CHAPITRE 1 - Université de Bourgogne

IMS sensitivity may also be affected by the bead-to-organism ratio used the enrichment broth,
and the problem of non-specific adsorption to the magnetic beads (which can be reduced by
the use of a low ionic strength solution in the IMS procedure and washing).Other studies have
evaluated the efficiency of IMS: the O26 and O111 IMS beads have been evaluated for the
detection of these STEC serogroups in vegetables (Safarikova and Safarik, 2001) and O103
IMS beads have been used to detect O103 serogroup in sheep faecal samples (Urdahl et al.,
2002). Safarikova and Safarik (2001) found that IMS increased the isolation of E. coli O26,
O103 and O111 in vegetables with 93-100% of samples positive by IMS compared to 36-93%
using direct culture.
Our study showed that the VIDAS ESPT can perform the immuno-concentration
automatically within 60 min for the five serogroups reported, with a maximum capacity of 30
samples in one run. In contrast, for the IMS method the concentration of 30 samples for one
serogroup takes about 100 min when using two magnetic particle concentrators, each fitted to
handle 6 samples at a time (Aminul Islam et al., 2006). Aminul Islam et al. (2006) found that
IMS method also has a potential risk for cross-contamination during the performance of
immunomagnetic separation. Compared with IMS method, the VIDAS ESPT are less time-
consuming and are fully automated and thus less labor intensive.
This study has demonstrated that the VIDAS ESPT is a promising tool to isolate E. coli O157,
O26, O103, O111 and O145 from food in a single assay, facilitates their subsequent
identification on selective agar plates.
This test could be used as a sample preparation in order to establish pathogenic status of
enrichment broth with a PCR assay. It would reduced the number of non-relevant PCR
positive results and so the number of confirmation. This automated method will provide
technical and economic advantages to the food industry for routine testing by reducing the
number of false positive PCR screen samples that need to be run through the confirmation
process. Works are underway in order to validate these data.
REFERENCES
Aminul Islam, M., A. E. Heuvelink, K. A. Talukder, and E. de Boer. 2006.
Immunoconcentration of Shiga toxin–producing Escherichia coli O157 from animal faeces
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