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.