Genes specific for Escherichia coli O157:H7 and E. coli O26 serotypes as molecular probes for rapid identification

In this study, the O-antigen was cloned from E. coli O26 and E. coli O157 into the cosmid vector, pCosEMBL2. Screening of the cosmid library was done by Western analysis using polyclonal antisera specific to O26 and O157. SDS-PAGE was used to localize the LPS core and the O-antigen subunits from recombinant E. coli strains. Cosmid DNA from the O-Ag positive clones were used as DNA probes to study the distribution of the E. coli O157 and E. coli O26 rfb gene sequences. The DNA fragments that were identified from our cosmid clones appeared to be O-serotype specific for either E. coli O26 or E. coli O157. The information gained from the sequencing of these O-serotype specific DNA fragments will be used in the development of a PCR based method for detecting E. coli O26 and O157 serogroups.