Identification of enteroinvasive Escherichia coli and Shigella strains in pediatric patients by an IpaC-specific enzyme-linked immunosorbent assay.

A new method, a monoclonal antibody-based enzyme-linked immunosorbent assay (ELISA) recognizing a secreted, invasion plasmid-coded protein antigen (IpaC), was used to identify enteroinvasive Escherichia coli and Shigella strains among colonies from 859 cultures of fecal samples from children in Kuwait. A total of 33.8% of the samples were diarrheal. By the immunoassay, enteroinvasive E. coli strains were identified from two diarrheal samples but from none of the samples from children without diarrhea. These strains were fully virulent and belonged to serogroup O28ac. In addition, 26 Shigella strains were also recognized by the ELISA, while only 23 were isolated by routine biotyping and serotyping. For two diarrheal patients, Shigella was identified by culture only. The study showed that the IpaC-specific immunoassay is a simple and useful tool for identifying enteroinvasive strains. Furthermore, by reporting the first enteroinvasive E. coli isolates from Kuwait, the study indicates the presence of this group of pathogens as a potential source of diarrhea in the region.