Characterization of transposon Tn1549, conferring VanB-type resistance in Enterococcus spp.

Transfer of VanB-type resistance to glycopeptides among enterococci has been reported to be associated with the movement of large chromosomal genetic elements or of plasmids. The authors report the characterization of the 34 kb transposon Tn1549 borne by a plasmid related to pAD1 and conferring vancomycin resistance in clinical isolates of Enterococcus spp. Tn1549 contained 30 ORFs and appeared to be organized like the Tn916 family of conjugative transposons into three functional regions: (i) the right end, implicated in the excision-integration process; (ii) the central part, in which the vanB2 operon replaces the tet(M) gene; and (iii) the left extremity, in which eight of the 18 ORFs could be implicated in the conjugative transfer.