Presence of Shiga toxin-producing Escherichia coli O-groups in small and very-small beef-processing plants and resulting ground beef detected by a multiplex polymerase chain reaction assay.

Shiga toxin-producing Escherichia coli (STEC) are associated with foodborne illnesses, including hemolytic uremic syndrome in humans. Cattle and consequently, beef products are considered a major source of STEC. E. coli O157:H7 has been regulated as an adulterant in ground beef since 1996. The United States Department of Agriculture Food Safety and Inspection Service began regulating six additional STEC (O145, O121, O111, O103, O45, and O26) as adulterants in beef trim and raw ground beef in June 2012. Little is known about the presence of STEC in small and very-small beef-processing plants. Therefore, we propose to determine whether small and very-small beef-processing plants are a potential source of non-O157:H7 STEC. Environmental swabs, carcass swabs, hide swabs, and ground beef from eight small and very-small beef-processing plants were obtained from October 2010 to December 2011. A multiplex polymerase chain reaction assay was used to determine the presence of STEC O-groups: O157, O145, O121, O113, O111, O103, O45, and O26 in the samples. Results demonstrated that 56.6% (154/272) of the environmental samples, 35.0% (71/203) of the carcass samples, 85.2% (23/27) of the hide samples, and 17.0% (20/118) of the ground beef samples tested positive for one or more of the serogroups. However, only 7.4% (20/272) of the environmental samples, 4.4% (9/203) of the carcass samples, and 0% (0/118) ground beef samples tested positive for both the serogroup and Shiga toxin genes. Based on this survey, small and very-small beef processors may be a source of non-O157:H7 STEC. The information from this study may be of interest to regulatory officials, researchers, public health personnel, and the beef industry that are interested in the presence of these pathogens in the beef supply.