Evaluación de técnicas moleculares e inmunoenzimáticas para la detección de escherichia coli enterohemorrágico en brotes de toxi infecciones alimentarias / Evaluation of molecular and immunoenzymatic assays for detecting enterohemorrhagic escherichia coli in food borne outbreaks

RESUMO

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. Aim: 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. Material and methods: Four outbreaks of food-borne gastroenteritis were studied including 16 patients and 78 strains of E coli. Twenty one (26,9 percent) strains, hybridized with the stx1 probe, 1 (1,3 percent) hybridized only with the stx2 probe and 36 (46,1 percent) with both probes. PCR amplification for cytotoxin genes was observed in 6 strains (7,7 percent) from the second outbreak studied. The immunoenzimatic assay detected the cytotoxins in 18 (23,0 percent), of the 78 studied strains. Agreement between probes and ELISA was 44,8 percent, between PCR and probes 34,7 percent and 82,4 percent 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