CHAPITRE 1 - Université de Bourgogne
CHAPITRE 1 - Université de Bourgogne
CHAPITRE 1 - Université de Bourgogne
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Strains<br />
Number<br />
tested<br />
Detected after<br />
VIDAS ESPT<br />
E. coli O26 10 10<br />
E. coli O103 10 10<br />
E. coli O111 4 4<br />
E. coli O145 7 7<br />
E. coli O157 10 10<br />
Others (Citrobacter, E.<br />
coli, Staphylococcus …)<br />
11 2<br />
The sensitivity study performed on the dilutions of pure cultures of STEC showed a threshold<br />
of the VIDAS ESPT around 10 2 -10 3 CFU/mL. The same study ma<strong>de</strong> with dilutions of specific<br />
STEC strains mixed with non-specific bacteria, showed a sensitivity threshold of the test<br />
between 10 2 and 10 4 CFU/mL according to serogroups (Table 3).<br />
Table 3: Threshold concentration for VIDAS ESPT on broths of STEC and non-STEC strains.<br />
Serogroup O26 O103 O111 O145 O157<br />
ESPT sensitivity (CFU/mL) pure<br />
broth suspension of STEC<br />
ESPT sensitivity (CFU/mL) broth<br />
suspension of STEC with another<br />
non-STEC bacteria<br />
10 3 10 2 10 2 10 3 10 2<br />
10 4 10 2 10 2 10 4 10 2<br />
The threshold was <strong>de</strong>termined as soon as specific strains were isolated on plates<br />
- Sensitivity study on artificially inoculated samples<br />
The assay performed post-enrichment, on artificially inoculated samples showed a sensitivity<br />
threshold of the VIDAS ESPT for E. coli O26, O103, O111, O145 and O157 research around<br />
10 3 -10 4 CFU/mL according to the serogroups. With the IMS method the results showed a<br />
sensitivity threshold of 10 3 -10 5 CFU/mL according to the serogroups (Table 4).<br />
Table 4: Performance of two immuno-concentration methods: VIDAS ESPT and IMS, for the<br />
isolation of “gang of five” in post enriched raw ground beef samples artificially inoculated.<br />
138