Validation of the detection of STEC (O26, O45, O103, O111, O121, O145 and O157) in raw burgers using real-time PCR (BAX® System Q7, DuPont) in “WET POOLS”

Abstract

Shiga toxin-producing Escherichia coli (STEC) O157:H7 and no-O157:H7 have been identified as emerging foodborne pathogens responsible for an increasing number of outbreaks worldwide. Many foods have been associated to these outbreaks, mainly undercooked beef burgers. Due to the increasing production and consumption of burgers in our country, it is important to have a rapid technique to identify and isolate the most important STEC strains in foods matrixes.The objective of these investigation was to assess the sensitivity, specificity and limit detection for the screening of the most prevalent STEC in frozen raw beef burgers, using the "STEC Screening stx/eae " kit to detect the stx/eae genes and the "Panel 1 STEC E. coli O26, O111, O121" and "Panel 2 STEC E. coli O45, O103, O145" and "E. coli O157: H7 MP” (DuPont) kits for the detection of the different serogroups. The use of composed samples (wet pools), the recovery of each strain from the positives samples on selective media after specified inmunoconcentration and the detection of stx/eae virulence genes in isolates by PCR were also evaluated. We validated a technique that allows the detection of the mentioned STEC strains with limits of detection between 1-5 CFU in 65 grams of raw frozen hamburgers, using wet pools. </p