Chromosome- and plasmid-mediated gentamicin resistance in Staphylococcus aureus encoded by Tn4001

Abstract

Summary DNA sequences corresponding to the 4·7-kb gentamicin, tobramycin and kanamycin resistance (Gmr Tmr Kmr) transposon Tn4001 have been detected on a series of nine structurally-related plasmids that mediate this phenotype in Australian isolates of Staphylococcus aureus. Tn4001 sequences have also been demonstrated on the chromosomes of GmTmr Kmr isolates that do not possess these plasmids, and the exhibited diversity of chromosomal sites occupied by this element implies that Tn4001 has transposed to the chromosome on numerous occasions in vivo. These results suggest that the rapid emergence of nosocomial Gmr Tmr Kmr S. aureus in the early 1980s may have been the result of the transposition of Tn4001 from a chromosomal site to a readily disseminated plasmid.