Sandwich-Based Immunosensor for Dual-Mode Detection of Pathogenic F17-Positive Escherichia coli Strains

Bacterial diseases cause tremendous economic losses due to high morbidity and mortality in livestock animals. F17A protein, the major subunit of F17 fimbriae, is one of the most prevalent and crucial virulence factors among the pathogenic Escherichia coli (E. coli) isolated from diarrheic and septicemic animals of various species. Purification and detection of this protein is regarded as an interesting field of investigation due to its important role as a therapeutic target, such as vaccines, and as a diagnostic tool. In this context, polyclonal rabbit antibodies recognizing F17A protein (anti-F17A antibody) were developed and used for its detection. In fact, sandwich biosensor using anti-F17A/gold nanoparticles conjugates as capture probe and anti-F17A antibody labelled with horseradish peroxidase as signal amplification probe was developed for electrochemical and fluorescent detection of purified F17A protein and live F17-positive E. coli bacteria. Good specificity and sensitivity for detection of F17-positive E. coli strains were obtained. The dynamic range for the biosensor varies from 1 x 10(2) to 1 x 10(9) CFU center dot mL(-1) (R-2 = 0.998) and the detection limit (LOD) and the IC50 value were estimated to be 37 CFU center dot mL(-1) and 75 CFU center dot mL(-1), respectively.

Automated summary

Bacterial diseases in livestock animals cause significant economic losses. F17A protein, a crucial virulence factor in pathogenic Escherichia coli, has been identified as a promising therapeutic target and diagnostic tool. Researchers developed anti-F17A antibodies for the detection of this protein and successfully developed a biosensor for electrochemical and fluorescent detection of purified F17A protein and live F17-positive E. coli bacteria.