Comparison between a PCR-ELISA test and the vero cell assay for detecting Shiga toxin-producing Escherichia coli in dairy products and characterization of virulence traits of the isolated strains.
OBJECTIVE
This paper provides information on a PCR-ELISA method for detecting Shiga toxin-producing Escherichia coli (STEC), and on their prevalence in dairy products.


RESULTS
The sensitivity and specificity of the test was evaluated using pure cultures, spiked and naturally-contaminated samples. A comparative study with vero cytotoxicity testing was conducted, and STEC isolated from naturally-contaminated samples were characterized. The PCR-ELISA test was highly specific and sensitive, and detected 14% more positive samples than the vero cell assay. The prevalence of STEC in raw milk and unpasteurized cheese was 21.5% and 30.5%, respectively, while samples from the 'dairy environment' and from pasteurized cheese were less contaminated. The 34 strains of STEC isolated from natural samples showed that some of them carried virulence genes.


CONCLUSIONS
No conclusion can be drawn at the moment concerning the potential risk to consumers.


CONCLUSIONS
These data show the necessity of valuable screening methods to appreciate the virulence of STEC.
Fach
P
P
Agence Française de Sécurité Sanitaire des Aliments, Laboratoire d'Etudes et de Recherches sur l'Hygiène et la Qualité des Aliments, Unité: Atelier de Biotechnologie, Maisons-Alfort, France. p.fach@afssa.fr
Perelle
S
S
Dilasser
F
F
Grout
J
J
D000818:Animals; D001681:Biological Assay; D002522:Chlorocebus aethiops; D003611:Dairy Products / Q000382:microbiology*; D004797:Enzyme-Linked Immunosorbent Assay; D004926:Escherichia coli / Q000235:genetics / Q000302:isolation & purification* / Q000472:pathogenicity; D005516:Food Microbiology; D005798:Genes, Bacterial; D016133:Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D022603:Shiga Toxins / Q000032:analysis* / Q000235:genetics; D014709:Vero Cells; D014774:Virulence
D022603:Shiga Toxins