Development of PCR assays targeting the genes involved in synthesis and assembly of the new Escherichia coli O174 and O177 O antigens

Escherichia coli O174 and O177 are newly described O serogroups which were reported as human pathogens. Identification of these strains by serotyping has been restricted, as the required sera are not commercially available. In this study, a collection of 13 E. coli O174 strains and 12 E. coli O177 strains was studied on the O:H serotypes and virulence markers. The O-antigen gene clusters of E. coli O174 and O177 were sequenced, and associated genes were assigned functions on the basis of homology. Two genes, each specific for E. coli O174 and O177, were identified. PCR assays based on the O-antigen-specific genes were developed and tested on 25 clinical and environmental isolates of those two serogroups as well as 26 isolates of other O serogroups. As little as 1 pg per μl of chromosomal DNA and as few as 0.1 CFU per g of pork and water samples were detected for either strain. The PCR assays established in this study were shown to be highly sensitive and reliable and could be the method of choice for detection of these two human pathogens from clinical, food, and other environmental samples.