Toxic Shock Syndrome Toxin I-Producing Staphylococcus aureus Isolates Contain the Staphylococcal Enterotoxin B Genetic Element but Do Not Express

Toxic shock syndrome toxin 1 (TSST-l) and staphylococcal enterotoxin B (SEB) are two examples of variable genetic traits produced by Staphylococcus aureus. Regarding phenotypes, most investigations have reported that SEB and TSST-1 are not coproduced in S. aureus. How-ever, it is unclear whether genotypically SEB (entB) and TSST-l (tst) genes are found within the same isolate. Gene probes specific for entB and tst showed that both genes were present within 8 TSST-1+ isolates analyzed. However, SEB was not produced by any of these isolates. In contrast, none of9 SEB-producing S. aureus isolates contained the TSST-1 genetic element DNA. Hybrid-ization of restriction fragments with TSST-1 and SEB genetic element probes and tryptophan auxotyping suggested that tst and entB are located in close proximity on the chromosome. The entB locus may be a preferred site of insertion for the TSST-1 genetic element, and such insertion may interfere with the expression of SEB. Staphylococcus aureus produces a wide variety of extracel-lular proteins, some of which have clearly been shown to be virulence factors in pathogenesis. Some of these exoproteins have variable traits in that they are produced by some S