Identification of Escherichia coli O172 O-antigen gene cluster and development of a serogroup-specific PCR assay

AIM: To characterize the locus for O-antigen biosynthesis from Escherichia coli O172 type strain and to develop a rapid, specific and sensitive PCR-based method for identification and detection of E. coli O172. METHODS AND RESULTS: DNA of O-antigen gene cluster of E. coli O172 was amplified by long-range PCR method using primers based on housekeeping genes galF and gnd Shot gun bank was constructed and high quality sequencing was performed. The putative genes for synthesis of UDP-FucNAc, O-unit flippase, O-antigen polymerase and glycosyltransferases were assigned by the homology search. The evolutionary relationship between O-antigen gene clusters of E. coli O172 and E. coli O26 is shown by sequence comparison. Genes specific to E. coli O172 strains were identified by PCR assays using primers based on genes for O-unit flippase, O-antigen polymerase and glycosyltransferases. The specificity of PCR assays was tested using all E. coli and Shigella O-antigen type strains, as well as 24 clinical E. coli isolates. The sensitivity of PCR assays was determined, and the detection limits were 1 pg microl(-1) chromosomal DNA, 0.2 CFU g(-1) pork and 0.2 CFU ml(-1) water. The total time required from beginning to end of the procedure was within 16 h. CONCLUSION: The O-antigen gene cluster of E. coli O172 was identified and PCR assays based on O-antigen specific genes showed high specificity and sensitivity. SIGNIFICANCE AND IMPACT OF THE STUDY: An O-antigen gene cluster was identified by sequencing. The specific genes were determined for E. coli O172. The sensitivity of O-antigen specific PCR assay was tested. Although Shiga toxin-producing O172 strains were not yet isolated from clinical specimens, they may emerge as pathogens.