Twenty-five and three strains of Escherichia coli O157:H7 were identified from 25 tenderloin beef and three chicken
meat burger samples, respectively. The bacteria were recovered using the immunomagnetic separation procedure followed
by selective plating on sorbitol MacConkey agar and were identified as E. coli serotype O157:H7 with three primer pairs
that amplified fragments of the SLT-I, SLT-II and H7 genes in PCR assays. Susceptibility testing to 14 antibiotics showed
that all were resistant to two or more antibiotics tested. Although all 28 strains contained plasmid, there was very little
variation in the plasmid sizes observed. The most common plasmid of 60 MDa was detected in all strains. We used DNA
fingerprinting by randomly amplified polymorphic DNA ŽRAPD. and pulsed-field gel electrophoresis ŽPFGE. to compare
the 28 E. coli O157:H7 strains. At a similarity level of 90%, the results of PFGE after restriction with XbaI separated the E.
coli O157:H7 strains into 28 single isolates, whereas RAPD using a single 10-mer oligonucleotides separated the E. coli
O157:H7 strains into two clusters and 22 single isolates. These typing methods should aid in the epidemiological
clarification of the E. coli O157:H7 in the study area