Identification of Escherichia coli O114 O-antigen gene cluster and development of an O114 serogroup-specific PCR assay.

Screening for the Escherichia coli O serotype is the traditional test for identification of E. coli clones. The O-antigen gene cluster of the E. coli O114 type strain was sequenced, and 12 open reading frames were assigned functions on the basis of homology. By screening against all 186 E. coli and Shigella O serotypes, five genes specific to E. coli O114 were identified. A PCR assay based on the O-antigen-specific genes was developed and tested on 41 clinical isolates of E. coli O114. The PCR assay was shown to be highly specific and sensitive. When tested with pork and water samples, as few as 0.12 CFU of E. coli O114 g(-1) were detected. Thus, the PCR assays established in this study can be used to reliably identify E. coli O114 strains and may also be used to detect E. coli O114 strains in food, water, and other environmental samples.