Characterization of the gentamicin resistance transposon Tn5281 from Enterococcus faecalis and comparison to staphylococcal transposons Tn4001 and Tn4031

Abstract

In Enterococcus faecalis, the genetic determinant encoding gentamicin resistance (Gm') on the conjugative plasmid pBEMIO previously has been shown to be on a mobile element. In the current study, this element, termed TnS281, was shown to relocate in the absence of homologous recombination in E. faecalis UV202. On the basis of restriction endonuclease analysis and DNA-DNA hybridization studies, Tn5281 was shown to be similar, if not identical, to the Gmr transposons Tn4001 found in Australian isolates of Staphylococcus aureus and Tn4031 found in U.S. isolates of Staphylococcus epidermidis, since all three of these transposons have symmetrically located HindIll (2.5 kb apart), ClaI (slightly more than 2.5 kb apart), and HaeIII (3.9 kb apart) sites. Restriction endonuclease digestion patterns of Tn5281 generated with HincII, ScaI, and AluI were also consistent with Tn4001 and Tn4031. By using a probe specific for the external portion of the terminal inverted repeat of Tn4031, it was determined that each terminus of Tn5281 contained a 0.35-kb HaeIII fragment and a 0.7-kb HindIII-HaeIII fragment. The sizes of these fragments are identical to those found in the staphylococcal transposons, which is a further indication that inverted repeats like IS256 are present in Tn5281. A 1-kb HaeIII fragment in pBEMIO also hybridized with this probe, which indicates that Tn5281 in pBEM10 contains a double copy of the inverted repeat at one end.

Characterization of Tn 1546 in Vancomycin-Resistant Enterococcus faecium Isolated from Canine Urinary Tract Infections: Evidence of Gene Exchange between Human and Animal Enterococci

“…The aac6Ј-aph2Љ genes have, in most cases, been localized to plasmids. Studies by Hodel-Christian and Murray (17,18) identified the aac6Ј-aph2Љ gene as part of transposon Tn5281. Association of aac6Ј-aph2Љ with a transposon further aids in the rapid dissemination of the resistance marker.…”

Formation of potent hybrid promoters of the mutant llm gene by IS256 transposition in methicillin-resistant Staphylococcus aureus

“…In this case, transposition of IS256 independent of a transposon had not yet been observed. On the other hand, IS256 itself was present in multiple copies on the chromosome (9,22) and was observed to increase in copy number and to transpose independently of Tn4001 or the Tn4001-like element upon transformation or conjugation (21,26). Our preliminary Southern analysis also suggested that there are multiple copies of IS256 in most clinical isolates of MRSA and the parent strain, SRM551, and that its copy number increases in the llm mutant upon transformation (unpublished data).…”

“…IS256 was originally found flanking the aminoglycoside resistance determinant, yielding the composite transposon Tn4001 (14) or a Tn4001-like element (9,28). Both can transpose into various loci on the chromosome (12,16) and are involved in the dissemination of the resistance gene among staphylococci, enterococci, and streptococci (11,13,26).…”

Conjugative Plasmid Transfer in the Biofilm Formed by Enterococcus faecalis

“…This strain was used as a control in screening for highlevel aminoglycoside resistance in enterococci. 35) The aac(6′)-1 and aph(2′′) genes are plasmid borne in most gentamicin-resistant isolates of E. faecalis, 36,37) and conjugal transfer of aac(6′)-1 and aph(2′′) on the plasmid has been reported in enterococci. 36,38) Our experimental results indicated that strain ATCC51299 harbored the plasmids containing the EcoRI fragments indicated by the arrowheads in Fig.…”