title: Vancomycin-resistant Enterococcus spp.: validation of susceptibility testing and in vitro activity of vancomycin, linezolid, tigecycline and daptomycin.
abstract: Vancomycin-resistant enterococci (VRE) have emerged to become a significant nosocomial pathogen. However, detection may be challenging and treatment possibilities are limited. Reports of resistance to linezolide, daptomycin and tigecycline underline the need for reliable susceptibility testing with respect to these compounds. We evaluated the in vitro activity of vancomycin, linezolid, daptomycin and tigecycline against a panel of VRE and vancomycin-susceptible enterococci by broth microdilution (BMD). Etest for determination of minimum inhibitory concentration of these four antibiotics and two disc diffusion assays for detecting VRE and for susceptibility testing against tigecycline and linezolid were evaluated. Before susceptibility testing, all isolates were classified by polymerase chain reaction as vanA or vanB gene positive or vanA/B gene negative. Linezolid, daptomycin and tigecycline had excellent in vitro activity towards all isolates. For daptomycin and tigecycline, the overall agreement between BMD and Etest was suboptimal. For both disc diffusion assays, use of current break points was inadequate to detect vancomycin resistance for isolates carrying the vanB gene. Inspection of the inhibition zone for a diffuse edge, as recommended, accurately predicted presence of the vanB gene.
authors.affiliation: Department of Clinical Microbiology, Herning Regional Hospital, Herning, Denmark. mathias@rathe.nu
authors.forename: Mathias
authors.initials: M
authors.lastname: Rathe
authors.forename: Lise
authors.initials: L
authors.lastname: Kristensen
authors.forename: Svend
authors.initials: S
authors.lastname: Ellermann-Eriksen
authors.forename: Marianne Kragh
authors.initials: MK
authors.lastname: Thomsen
authors.forename: Helga
authors.initials: H
authors.lastname: Schumacher
mesh_terms: D000081:Acetamides / Q000494:pharmacology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics; D019729:Carbon-Oxygen Ligases / Q000737:chemistry / Q000235:genetics; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D017576:Daptomycin / Q000494:pharmacology; D013293:Enterococcus faecalis / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development; D016984:Enterococcus faecium / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development; D016908:Gram-Positive Bacterial Infections / Q000378:metabolism; D006801:Humans; D000069349:Linezolid; D008826:Microbial Sensitivity Tests / Q000379:methods*; D008911:Minocycline / Q000031:analogs & derivatives / Q000494:pharmacology; D023303:Oxazolidinones / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D015203:Reproducibility of Results; D000078304:Tigecycline; D014640:Vancomycin / Q000494:pharmacology; D020713:Vancomycin Resistance
chemical_list: D000081:Acetamides; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D023303:Oxazolidinones; C071437:VanA ligase, Bacteria; C079913:VanB protein, Enterococcus; D014640:Vancomycin; D000078304:Tigecycline; D019729:Carbon-Oxygen Ligases; D008911:Minocycline; D000069349:Linezolid; D017576:Daptomycin