Development of a lateral flow colloidal gold immunoassay strip for the simultaneous detection of Shigella boydii and Escherichia coli O157:H7 in bread, milk and jelly samples

A colloidal gold immunochromatographic strip (ICS) was proposed with double monoclonal antibodies (McAbs) for rapid detections of multiple foodborne pathogens, and we successfully developed a model strip for simultaneous detection of Shigella boydii (S. boydii) and Escherichia coli O157:H7 (E. coli O157:H7) in this study. The sensitivity of the strip test was determined to be 106 CFU/mL for both S. boydii and E. coli O157:H7. There was no cross-reaction with other related bacteria. Parallel analysis of pathogen detection from bread, milk and jelly showed consistent results between the strip test and enzyme-linked immunosorbent assay (ELISA). The detection limit was substantially improved to 4 CFU/mL of the original bacterial content after pre-incubation of the bread, milk and jelly samples in broth for 10, 10 and 8 h respectively. This ICS was able to finish test within 5-10 min and has advantages in high throughput and easy operation without requiring sophisticated equipment and specialized skills. Overall, to our knowledge, this is the first report of semi-quantitative ICS for simultaneously detecting two pathogens. This protocol might provide insight into the development of ICS technology for simultaneously examining multiple food-borne pathogens from foods.