Faster, Cheaper, More Accurate Detection of STEC

Background

STEC is a type of E. coli that produces Shiga toxin which causes foodborne illness in humans. STEC bacteria can be found in any undercooked or contaminated foods, but is mostly associated with beef. Because of its potential to cause severe disease, STEC is monitored by beef processors across Canada. Current joint media/PCR methods of testing make it easy to identify E. coli O157 and distinguish other STEC genes. However, most E. coli strains are not pathogenic and STEC genes can be found in other bacteria which makes it inefficient despite being widely adopted. Therefore, refining testing to only identify E. coli that are actively producing Shiga toxin would make sure only potentially harmful meat products would be removed from production which could save time, money, and effort.

A new media called “Stx media” by bioMerieux only identifies STEC. While already being tested by the USDA, Canada has unique strains, and processing conditions which stresses the need to test is this media under Canadian conditions to evaluate if it could be the future for STEC testing in Canadian beef processing plants.

Objectives

•  To simplify and reduce costs for monitoring Shiga toxin producing E. coli (STEC) in a way that meets current standards set for Canadian beef and improves food safety.

What they will do

 Fecal samples collected from a Lethbridge feedlot through concurrent study done by Dr. Tim McAllister will be mixed with a broth and incubated to encourage the growth of STEC bacteria. The Stx media will be used to plate samples of the broth and identified colonies of STEC will be further processed through PCR to identify virulence factor and serogroup. Virulence factors stx1 and stx2 will be assessed specifically, as these are consistently present in human outbreaks of E. coli infection.

The original fecal broth will also have DNA extracted for PCR detection of the same virulence factors and serogroup using traditional testing methods. This will allow the team to compare the ability of each method (Stx media and traditional media/PCR) to identify samples contaminated with STEC.    

Implications

This POC study should be able to demonstrate if Stx media has the ability to reduce costs, time, and effort required to monitor STEC at beef processing plants. Not only would this more efficient and reliable test improve food safety and potentially reduce the cost of beef to the consumer, but it could also provide a more stable market for international trade, especially to the United States.