The Open Biotechnology Journal

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Immunofluorescence Assay Using Monoclonal and Polyclonal Antibodies for Detection of Staphylococcal Enterotoxins A in Milk

Tzonka Godjevargova1, *, Zlatina Becheva1, Yavor Ivanov1, Andrey Tchorbanov2
1 Department of Biotechnology, “Prof. Dr Asen Zlatarov” University, Burgas, Bulgaria
2 Bulgarian Academy of Sciences, Institute of Microbiology, Sofia, Bulgaria



Staphylococcus aureus is a Gram-positive microorganism. S. aureus can grow in various foods and cause food poisoning by secreting enterotoxins. The most common enterotoxins involved in food poisoning are staphylococcal enterotoxin A and staphylococcal enterotoxin B, but Staphylococcal Enterotoxin A (SEA) is predominant. The main types of food contaminated with SEs are meat and meat products, poultry and eggs, milk and dairy products. The aim of this study was to develop a rapid and sensitive fluorescence immunoassay for detection of staphylococcal enterotoxin A in milk.


Monoclonal and polyclonal antibodies for SEA were produced and characterized. Competitive fluorescence immunoassay based on Magnetic Nanoparticles (MNPs) was performed and optimized. MNPs were used as a solid carrier of the antibodies. The first step of the assay was immunoreaction between the immobilized antibody onto MNPs and SEA in milk sample. Then the fluorescein-SEA conjugate was added to the sample. Thus, competitive immunoreaction between MNP-mAb/MNP-pAb with SEA and SEA-FITC was performed. These immuno-complexes were separated by a magnetic separator and the obtained supernatants were analyzed. The fluorescent signal from the excess of conjugated SEA was proportional to the SEA contained in the milk. The assay duration was only 30 min.


The fluorescence immunoassays performed with polyclonal antibody had linear ranges from 5 pg/mL to 100 ng/mL SEA in a buffer, and from 50 pg/mL to 50 ng/mL SEA in spiked milk samples. While the same assays performed with monoclonal antibody had linear ranges from 1 pg/mL to 20 ng/mL SEA in buffer, and from 10 pg/mL to 10 ng/mL SEA in spiked milk samples. The detection limits of the developed immunoassays performed in milk were: 48 pg/mL with polyclonal antibody and 9 pg/mL with monoclonal antibody.


A rapid and sensitive fluorescence immunoassay based on magnetic nanoparticles with a polyclonal and monoclonal antibody for determination of staphylococcal enterotoxin A in milk was developed.

Keywords: Staphylococcal enterotoxin A, Monoclonal antibody, Polyclonal antibody, Magnetic nanoparticles, Immunoassay, Milk.

Article Information

Identifiers and Pagination:

Year: 2019
Volume: 13
Issue: Suppl-1, M5
First Page: 137
Last Page: 145
Publisher Id: TOBIOTJ-13-137
DOI: 10.2174/187407070190130137

Article History:

Received Date: 15/04/2019
Revision Received Date: 22/07/2019
Acceptance Date: 22/09/2019
Electronic publication date: 15/11/2019
Collection year: 2019

© 2019 Godjevargova et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: ( This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Department of Biotechnology, “Prof. Dr Asen Zlatarov” University, Burgas, Bulgaria;
Tel: +35956716528, +359885604259; Email:

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