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

Abstract

Objectives: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. Methods: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. Results: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. Conclusion: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.

Development of antibodies against recombinant staphylococcal enterotoxin B from food poisoning cases

“…Based on the principles of antibody interactions, ELISA allows for easy visualization of results and can be completed without the use of additional radioactive materials. ELISA has become an increasingly important technique in detecting food poisoning agents [11,19].…”

Magnetic Nanoparticle-Based Fluorescence Immunoassay for Determination of Ochratoxin A in Milk

“…Briefly, the used solid carriers were APTES-modified MNPs. They were produced and modified in our laboratory by Syrris Globe system, UK (Godjevargova et al 2019). Whole antibody or F(ab′) 2 fragment was covalently immobilized onto APTES-modified MNPs by glutaraldehyde.…”

“…Another advantage of magnetic separation is removal of sample components that could affect subsequent fluorescence detection. There are many publications on IFA developed using MNPs (Godjevargova et al 2019;Ivanov et al 2019;Qin et al 2019). Usually the MNPs are used for extraction of OTA, and its detection is performed with different analytical tools (Sargazi and Majd 2017).…”