Joint-detection of Salmonella typhimurium and Escherichia coli O157:H7 by an immersible amplification dip-stick immunoassay.

ABSTRACT

To explore the superiority of multifunctional nanocomposites and realize the joint-detection of foodborne pathogens, an immersible amplification dip-stick immunoassay (DSIA) was exploited for the sensitive detection of Salmonella typhimurium (S. typhi) and Escherichia coli O157H7 (E. coli O157H7). Saving for the basic colorimetric performance, the reporter molecule of CoFe2O4 (CFO) possesses multivalent elements (Co2+/3+, Fe2+/3+) as well as multifunction of superior catalase-like activity and magnetic properties. By dint of the catalytic activity of CFO, a directly immersible amplification can be simply achieved to endure the DSIA with an intensive signal and a dual-visible mode for the determination of S. typhi and E. coli O157H7. In virtue of the magnetic separation and enrichment capability of the CFO, the DSIA can perform a matrix-interference-free detection and obtain a dynamic detection range of 102-108 CFU/mL and a low assay limit of 102 CFU/mL. Moreover, the DSIA has reasonable recovery rates for contamination monitoring of two target bacteria in milk and beef samples. Our research provides a persuasive supplement for the application of multifunctional nanocomposites in the ongoing dip-stick immunoassay and an alternative strategy for the efficient detection of foodborne pathogens.