Complete nucleotide sequence of a Staphylococcus aureus exfoliative toxin B plasmid and identification of a novel ADP-ribosyltransferase, EDIN-C

The complete nucleotide sequence of pETB, a 38.2-kb Staphylococcus aureus p lasmid encoding the exfoliative toxin B (ETB), was determined. A total of 5 0 open reading frames were identified on the plasmid genome and, among thes e, 32 showed sequence similarity to known proteins. pETB contains three cop ies of IS257, which divide the pETB genome into three regions: (i) a cadmiu m resistance operon-containing region, (ii) a lantibiotic production gene-c ontaining region, and (iii) the remaining part where genes for plasmid repl ication and/or maintenance are dispersed. In the third region, genes of var ious kinds of functions are present among the replication- and maintenance- related genes. They include two virulence-related genes, the ctb gene and a gene encoding a novel ADP-ribosyltransferase closely related to EDIN, whic h belongs to the C3 family of ADP-ribosyltransferases modifying Rho GTPases . They also include genes for a cell wall-anchoring surface protein and a p hage resistance protein. Based on the determined sequence of pETB, the geno me structures of etb-bearing plasmids (ETB plasmids) from various clinical isolates were analyzed by the PCR scanning method. The data indicate that, although the ETB plasmids are highly heterogeneous in genome size, the fund amental genome organization is well conserved. The size variation of the pl asmid is mainly attributed to defined regions which may be hot spots for ge ne shuffling.