[Identification of Escherichia coli O157 antigen by polymerase chain reaction]

An assay was developed for the specific detection of Escherichia coli O157 using PCR, because O serological cross-reactivities have been reported between E. coli O157 and some E. coli, other bacterial species. PCR amplification of E. coli O157 rfbE (Ec O157:H7) gene that is necessary for the expression of the O157 antigen, was performed for the identification of E. coli O157. All Shiga toxin-producing Escherichia coli (STEC) O157:H7 and O157:H, non-STEC O157 strains were positive, and other non-O157 E. coli strains were negative by PCR. All tested strains of other bacterial species, like Salmonella O30 and Citrobacter freundii which gave positive results with O157 detection kits, were negative by PCR. It is recommended that PCR amplification of O157 rfbE gene is one of the most specific method for E. coli O157 identification.