A novel multiplex and glycoprotein-based immunochromatographic serologic IgM test for the rapid diagnosis of <i>Escherichia coli</i> O157 and O145 causing bloody diarrhea and hemolytic uremic syndrome

Shiga toxin-producing <i>Escherichia coli</i> (STEC) are the main etiological agents of hemolytic uremic syndrome (HUS). Good clinical management of STEC infections and HUS depends on early, rapid, and accurate diagnosis. Here, we have developed and evaluated the first multiplex and glycoprotein-based immunochromatographic test for the detection of IgM antibodies against the O-polysaccharide of the lipopolysaccharide of <i>E. coli</i> O157 and O145 in human serum samples. A retrospective study was carried out resulting in a diagnostic sensitivity of the <i>E. coli</i> O157/O145 LFIA (lateral flow immunoassay) of 97.1% and 98.9% for O157 and O145, respectively, and 97.9% for both serogroups. The diagnostic specificity was 98.7% for O157 and O145, and the overall specificity 97.4%. In samples obtained before 3 days after the onset of diarrhea, the detection percentage was 83%, increasing to 100% from 3 days onward. Finally, the association of bloody diarrhea (BD) or HUS cases to an STEC infection increased from 22.8% to 77.2% when stool culture and <i>stx</i>/Stx detection were combined with serology by LFIA. Our results demonstrate that the <i>E. coli</i> O157/O145 LFIA is a highly accurate and serospecific test for the early and rapid diagnosis of <i>E. coli</i> O157 and O145 infections in BD or HUS cases. This test allows the detection of specific IgM antibodies very early in the course of the infection, making it an ideal diagnostic tool to be implemented in pediatric emergencies and, thus, avoid delays in the application of the correct supportive or specific treatment and prevent complications associated with HUS.