Comparison of 4 label-based immunochromatographic assays for the detection of Escherichia coli O157:H7 in milk

Publication date: July 2017
Source:Journal of Dairy Science, Volume 100, Issue 7
Author(s): Kai Luo, Liming Hu, Qi Guo, Chenghui Wu, Songsong Wu, Daofeng Liu, Yonghua Xiong, Weihua Lai
Immunochromatographic assays (ICA) are widely used to detect pathogens. In this study, we used traditional gold nanoparticles (GNP), quantum dots (QD), fluorescent nanoparticles (FNP), and europium (Eu) (III) chelate nanoparticles (EuNP) as ICA labels. We first compared the ability of the 4 ICA test strips to quantitatively detect Escherichia coli O157:H7 in milk. We then optimized various parameters influencing the ICA. The sensitivity to E. coli O157:H7 of the GNP-ICA, QD-ICA, FNP-ICA, and EuNP-ICA was 2.5 × 10⁴, 5 × 10³, 1.0 × 10³, and 5.0 × 10² cfu mL⁻¹, respectively. The EuNP-ICA exhibited the highest sensitivity. The amounts of monoclonal antibodies (mAb) per GNP-ICA, QD-ICA, FNP-ICA, and EuNP-ICA test strip were 0.16, 0.37, 0.04, and 0.10 μg, respectively. The corresponding coefficients of variation were 7.4 to 15.8%, 10.4 to 18.6%, 2.7 to 7.8%, and 6.9 to 10.5%, respectively. The FNP-ICA required the least mAb per test strip and had the best coefficient of variation. The linear ranges of GNP-ICA, QD-ICA, FNP-ICA, and EuNP-ICA were 1.0 × 10⁴ to 1.0 × 10⁶, 2.5 × 10³ to 1.0 × 10⁶, 2.5 × 10² to 2.5 × 10⁵, and 2.5 × 10² to 2.5 × 10⁵ cfu mL⁻¹, respectively. The FNP-ICA and EuNP-ICA had wider linear ranges than GNP-ICA and QD-ICA. Additionally, the FNP-ICA and EuNP-ICA showed better tolerance than GNP-ICA and QD-ICA in the milk samples. The FNP-ICA and EuNP-ICA showed remarkable potential for detection of pathogens in milk.



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