Characterization of aStaphylococcus aureusTransposon, Tn5405,Located within Tn5404and Carrying the Aminoglycoside Resistance Genes,aphA-3andaadE

A new staphylococcal composite transposon, designated Tn5405,carrying the genesaphA-3andaadE,which encode resistance to aminoglycosides, was partially characterized. The transposon is 12 kb long and is flanked by inverted repeated sequences displaying the characteristic features of an insertion sequence, named IS1182.This insertion sequence is 1864 bp long and has 23/33-bp imperfect inverted repeats at its ends. One of the IS1182copies delimiting Tn5405contains a copy of IS1181flanked by 8-bp direct repeats. Tn5405was found in the chromosome of MRSA clinical isolate BM3121, within a Tn552-related transposon, Tn5404.Tn5404was previously characterized following its transposition onto a β-lactamase plasmid harbored by BM3121. Two forms of the recombinant β-lactamase-encoding plasmid generated by the inversion of Tn5405within Tn5404were detected. IS1182was not detected in the DNA of 4 of the 17 tested MRSA isolates containingaphA-3and resistant to streptomycin. Thus,aphA-3andaadEgenes are not disseminated only by Tn5405or related transposons delimited by IS1182.