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

Abstract A new staphylococcal composite transposon, designated Tn 5405, carrying the genes aphA-3 and aadE, 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 IS 1182. This insertion sequence is 1864 bp long and has 23/33-bp imperfect inverted repeats at its ends. One of the IS 1182 copies delimiting Tn 5405 contains a copy of IS 1181 flanked by 8-bp direct repeats. Tn 5405 was found in the chromosome of MRSA clinical isolate BM3121, within a Tn 552 -related transposon, Tn 5404. Tn 5404 was 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 Tn 5405 within Tn 5404 were detected. IS 1182 was not detected in the DNA of 4 of the 17 tested MRSA isolates containing aphA-3 and resistant to streptomycin. Thus, aphA-3 and aadE genes are not disseminated only by Tn 5405 or related transposons delimited by IS 1182.