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Establishment of Non-O157 Shiga-toxin Producing E. coli (STEC) Baseline in Raw Ground Beef in the US

Investigators
Loneragan, Guy; Brashears, Mindy
Institutions
Texas Tech University
Start date
2011
End date
2012
Objective
Shiga toxin-producing Escherichia coli (STEC), which are capable of producing Shiga toxin 1 and/or 2, have been associated with foodborne outbreaks and caused severe human illness such as bloody diarrhea, hemolytic uremic syndrome (HUS), and kidney failure, since 1982 when E. coli O157:H7 was frequently isolated from the undercooked hamburger beef patties. Although not all non-O157 STEC are pathogenic to humans, some non-O157 STEC strains have been related to sporadic cases of human illness, and are able to cause disease as severe as E. coli O157:H7, such as bloody diarrhea, hemorrhagic colitis, HUS or even death. STEC primarily resides in the gastrointestinal tract of ruminants, especially cattle, and will not cause any illness to their hosts. These strains can be easily disseminated to the environment or other surfaces through direct fecal contamination, which is also the primary food safety issue during the production of beef products. Centers for Disease Control and Prevention (CDC) estimated that six non-O157 STEC strains, including serotypes O26, O45, O103, O111, O121, and O145, accounted for over 70% of non-O157 STEC outbreaks in the United States. Due to the increasing number of non-O157 STEC-associated illness and capability of developing severe disease, USDA’s Food Safety and Inspection Service (FSIS) has declared the six most prevalent non-O157 STEC (O26, O45, O103, O111, O121, and O145) as adulterants in ground beef or other non-intact beef products.

Due to non-phenotypic characteristics of non-O157 STEC, it has been a challenge to detect these bacteria with the fast and accurate methods; therefore, illness associated with non-O157 STEC has always been under-estimated. Polymerase chain reaction (PCR)-based detection methods have been considered as valuable tools to trace outbreaks of bacterial pathogens in the food supplies. The BAX system is one of the commercial PCR-based systems that utilize the amplification of a specific target DNA sequence for the detection of pathogens in the food.

To date, unlike E. coli O157:H7, the information regarding the prevalence of non-O157 STEC in commercial ground beef samples from the retailers is scarce. Therefore, there is a need to set up the baseline of non-O157 STEC in the commercial ground beef samples and to determine fast and reliable methods to detect those stains.

The objective of this study was to identify the prevalence of the six pathogenic non-O157 STECs (serotypes O26, O45, O103, O111, O121, O145) in commercial ground beef products, and their association with different harvest parts from carcass, and lean/fat proportion.

More information
The results of this study indicated that the prevalence of non-O157 STEC were 0.9% in the ground beef samples. Additionally, ground beef made of different part of meat from the carcass, such as round, chuck or sirloin, wasn’t related to the detection of the non-O157 STEC; however, non-O157 STECs were most frequently isolated from the 85/15 (lean/fat) portion of ground beef products. The most common O groups detected were O26 (n=4), followed by O103 (n=3), O45 (n=2), O145 (n=2), and O121 (n=1). The overall prevalence of nonO157 in this study was less than 15 indicating it is not commonly found in retail beef samples.

For complete projects details, view the Project Summary.

Funding Source
Nat'l. Cattlemen's Beef Assoc.
Project source
View this project
Project number
BC-2011-4
Categories
Escherichia coli
Bacterial Pathogens
Parasites