title: Characterization of vancomycin-resistant Enterococcus faecium isolates from the United States and their susceptibility in vitro to dalfopristin-quinupristin.
abstract: In the course of clinical studies with the investigational streptogramin antimicrobial dalfopristin-quinupristin, isolates of vancomycin-resistant Enterococcus faecium were referred to our laboratory from across the United States. Seventy-two percent of the strains were of the VanA type, phenotypically and genotypically, while 28% were of the VanB type. High-level resistance to streptomycin or gentamicin was observed in 86 and 81%, respectively, of the VanA strains but in only 69 and 66%, respectively, of the VanB strains. These enterococci were resistant to ampicillin (MIC for 50% of the isolates tested [MIC50] and MIC90, 128 and 256 microg/ml, respectively) and to the other approved agents tested, with the exception of chloramphenicol (MIC90, 8 microg/ml) and novobiocin (MIC90, 1 microg/ml). Considering all of the isolates submitted, dalfopristin-quinupristin inhibited 86.4% of them at concentrations of < or = 1 microg/ml and 95.1% of them at < or = 2 microg/ml. However, for the data set comprised of only the first isolate submitted for each patient, 94.3% of the strains were inhibited at concentrations of < or = 1 microg/ml and 98.9% were inhibited at concentrations of < or = 2 microg/ml. Multiple drug resistance was very common among these isolates of vancomycin-resistant E. faecium, while dalfopristin-quinupristin inhibited the majority at concentrations that are likely to be clinically relevant.
authors.affiliation: Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts 02215, USA. geliopou@bidmc.harvard.edu
authors.forename: G M
authors.initials: GM
authors.lastname: Eliopoulos
authors.forename: C B
authors.initials: CB
authors.lastname: Wennersten
authors.forename: H S
authors.initials: HS
authors.lastname: Gold
authors.forename: T
authors.initials: T
authors.lastname: Schülin
authors.forename: M
authors.initials: M
authors.lastname: Souli
authors.forename: M G
authors.initials: MG
authors.lastname: Farris
authors.forename: S
authors.initials: S
authors.lastname: Cerwinka
authors.forename: H L
authors.initials: HL
authors.lastname: Nadler
authors.forename: M
authors.initials: M
authors.lastname: Dowzicky
authors.forename: G H
authors.initials: GH
authors.lastname: Talbot
authors.forename: R C
authors.initials: RC
authors.lastname: Moellering
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004352:Drug Resistance, Microbial; D016984:Enterococcus faecium / Q000187:drug effects* / Q000302:isolation & purification / Q000378:metabolism; D006801:Humans; D008826:Microbial Sensitivity Tests; D014481:United States; D014640:Vancomycin / Q000494:pharmacology; D014769:Virginiamycin / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D014769:Virginiamycin; C062940:quinupristin-dalfopristin; D014640:Vancomycin