COMPLETE NUCLEOTIDE-SEQUENCE OF PSK41 - EVOLUTION OF STAPHYLOCOCCAL CONJUGATIVE MULTIRESISTANCE PLASMIDS

The 46.4-kb nucleotide sequence of pSK41, a prototypical multiresistan ce plasmid from Staphylococcus aureus, has been determined, representi ng the first completely sequenced conjugative plasmid from a gramposit ive organism. Analysis of the sequence has enabled the identification of the probable replication, maintenance, and transfer functions of th e plasmid and has provided insights into the evolution of a clinically significant group of plasmids, The basis of deletions commonly associ ated,with pSK41 family plasmids has been investigated, as has the obse rved insertion site specificity of Tn552-like beta-lactamase transposo ns within them. Several of the resistance determinants carried by pSK4 1-like plasmids were found to be located on up to four smaller cointeg rated plasmids, pSK41 and related plasmids appear to represent a conso lidation of antimicrobial resistance functions, collected by a preexis ting conjugative plasmid via transposon insertion and IS257-mediated c ointegrative capture of other plasmids.