Use of the polymerase chain reaction for specific detection of type A, D and E enterotoxigenic Staphylococcus aureus in foods.

By comparison with the DNA sequences coding for Staphylococcus aureus enterotoxins (ents) A, B, C, D and E, oligonucleotides unique to the entA, entD and entE genes were synthesized and used as polymerase-chain-reaction (PCR) primers for the specific detection of type A, D or E enterotoxigenic S. aureus. The relative molecular weights of the PCR products amplified with these primers were 210, 333 and 456 bp, respectively. Despite the high relatedness among these S. aureus enterotoxin genes, each primer pair allows specific detection with total discrimination from other types of enterotoxigenic S. aureus. DNA from non-enterotoxigenic S. aureus or from non-S. aureus would not interfere with the PCR results either. Primers designed for entE detection allow the discrimination of entE strains that when assayed by a serological method might be classified as entA-producing strains. Study of the detection sensitivity showed that by using these primers, DNA from 10(0) cells of enterotoxigenic S. aureus could be detected unambiguously. When these oligonucleotide primers were used for the detection of S. aureus in foods, 10(0)-10(1) cells per gram of food could be detected and the naturally contaminating microflora in the food sample did not interfere with the detection.