[Escherichia coli O157:H7 detection in fresh ground beef and hamburgers].

Escherichia coli O157:H7 is an emergent pathogen associated with food transmitted diseases. In 1982, Escherichia coli O157:H7 was for the first time identified as the cause of two hemorrhagic colitis outbreaks in the United States. It is now well known that most cases of hemolytic uremic syndrome are caused by these bacteria. The objective of this work was to detect the microorganism in fresh ground beef and hamburgers. From April 2003 to August 2004 samples were taken at sale points of our supermarket chain, totalling 37 and 43, respectively. These samples were processed using the EC selective enrichment broth containing novobiocin, then followed by the application of an immunocapture method (TECRA E. COLI O157 IMMUNOCAPTURE ECOICM 20), and later isolation in MacConkey sorbitol agar with cefixime and potassium tellurite, in a chromogenic medium. The suspected strains were genotypically characterized by PCR detection of the stx1, stx2, eaeA, and EHEC-hlyA genes, and by a colony blot hybridization assay. Serotyping, antimicrobial susceptibility patterns, and production of Stx by a specific cytotoxicity assay on Vero cells were also determined. E coli O157:H7 was isolated in only one fresh ground beef sample (2,7%), identified as gene eae (+)/ stx2/EHEC-hlyA.