Comparison of the gentamicin resistance transposon Tn5281 with regions encoding gentamicin resistance in Enterococcus faecalis isolates from diverse geographic locations

Abstract

The genetic determinant encoding gentamicin resistance (Gm(r)) on the β- lactamase encoding plasmid pBEM10 of Enterococcus faecalis HH22 is carried on a transposon, termed Tn5281, that is highly related to the staphylococcal Gm(r) transposons Tn4001 found in Australian isolates of Staphylococcus aureus and Tn4031 found in United States isolates of Staphylococcus epidermidis. We have now studied plasmid DNA from Gm(r) strains of E. faecalis isolated from diverse geographical locations (Houston, Pennsylvania, Thailand, and Chile) by using restriction endonuclease analysis and DNA-DNA hybridization to determine whether other Gm(r) E. faecalis carry Tn5281 or a similar type of element. We also compared these enterococci to several United States isolates of Staphylococcus aureus with nonmobile Gm(r) determinants. Three E. faecalis isolates (from Houston and Chile) carried Tn5281-like elements, whereas two isolates (from Houston and Pennsylvania) had restriction endonuclease and DNA-DNA hybridization patterns more similar to those of the Tn4001-IS257 hybrid found in the nonmobile Gm(r) determinants in United States isolates of S. aureus. A strain from Thailand had a third pattern unrelated to either Tn5281 or the nonmobile Gm(r) determinants present in United States isolates of S. aureus. Our results demonstrate that there is both similarity and diversity between the Gm(r) determinant of strains of E. faecalis isolated in diverse geographic locations.