[Evaluation of molecular and immunoenzymatic assays for detecting Enterohemorrhagic E coli in food borne outbreaks].
BACKGROUND
Enterohemorrhagic Escherichia coli (EHEC), is an emergent pathogen that causes sporadic infections and outbreaks of gastroenteritis associated with consumption of contaminated food products. Because detection of EHEC in diarrhea patients is not routinely performed, infection is most probably underestimated.


OBJECTIVE
To compare three techniques to detect EHEC: Colony hybridization with DNA probes, polymerase chain reaction (PCR) for the detection of stx1 and stx2 genes and immunoenzymatic detection by ELISA (Premier EHEC) of Stx1 and Stx2 toxins.


METHODS
Four outbreaks of food-borne gastroenteritis were studied including 16 patients and 78 strains of E coli. Twenty-one (26.9%) strains, hybridized with the stx1 probe, 1 (1.3%) hybridized only with the stx2 probe and 36 (46.1%) with both probes. PCR amplification for cytotoxin genes was observed in 6 strains (7.7%) from the second outbreak studied. The immunoenzymatic assay detected the cytotoxins in 18 (23.0%), of the 78 studied strains. Agreement between probes and ELISA was 44.8%, between PCR and probes 34.7% and 82.4% between ELISA and PCR.


CONCLUSIONS
These results indicate a variable yield among different EHEC detection techniques. Considering PCR as the gold standard, ELISA technique showed a better sensitivity and specificity than probes.
Programa de Microbiología, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina de la Universidad de Chile, Servicio de Salud Metropolitano del Ambiente (SESMA), Santiago de Chile.
Maricel
M
Vidal
Mónica
M
Carreño
Roberto
R
Vidal
Carolina
C
Arellano
Verónica
V
Solari
Valeria
V
Prado
D001483:Base Sequence; D002677:Chile / Q000453:epidemiology; D003603:Cytotoxins / Q000235:genetics / Q000302:isolation & purification; D004196:Disease Outbreaks; D004797:Enzyme-Linked Immunosorbent Assay; D004927:Escherichia coli Infections / Q000175:diagnosis* / Q000453:epidemiology / Q000382:microbiology; D019453:Escherichia coli O157 / Q000302:isolation & purification*; D005517:Foodborne Diseases / Q000175:diagnosis / Q000453:epidemiology / Q000382:microbiology; D005759:Gastroenteritis / Q000175:diagnosis / Q000453:epidemiology / Q000382:microbiology; D005821:Genetic Techniques; D006801:Humans; D007124:Immunoenzyme Techniques / Q000379:methods*; D009693:Nucleic Acid Hybridization; D009841:Oligonucleotides; D016133:Polymerase Chain Reaction; D012680:Sensitivity and Specificity
D003603:Cytotoxins; D009841:Oligonucleotides