Tn5384, a composite enterococcal mobile element conferring resistance to erythromycin and gentamicin whose ends are directly repeated copies of IS256

Abstract

We have identified a 26-kb mobile element from Enterococcus faecalis CH116, designated Tn5384, which confers resistance to erythromycin and to high levels of gentamicin. Tn5384 is a composite element containing three copies of insertion element IS256. Two of the IS256 copies flank the aac6-aph2؆ bifunctional aminoglycoside-modifying-enzyme gene in the inverted orientation, forming a structure similar to staphylococcal gentamicin resistance transposon Tn4001. One of the IS256 elements involved in the Tn4001-like structure also forms the left end of Tn5384, the right end of which is a directly repeated insertion of IS256 approximately 23 kb downstream of the leftmost insertion. Insertions of Tn5384 into enterococcal plasmid pLRM1 have been found associated with 8-and 9-bp duplications of the target sequence.

Essential genes of a minimal bacterium

“…We considered transposon insertions disruptive if they were after the first three codons and before the 3Ј-most 20% of the coding sequence of a gene. Thus, nondisruptive mutations resulting from transposon-mediated duplication of short sequences at the insertion site (15,16) and potentially inconsequential COOHterminal insertions do not result in erroneous determination of gene expendability. Using these criteria, we identified a total of 100 dispensable M. genitalium genes ( Table 2, which is published as supporting information on the PNAS web site).…”

In Vitro Antibacterial Activity of Vertilmicin and Its Susceptibility to Modifications by the Recombinant AAC(6′)-APH(2″) Enzyme

“…The two domains do not functionally interact but have intimate structural linkages that are important for con-formation and stability (5). The aac(6Ј)-aph(2Љ) genes can be found in both the R plasmids (6-7, 11, 30-33) and chromosomes (15,(26)(27)34) of aminoglycoside-resistant isolates, with locations on transposons, like Tn4001 (18), Tn4031 (35), and Tn5381 (14). In the present study, we cloned the aac(6Ј)-aph(2Љ) genes from E. faecalis HH22 (22) and expressed the enzyme in a recombinant strain of E. coli.…”

Structures,Locations, and Transfer Frequencies of Genetic Elements ConferringHigh-Level Gentamicin Resistance in Enterococcusfaecalis Isolates inGreece

“…Several variants of transposon Tn4001 have been identified in enterococci from diverse geographic locations; the transposon Tn5281, in which there is a tandem duplication of IS256 at one terminus of Tn4001 (7), the Tn4001-IS257 hybrid (7), and the Tn4001-truncated elements (3,8,19). Moreover, new transposable elements involved in the dissemination of gentamicin resistance have been described (15,16,21).…”