Purpose: In this study, cascade signal amplification in ELISA involving ds-ELISA and ic-ELISA was established to sensitively detect Escherichia coli O157:H7.
Methods: A complex was formed comprising anti-E. coli O157:H7 pAb, E. coli O157:H7, biotinylated anti-E. coli O157:H7 mAb, streptavidin, and biotinylated β-lactamase in ds-ELISA. Penicillin solution was then added into the ELISA well and hydrolyzed by β-lactamase. Afterward, the penicillin solution was transferred to ic-ELISA and sensitively detected.
Results: In the cascade signal amplification system, increasing the amount of added E. coli O157:H7 resulted in more β-lactamase and less penicillin. The detection sensitivity of E. coli O157:H7, which was 20 CFU/ml with the cascade signal amplification in ELISA, was 1,000 higher than that of traditional ELISA. Furthermore, the novel method can be used to detect E. coli O157:H7 in milk.
Significance: This new signaling strategy will facilitate analyses of highly sensitive foodborne pathogens.