Association of toxic shock toxin-1 determinant with a heterologous insertion at multiple loci in the Staphylococcus aureus chromosome.

Most Staphylococcus aureus strains associated with toxic shock syndrome and producing toxic shock syndrome toxin 1 (TSST-1) require tryptophan because of a genetic defect in tryptophan biosynthesis. The association between TSST-1 production and tryptophan auxotrophy was not correlated with the phage type, the colonization site, or the disease status of the patient from whom the isolate came. Protoplast fusion and transformation mapping located the genetic determinant of TSST-1 production (tst) very close to the trp operon in such strains and very close to tyrB in a Trp+ TSST-1+ strain. Southern blot hybridization of ClaI-restricted chromosomal DNA with a tst-specific probe revealed a common homologous segment in all of the Trp+ strains with tst linked to tyrB. These results confirmed that the tst determinant in Trp- strains is located at one site, whereas in Trp+ TSST-1+ strains the determinant is located elsewhere on the S. aureus chromosome. It is suggested that the TSST-1 determinant is associated with the insertion of a transposonlike segment into several sites on the S. aureus chromosome.