Molecular Typing and Variations in Amount of Gene Expression of TSST-1-Producing Clinical Isolates.

The toxic shock syndrome toxin-1 (TSST-1), encoded by gene, has been proposed to cause staphylococcal toxic shock syndrome (TSS) in a susceptible host, which highlights the need to evaluate the level of gene expression and molecular genetic characteristics of the -positive isolates. A total of 916 isolates collected from seven hospitals in China were screened for the gene. The positive isolates were characterized by , SCC, PFGE, and typing. Representative strains were also subjected to MLST typing. qRT-PCR was used to quantify and major virulence regulator genes expression. We also sequenced the regions of promoter and open reading frame (ORF) of to investigate whether they correlate with the variation in expression. We found 208 (22.7%) of surveyed isolates including 198 (29.8%) of MRSA and 10 (4.0%) of MSSA isolates harbored the gene. The most common clone among positive MRSA isolates belonged to ST5 (CC5)-2-t002-SCCII. The amount of mRNA varied 8.4-folds among clinical isolates. Sequencing the promoter revealed a base T deletion in high expressed isolates. As for major virulence regulators, , and in four differentially expressed strains were detected to be highly expressed, respectively. Our study revealed high prevalence of ST5 (CC5)-2-t002-SCCII clone among positive MRSA in hospitals from China. The levels of expression among clinical isolates varied, which may be associated with promoter and variations in specific virulence regulators.