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. 2018 Sep;38(4):727-736.
doi: 10.5851/kosfa.2018.e11. Epub 2018 Sep 30.

Direct Detection of Escherichia coli, Staphylococcus aureus, and Salmonella spp. in Animal-derived Foods Using a Magnetic Bead-based Immunoassay

Jong-Hui Kim  1 , Jae Gyu Yoo  1 , Jun-Sang Ham  1 , Mi-Hwa Oh  1
Affiliations

Direct Detection of Escherichia coli, Staphylococcus aureus, and Salmonella spp. in Animal-derived Foods Using a Magnetic Bead-based Immunoassay

Jong-Hui Kim et al. Korean J Food Sci Anim Resour. 2018 Sep.

Abstract

In this study, an immuno-magnetic bead (IMB)-based assay was developed to simultaneously detect Escherichia coli, Staphylococcus aureus, and Salmonella spp. and was tested in four animal-derived foods: beef, ham, egg, and ricotta cheese. The IMB-based assay exhibited good specificity by binding to five E. coli serotypes [capture efficiency (CE) average (avg.) 90.4%], five S. aureus strains (CE avg. 91.4%), and five Salmonella serotypes (CE avg. 95.4%) but not binding to non-target bacteria (CE<10%). Furthermore, the assay detected all three pathogens with a detection limit of 10 CFU/g without the need for enrichment or additional platforms. Since the results demonstrated that the IMB-based assay can effectively separate and enrich target bacteria from a variety of animal-derived food matrixes, the assay exhibits good specificity for potential use in providing rapid, immunological, presumptive identification of pathogenic bacteria.

Keywords: Escherichia coli; Salmonella spp; Staphylococcus aureus; foodborne pathogen; immunomagnetic beads.

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Figures

Fig. 1
Fig. 1. Effect of immunomagnetic bead (IMB) concentration on capture efficiency (CE) against E. coli O157:H7 (5.6×104 CFU/mL).
CE was determined using the colony counting method, and error bars show SD (n=3). Superscripts with different letters within the same time are significantly different (p<0.05). 1) Statistical analysis of IMB concentration was performed by ANOVA with Duncan’s multiple range test at p<0.05. 2) NS, not significant.
Fig. 2
Fig. 2. Capture specificity (%) of antibody-conjugated immunomagnetic beads toward target bacteria from three mixed cultures.
(A) Five serotypes of E. coli and five non-target bacteria, (B) five strains of S. aureus and five non-target bacteria, and (C) five serotypes of Salmonella and five non-target bacteria. Capture efficiency (CE) was determined using the colony counting method. Error bars show SD (n=3).
Fig. 3
Fig. 3. Capture efficiency (%) of the mixture of E. coli serotypes, mixture of S. aureus strains, and mixture of Salmonella serotypes in artificially contaminated animal-derived foods.
See this image and copyright information in PMC

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