Xihong Zhao, Xiaowei He*, Wenmei Li, Yao Liu, Liansheng Yang and Jihua Wang
Escherichia coli O157:H7 is a serious and common human pathogen that can cause diarrhoea, haemorrhagic colitis, and haemolytic uraemic syndrome (HUS). In this study, the synthesis and identification of colloidal gold particles and antibody-colloidal gold conjugates probe specific to E. coli O157:H7 were performed, and the preparation of colloidal gold immunochromatographic strip based the biotin-streptavidin system was developed for detection of E. coli O157:H7.Monodispersional nanogold colloid was synthesized and preparation of nanogold-labeled polyclonal antibody probe to E. coli O157:H7 by citrate method. Combination of antibody with nanogold particles was also characterized by UV-visible (UV-vis) light absorption spectra and transmission electron microscopy (TEM). Furthermore, nanogold-labeled probe was used to develop an immunochromatographic (IC) strip for E. coli O157:H7 analysis. With this method, analysis could be completed in less than 10 min. Examination of the 65 known strains (36 E. coli O157 strains and 29 serotypes other than E. coli) showed 98.5% specifity and 100% sensitivity, only yield a false-positive reaction with Salmonella choleraesuis . The sensitivity of the IC strip was tested using 10-fold dilution E. coli O157 in foods, could be detected at a minimum of 2.3 × 103 CFU/ml without enrichment and 2.3 CFU/ml after enrichment. Application of IC strip test were performed on 265 water samples, 340 beef samples, 208 milk samples and 120 cake samples after enrichment, the specificity of the strip was 99.2, 97.9, 94.6 and 94.9%, respectively. The sensitivity of the strip was 100% agreement with tradition culture method. The established method is very useful for monitoring E. coli O157 containment in food samples.
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