Detection of Escherichia coli O157:H7 using gold nanoparticle labeling and inductively coupled plasma mass spectrometry.

O157:H7 is a serotype of enterohemorrhagic Escherichia coli (EHEC) and one of the major causes of food-borne illness. Protection of food safety against bacterial contamination and rapid diagnosis of infection require simple and fast assays for detection of bacterial pathogens, including E. coli O157:H7. We describe here a rapid and sensitive assay for the E. coli O157:H7 bacteria by using antibody affinity binding, gold nanoparticle (Au NP) labeling, and inductively coupled plasma mass spectrometry (ICPMS) detection. Taking advantage of the signal amplification property of Au NPs and the high sensitivity of ICPMS, the assay was able to detect as few as 500 E. coli O157:H7 cells in 1 mL of sample (500 CFU/mL). Tests with nonpathogenic E. coli (DH5alpha, AlphaTauCC35218, and ATCC25922) showed high specificity of the assay for E. coli O157:H7. Each assay was completed within 40 min. Demonstration of this assay for E. coli O157:H7 suggests its potential for detecting a variety of bacterial pathogens.