalchayanand, N., Arthur, T.M., Bosilevac, J.M., Wells, J., Wheeler, T.L. 2013. Chromogenic agar medium for detection and isolation of Escherichia coli serogroups O26,O45,O103,O111,O121, and O145 from fresh beef and cattle feces. Journal of Food Protection. 76(2):192-199. Interpretive Summary: Although E.coli O157:H7 has received considerable attention in the U.S., non-O157 Shiga toxin-producing E. coli (STEC) strains are also known to cause severe illnesses. CDC reported that the top six serotypes of STEC accounted for 71% of cases in the U.S. However, STEC strains have not received the same level of attention due to a lack of unique characteristics to readily distinguish them from other E. coli strains. We developed a new agar medium that identifies the top six serogroups of STEC on one single agar plate. The agar significantly improved screening for the six serogroups of STEC.
Technical Abstract: Non-O157 Shiga toxin–producing Escherichia coli (STEC) strains are clinically important foodborne pathogens. Unlike E. coli O157:H7, these foodborne pathogens have no unique biochemical characteristics to readily distinguish them from other E. coli strains growing on plating media. In this study, a chromogenic agar medium was developed in order to differentiate among non-O157 STEC strains of serogroups O26, O45, O103, O111, O121, and O145 on a single agar medium. The ability of this chromogenic agar medium to select and distinguish among these pathogens is based on a combination of utilization of carbohydrates, b-galactosidase activity, and resistance to selective agents. The agar medium in combination with immunomagnetic separation was evaluated and successfully allowed for the detection and isolation of these six serogroups from artificially contaminated fresh beef. The agar medium in combination with immunomagnetic separation also allowed successful detection and isolation of naturally occurring non-O157 STEC strains present in cattle feces. Thirty-five strains of the top six non-O157 STEC serogroups were isolated from 1,897 fecal samples collected from 271 feedlot cattle. This chromogenic agar medium could help significantly in routine screening for the top six non-O157 STEC serogroups from beef cattle and other food.