Abstract
Staphylococcal enterotoxins (SEs) are the cause of staphylococcal food poisoning (SFP) outbreaks. Recently, many new types of SEs and SE-like toxins have been reported, but it has not been proved whether these new toxins cause food poisoning. To develop an immunoassay for detection of SE-like J (SElJ), a non-characterized toxin in SFP, a mutant SElJ with C-terminus deletion (SElJ∆C) was expressed and purified in an E. coli expression system. Anti-SElJ antibody was produced in rabbits immunized with the SElJ∆C. Western blotting and sandwich enzyme-linked immunosorbent assay (ELISA) detection systems were established and showed that the antibody specifically recognizes SElJ without cross reaction to other SEs tested. The limit of detection for the sandwich ELISA was 0.078 ng/mL, showing high sensitivity. SElJ production in S. aureus was detected by using the sandwich ELISA and showed that selj-horboring isolates produced a large amount of SElJ in the culture supernatants, especially in that of the strain isolated from a food poisoning outbreak in Japan. These results demonstrate that the immunoassay for detection of SElJ is specific and sensitive and is useful for determining the native SElJ production in S. aureus isolated from food poisoning cases.
Highlights
Staphylococcal enterotoxins (SEs), which are produced by Staphylococcus aureus, exhibit emetic activity in primates and are the causative agents of food poisoning cases in humans [1]
Selj was found as a gene located with several other SE genes, selj with sed and ser, or selj with ser, ses, and set, in the same pathogenic plasmids in S. aureus isolated from food poisoning cases [3,11]
SE-like J (SElJ) and its potential risk for food poisoning, we firstly prepared a recombinant SElJ and analyzed its biological properties and developed an immunoassay, sandwich enzyme-linked immunosorbent assay (ELISA), for detection of SElJ and determined the SElJ production of S. aureus isolates from food poisoning outbreaks
Summary
Staphylococcal enterotoxins (SEs), which are produced by Staphylococcus aureus, exhibit emetic activity in primates and are the causative agents of food poisoning cases in humans [1]. These toxins are superantigens, which have the ability to stimulate a large population of T cells bearing specific. Genes, indicating that the recently described SEs and SEls could be the causative agents of food poisoning and play important roles in the virulence of S. aureus [8,9,10]. The toxin proteins of SED, SER, SES, and SET have been characterized in their emetic and superantigenic activities and reported to be involved in staphylococcal food poisoning [1,4]. Selj-harboring S. aureus produced a large amount of SElJ, indicating that SElJ could be an important risk factor involving in food poisoning outbreak
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