TOXIC SHOCK SYNDROME TOXIN 1-PRODUCING STAPHYLOCOCCUS-AUREUS ISOLATESCONTAIN THE STAPHYLOCOCCAL-ENTEROTOXIN-B GENETIC ELEMENT BUT DO NOT EXPRESS STAPHYLOCOCCAL-ENTEROTOXIN-B

Toxic shock syndrome toxin 1 (TSST-1) and staphylococcal enterotoxin B (SEB) are two examples of variable genetic traits produced by Staphyl ococcus aureus. Regarding phenotypes, most investigations have reporte d that SEB and TSST-1 are not coproduced in S. aureus. However, it is unclear whether genotypically SEB (entB) and TSST-1 (tst) genes are fo und within the same isolate. Gene probes specific for entB and tst sho wed that both genes were present within 8 TSST-1(+) isolates analyzed. However, SEB was not produced by any of these isolates. In contrast, none of 9 SEB-producing S. aureus isolates contained the TSST-1 geneti c element DNA. Hybridization of restriction fragments with TSST-1 and SEB genetic element probes and tryptophan auxotyping suggested that ts t 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 elem ent, and such insertion may interfere with the expression of SEB.