Purpose: The objectives of this study were to determine the relative sensitivity and specificity of VIDAS-ICE, VIDAS-UP, real-time PCR, and immunomagnetic E. coli O157 detection methods.
Methods: E. coli O157 detection limits in artificially contaminated beef and cattle faeces samples enriched in either modified tryptone soya broth with novobiocin (mTSB+n) or buffered peptone water (BPW) were determined for Dynabeads anti E. coli O157 immunomagnetic beads, VIDAS-ICE, VIDAS-UP and real-time PCR (GeneDisc and LightCycler) systems.
Results: Dynabeads anti- E. coli O157 immunomagnetic separation (IMS) and the GeneDisc cycler were the most sensitive methods, and could detect an initial 1 CFU in beef samples after 6h of incubation in mTSB+n or BPW. The VIDAS-UP method could detect an initial 10 CFU, while VIDAS-ICE and the LightCycler methods could only detect an initial 100 CFU. Higher detection rates were achieved with 18 hour incubations, where an initial 1 CFU could be detected with all five methods. For cattle faeces enrichments, Dynabeads anti E. coli O157 IMS could detect an initial 1 CFU after a 6h incubation in mTSB+n, while the VIDAS-UP and VIDAS-ICE methods could detect an initial 10 CFU and both PCR methods could only detect an initial 100 CFU. Detection rates were lower in BPW, compared to mTSB+n, with thresholds of 100 CFU for VIDAS-ICE, VIDAS-UP and GeneDisc methods, and >100 CFU for the LightCycler method.
Significance: GeneDisc, and VIDAS-UP E. coli O157 detection methods can be used as rapid screening methods before final confirmation on selective agar as the two methods showed high sensitivity and specificity for E. coli O157 which is complemented by high levels of automation and relative ease of use.