Characterization of Two Newly Identified Genes, vgaD and vatG , Conferring Resistance to Streptogramin A in Enterococcus faecium

Abstract

We characterized two new streptogramin A resistance genes from quinupristin-dalfopristin-resistant Enterococcus faecium JS79, which was selected from 79 E. faecium isolates lacking known genes encoding streptogramin A acetyltransferase. A 5,650-bp fragment of HindIII-digested plasmid DNA from E. faecium JS79 was cloned and sequenced. The fragment contained two open reading frames carrying resistance genes related to streptogramin A, namely, genes for an acetyltransferase and an ATP efflux pump. The first open reading frame comprised 648 bp encoding 216 amino acids with a predicted left-handed parallel ␤-helix domain structure; this new gene was designated vatG. The second open reading frame consisted of 1,575 bp encoding 525 amino acids with two predicted ATPase binding cassette transporters comprised of Walker A, Walker B, and LSSG motifs; this gene was designated vgaD. vgaD is located 65 bp upstream from vatG, was detected together with vatG in 12 of 179 quinupristin-dalfopristin-resistant E. faecium isolates, and was located on the same plasmid. Also, the 5.6-kb HindIII-digested fragment which was observed in JS79 was detected in nine vgaD-and vatG-containing E. faecium isolates by Southern hybridization. Therefore, it was expected that these two genes were strongly correlated with each other and that they may be composed of a transposon. Importantly, vgaD is the first identified ABC transporter conferring resistance to streptogramin A in E. faecium. Pulsed-field gel electrophoresis patterns and sequence types of vgaD-and vatG-containing E. faecium isolates differed for isolates from humans and nonhumans.

Intrinsic and acquired resistance mechanisms in enterococcus

“…VgaD has been described only in E. faecium . vgaD was found on a plasmid with vatH , both of which confer only streptogramin A resistance 92 . To date, no other acquired streptogramin efflux pumps have been described.…”

Current Trends of Emergence and Spread of Vancomycin-Resistant Enterococci

“…Their relevance for increasing the level of streptogramin resistance in E. faecalis is unclear; nevertheless, resistance determinants could further spread to E. faecium and other enterococcal species thus rendering their level of streptogramin susceptibility. Staphylococcal efflux pumps of the Vga-type encoding for streptogramin type A resistance remain unknown to E. faecium (Werner et al, 2002); except for a single Korean E. faecium isolate described recently harbouring streptogramin A resistance genes vgaD and vatG on a plasmid fragment encoding for a new efflux pump type and a new streptogramin acetyltransferase, respectively (Jung et al, 2010).…”

Gida Kaynakli Enterokoklarin Potansi̇yel Ri̇sk Faktörleri̇

“…Kinolonlara karfl› gözlenen üçüncü direnç mekanizmas› ise efluks pompalar› ile antibiyoti¤in hücre d›fl›na at›lmas›d›r. EmeA (45) …”