A colony blot immunoassay to detect enteroinvasive Escherichia coli and Shigella in water samples

Aims: The aim of the study was to develop a colony blot immunoassay to detect Shigella and enteroinvasive Escherichia coli (EIEC) in water. Methods and Results: Spiked samples were filtered through nitrocellulose membranes. Colony prints on the filters were tested with a monoclonal antibody specific to IpaC, an antigen coded by the invasion plasmid of Shigella and EIEC. Invasive pathogens could be successfully detected with the technique, even in the presence of a large number of non-pathogenic bacterial cells. The method was significantly more sensitive in identifying pathogen-containing samples then the traditional culture-based approach. Conclusions: The IpaC-specific colony blot immunoassay is an inexpensive method for identifying the aetiological agents of bacillary dysentery in water samples. Significance and Impact of the Study: The technique could be particularly useful in detecting enteroinvasive E. coli which often remains undetected by bio- and serotyping.