Molecular Characterization of Escherichia coli O157:H7 Isolates Obtained From Bovine and Porcine Carcasses

Abstract

ISEE-808 Objective: The objectives of this study were to determine the presence and/or absence of Escherichia coli serotype O157:H7 in bovine and porcine carcasses, and molecular characterization of the isolated E. coli by means of PCR. Materials and Methods: The study was carried out between February and October 2004. Two slaughterhouses were sampled, 1 of porcine (I) and 1 of bovine (II) from La Comarca Lagunera, Mexico. Samplings were made in 2 dates for each slaughterhouse, February 20, 2004, and March 15, 2004, for site I and March 02, 2004, and March 24, 2004, for site II. The isolates of E. coli were obtained using the NOM-030 z00, 1995, but we also used the NOM-109-SSAI, 1994. For the analysis in life surfaces 15 carcasses were sampled randomly on each slaughterhouse, using a sterile sponge (NASCO) in 3 different places. The characteristic colonies were confirmed with biochemical tests using API 20 E (Biomereux, France) and the serotype using the serology kit (DIFCO). From the samples in which presence of E. coli O157:H7 was confirmed, DNA was isolated for the molecular characterization by PCR. Results: Of the 18 isolates, 12 were positive by PCR to rfbE and fliC genes, which determined O157:H7 serotype. Of those 12, 1 bovine, and 3 porcine carcasses samples were positive by PCR to stx1, stx2, and eaeA genes; therefore, they were considered enterohemorrhagic strains. The differences found in the positive carcasses number to any of the genes were not statistically significant. Conclusions: E. coli O157:H7 was found in both carcasses types, representing a risk for the human health; so strict hygienic and handling practices should be taken to avoid consumption of contaminated meat by final consumers.