Rapid isolation and detection of Escherichia coli O157:H7 by use of rainbow agar O157 and PCR assay.

ABSTRACT

This study has evaluated the use of a commercially available Rainbow agar O157 and polymerase chain reaction (PCR) assays for the detection of Shiga-like toxin producing Escherichia coli and to serotype E. coli O157H7 from raw meat. The Rainbow agar O157 was found to be selective and sensitive for the screening of the E. coli O157 from artificially and naturally contaminated meat samples. Shiga-like toxin producing E. coli were identified with two primer pairs that amplified fragments of the SLT-I (384 bp) and SLT-II (584 bp). E. coli O157H7 was serotyped with a primer pair specified for the H7 flagellar gene, which amplify specific DNA fragments (625 bp) from all E. coli O157H7 strains. The use of Rainbow agar O157 described allows for the presumptive isolation of E. coli O157 in 24 hours. Identification and confirmation of the presumptive isolates as E. coli O157H7 by PCR assays require additional 6-8 hours. The above-mentioned screening and identification procedures should prove to be a very useful method since it allows for the specific detection of E. coli O157H7.