CHAPITRE 1 - Université de Bourgogne
CHAPITRE 1 - Université de Bourgogne
CHAPITRE 1 - Université de Bourgogne
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E. coli<br />
strains<br />
O26<br />
O103<br />
O111<br />
O145<br />
O157<br />
Methods<br />
10 5<br />
Dilutions (CFU/mL)<br />
10 4<br />
10 3<br />
VIDAS ESPT + + + -<br />
IMS + + + -<br />
VIDAS ESPT + + + -<br />
IMS + + + -<br />
VIDAS ESPT + + - -<br />
IMS + + - -<br />
VIDAS ESPT + + - -<br />
IMS + - - -<br />
VIDAS ESPT + + + -<br />
IMS + + - -<br />
+: all tested strains were found on the isolation media<br />
- : at least one of the strains was not found on the isolation media<br />
The assay performed on artificially inoculated samples (1 to 5 CFU/25g) followed by<br />
enrichment showed high sensitivity for the isolation of STEC strains both the VIDAS ESPT<br />
and IMS methods. Five strains of each serogroup were tested and all were isolated after<br />
VIDAS ESPT and IMS methods. Compared to traditional IMS plates, VIDAS ESPT method<br />
gave less background flora. VIDAS ESPT automated method greatly facilitated the recovery<br />
of serogroups of interest.<br />
DISCUSSION<br />
Escherichia coli O157:H7 is the predominant and most virulent serotype of STEC.<br />
Nevertheless, other non-O157 serogroups, including O26, O103, O111 and O145 have been<br />
associated with occasional outbreaks human disease or sporadic cases. Sensitive and rapid<br />
<strong>de</strong>tection methods for these five serogroups are essential for the food industry to ensure a safe<br />
food supply.<br />
Diagnostic procedure for STEC has been <strong>de</strong>veloped primarily for E. coli O157:H7. All<br />
existing validated methods research this serogroup. Detection of non-O157 STEC relies on<br />
direct analysis of colonies on plates of limited selectivity or by immunoblotting or DNA<br />
probing. Immuno magnetic separation (IMS) is used for selective concentration of serogroups<br />
O26, O103, O111, O145 and O157 from pre-enriched samples to assist in plate isolation.<br />
The VIDAS ESPT is a new method, allowing immuno-concentration of the “gang of five”<br />
simultaneously using a new technology of phage recombinant protein. This specificity of<br />
phage is the result of billions of years of evolutionary pressure between the phage and the host<br />
10 2<br />
139