The Detection of Enterotoxins and Toxic Shock Syndrome Toxin Genes in Staphylococcus aureus by Polymerase Chain Reaction

Abstract

A simple polymerase chain reaction (PCR)-based procedure was developed for the detection of fragments of staphylococcal enterotoxins (SEs) SEA, SEB, SEC, SED, SEE, SEG, SEH, and SEI together with the toxic shock syndrome toxin (TSST-1) genes of Staphylococcus aureus. One hundred and twenty-nine cultures of S. aureus were selected, 39 of which were recovered from 38 suspected staphylococcal food-poisoning incidents. The method was reproducible, and 32 different toxin genotypes were recognized. The presence of SE genes was associated with S. aureus strains reacting with phages in group III, and the TSST-1 gene with phages in group I. There was a 96% agreement between the PCR results for detection of SEA–D and TSST-1 as compared with a commercial reverse passive latex agglutination assay for the detection of SEs from cultures grown in vitro. Enterotoxin gene fragments were detected in S. aureus cultures recovered from 32 of the 38 suspected staphylococcal food poisoning incidents, and of these, 17 were associated with SEE, SEG, SEH, and SEI in the absence of SEA–D. Simple PCR procedures were also developed for the detection of SE directly in spiked food samples, and this was most successfully achieved in mushroom soup and ham. Detection was less successful in three types of cheese and in cream. SEA or SEB were detected by enzyme-linked immunosorbent assay in three food samples (two of which were associated with food poisoning incidents) naturally heavily contaminated with S. aureus: the appropriate SEA or SEB gene fragments were detected directly in these three foods by PCR.