Characterization of the most prevalent colonization factor antigens present in Chilean clinical enterotoxigenic Escherichia coli strains using a new multiplex polymerase chain reaction.

Current methods to detect the colonization factor antigens (CFAs) associated with enterotoxigenic Escherichia coli (ETEC) strains are cumbersome, with some methods requiring antibodies that are not readily available. To achieve a gene-based method, we designed 2 multiplex polymerase chain reaction reactions to detect genes encoding the most common ETEC fimbrial colonization factors, including CFA/I and coli surface (CS) antigens CS1, CS2, CS3, CS4, CS5, and CS6. Analysis of 183 clinical ETEC strains shows that the most prevalent colonization factors were CFA/I only, CS1 and CS3, CS2 and CS3, and CS6 only. Interestingly, we identified 3 clinical isolates expressing CS1 only without its regulator rns. The method described here proved to be rapid and robust and correlates well with phenotypic expression of the CFAs, becoming a novel molecular diagnostic and research tool for future epidemiologic studies.