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.

Links

Publisher Full Text

Authors

Rosvoll TC, Lindstad BL, Lunde TM, Hegstad K, Aasnaes B, Hammerum AM, Lester CH, Simonsen GS, Sundsfjord A, Pedersen T

Institution

Research Group for Host-Microbe Interactions, Department of Medical Biology, Faculty of Health Sciences, University of Tromsø, Tromsø, Norway.

Source

FEMS immunology and medical microbiology 66:2 2012 Nov pg 166-76

MeSH

Acetyltransferases
Anti-Bacterial Agents
Cross Infection
Drug Resistance, Bacterial
Enterococcus faecium
Genotype
Gentamicins
Gram-Positive Bacterial Infections
Hospitals
Humans
Molecular Typing
Norway
Phosphotransferases (Alcohol Group Acceptor)
Plasmids

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

22672387