A rapid and highly sensitive protocol for the detection of Escherichia coli O157:H7 based on immunochromatography assay combined with the enrichment technique of immunomagnetic nanoparticles

Hui Qi¹, Zhen Zhong¹, Han-Xin Zhou¹, Chun-Yan Deng¹, Hai Zhu², Jin-Feng Li², Xi-Li Wang², Fu-Rong Li^1,3
1Clinical Medical Research Center, The Second Clinical Medical College (Shenzhen People's Hospital), Jinan University, ²Shenzhen Bioeasy Biotechnologies Co, Ltd, ³Shenzhen Institute of Gerontology, Shenzhen, People's Republic of China

Background: Escherichia coli O157:H7 (E. coli O157:H7) is an important pathogenic bacterium that threatens human health. A rapid, simple, highly sensitive, and specific method for the detection of E. coli O157:H7 is necessary.
Methods: In the present study, immunomagnetic nanoparticles (IMPs) were prepared with nanopure iron as the core, coated with E. coli O157:H7 polyclonal antibodies. These IMPs were used in combination with immunochromatographic assay (ICA) and used to establish highly sensitive and rapid kits (IMPs+ICA) to detect E. coli O157:H7. The kits were then used to detect E. coli O157:H7 in 150 food samples and were compared with conventional ICA to evaluate their efficacy.
Results: The average diameter of IMPs was 56 nm and the amount of adsorbed antibodies was 106.0 µg/mg. The sensitivity of ICA and IMPs+ICA was 10⁵ colony-forming units/mL and 10³ CFUs/mL, respectively, for purified E. coli O157:H7 solution. The sensitivity of IMPs+ICA was increased by two orders, and its specificity was similar to ICA.
Conclusion: The kits have the potential to offer important social and economic benefits in the screening, monitoring, and control of food safety.

Keywords: colloidal gold, immunomagnetic nanoparticles, Escherichia coli O157:H7, immunochromatographic assay