Increased high-level gentamicin resistance in invasiveEnterococcus faeciumis associated withaac(6′)Ie-aph(2″)Ia-encoding transferable megaplasmids hosted by major hospital-adapted lineages

Abstract

Gentamicin is important in synergistic bactericidal therapy with cell wall agents for severe enterococcal infections. During 2003-2008, a 10-fold increase in the prevalence of high-level gentamicin resistance (HLGR), to above 50%, in blood culture isolates of Enterococcus faecium, was reported by the Norwegian Surveillance System for Antimicrobial Resistance. A representative national collection of invasive E. faecium isolates (n = 99) from 2008 was examined by a multilevel approach. Genotyping revealed a polyclonal population dominated by major hospital-associated lineages (mainly ST203, ST17, ST18, ST202 and ST192). The presence of aac(6')-Ie-aph(2″)-Ia, encoding the bi-functional aminoglycoside-modifying enzyme, was found in 98% of HLGR isolates (56/57). Furthermore, a significantly higher prevalence of potential virulence genes, toxin-antitoxin loci as well as pRE25 and pRUM type replicons was demonstrated in isolates belonging to major hospital-associated lineages compared to other sequence types. Megaplasmids of pLG1 replicon type (200-330 kb) were present in 90% of the isolates. Co-hybridization analyses revealed genetic linkage of aac(6')-Ie-aph(2″)-Ia to this replicon type. Transfer of HLGR-encoding plasmids was restricted to E. faecium. In conclusion, the increased prevalence of HLGR in invasive E. faecium in Norway is associated with hospital-adapted genetic lineages carrying aac(6')-Ie-aph(2″)-Ia-encoding transferable megaplasmids of the pLG1 replicon type.

Drug-resistant and hospital-associated Enterococcus faecium from wastewater, riverine estuary and anthropogenically impacted marine catchment basin

“…The same study also reported the co-localization of ω -ε-ζ with rep2 pRE25 and axe-txe with rep17 pRUM on the same plasmids, in concordance with our findings, showing a frequent joint occurrence of these pairs of genes. Another study, performed on 99 invasive isolates from Norway, mostly of HLGR phenotype, showed a significantly higher prevalence of rep2 pRE25 and rep17 pRUM among the major nosocomial HiRECC [38]. This study as well some others [24,39] also demonstrated a common presence of rep pLG1 among E. faecium from hospital settings and in animals .…”

Phage ϕC2 Mediates Transduction of Tn 6215 , Encoding Erythromycin Resistance, between Clostridium difficile Strains

“…The ω-ε-ζ system, together with δ and erm (B), was originally described in pSM19035 (31), a multidrug resistance-encoding plasmid from Streptococcus pyogenes . This TAS is important for plasmid maintenance (31–33), has homologues in Gram-positive and Gram-negative bacteria, and is associated with antibiotic-resistant strains of Enterococcus faecium and methicillin-resistant S. aureus (MRSA) (34, 35). However, the toxin gene (ζ) in Tn 6215 is truncated and is predicted to encode only 52/287 amino acids of the complete ζ in pSM19035.…”

A Multicentre Hospital Outbreak in Sweden Caused by Introduction of a vanB2 Transposon into a Stably Maintained pRUM-Plasmid in an Enterococcus faecium ST192 Clone

“…Consecutive hybridisation was performed using rep 17 / pRUM , vanB and axe-txe probes in the mentioned order. Characterisation of the rep pLG1 [35] and rep 2/pRE25 [36] plasmid determinants were also done by Southern blotting and hybridisation after S1-nucelase PFGE. Probes were made by amplification using positive controls (see Table S1), and labelled using the PCR DIG synthesis kit (Boehringer Mannheim).…”