Chromosome- and plasmid-mediated gentamicin resistance in Staphylococcus aureus encoded by Tn4001

Plasmid-encoded resistance to the aminoglycosides gentamicin (Gm), tobramycin (Tm), and kanamycin (Km) (GmTmKmr) In Australian strains of Staphylococcus aureus, resistance to the aminoglycosides gentamicin, tobramycin, and kanamycin (GmTmKmr) has been shown to be encoded on a transposon, Tn4001 (17,18). This composite transposon consists of two inverted copies of the 1.3-kb insertion sequence IS256 flanking a 1.9-kb unique region (5, 17, 24). The resistance aacA-aphD gene is contained within the unique region and codes for production of a 56.9-kDa bifunctional enzyme that specifies aminoglycoside-modifying acetyltransferase AAC(6') and phosphotransferase APH(2") activities (24).Tn4001 is commonly found on members of the pSK1 family of multiresistance plasmids (9,18,28). The majority of these plasmids mediate resistance to acriflavine, ethidium bromide, and quaternary ammonium compounds determined by the qacA gene (31,32). In addition, pSK1-type plasmids may confer resistance to penicillin via production of a P-lactamase carried on Tn4002 (10) and high-level resistance to trimethoprim mediated by a trimethoprim-insensitive dihydrofolate reductase encoded on the putative transposon Tn4003 (25).GmTmKmr in clinical strains of staphylococci from North America is frequently mediated by a group of structurally related plasmids unrelated to the pSK1 family of plasmids found in Australian clinical strains of staphylococci. Many of these plasmids are conjugative (2, 3, 22) and, in addition to GmTmKmr, can specify resistance to other aminoglycosides through 4'-adenyltransferase or 3'-phosphotransferase activities, and they may also mediate resistance to ethidium bromide and quaternary ammonium compounds, penicillin, and trimethoprim (1,2,11,12,14,22 pUW3626 and the related but nonconjugative plasmid pSH6 were isolated from North American clinical strains of S. aureus. Previous molecular studies indicated that these plasmids contained the same GmTmKmr determinant as found in Tn4001 (15). Like Tn4001, the resistance determinants in these plasmids were shown to be flanked by inverted repeats. Although these repeats shared some homology with IS256, they were significantly shorter than the 1.3-kb inverted IS256 elements on Tn400J (15,18,28 (4,25,26). Furthermore, IS257 elements share a significant degree of similarity in both their nucleotide and putative transposase aa sequences with members of the ISI5

Section: Discussionmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

See 1 more Smart Citation

Molecular analysis of a gentamicin resistance transposonlike element on plasmids isolated from North American Staphylococcus aureus strains

Byrne

Gillespie

Skurray

1990

“…4 for further details). Tn400J and Tn4031 contain symmetrically located HindIII sites (2.5 kb apart) and symmetrically located ClaI sites (-2.5 kb apart) positioned just outside of the HindIlI sites (12,15,21). Tn400J also has two HaeIII sites located 0.35 kb apart that are positioned near the outer terminus of each IS256 element (16); the inner HaeIII sites are symmetrically located 3.9 kb apart (HaeIII recognition sites have not been published for Tn4031).…”

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confidence: 99%

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

Hodel-Christian¹,

Murray²

1991

106

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.

“…Tn4001 is a composite transposon that has a 2.0-kilobase-pair (kb) region encoding aacA-aphD bounded by 1.35-kb terminal inverted repeats (IS256), for a total length of 4.7 kb (14,15). Symmetrically located HindIII (2.5-kb) and HaeIII (3.9-kb) fragments are found in Tn4001 (11,16). The 2.5-kb HindIIl fragment has been shown to hybridize with a 2.5-kb HindIII fragment in plasmids found in North American isolates of Gmr S. aureus (14).…”

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confidence: 99%

Mobilization of the gentamicin resistance gene in Enterococcus faecalis

Hodel-Christian

Murray

1990

Enterococcus faecalis plasmid pBEM10 (a conjugative plasmid encoding beta-lactamase production and gentamicin resistance [Gmr]) was made transfer deficient by using Tn917. Relocation of the Gmr determinant into two sites on pCF10 was observed. Restriction analysis revealed insertion of a common 2.5-kilobase-pair HindIII and a 3.9-kilobase-pair HaeIII fragment encoding Gmr, suggesting that this determinant resides on a transposon similar to Tn4001.