title: Modified time-kill assay against multidrug-resistant Enterococcus faecium with novel antimicrobial combinations.
abstract: This study used a modified time-kill assay to compare the in-vitro activity of chloramphenicol and quinopristin/dalfopristin combined with vancomycin, ampicillin or gentamicin against multidrug-resistant Enterococcus faecium. The assay uses standardized time-kill methods with the following modifications: centrifugation of the test tubes at 1-2 h intervals, removal of supernatant and resuspension of bacteria in media containing antibiotic concentrations corresponding to simulated steady-state serum concentrations. None of the agents, alone or in combination, produced bactericidal or synergic activity. The modified time-kill assay more closely simulates in-vivo conditions and may provide a better qualitative assay to determine the interaction between antimicrobial agents and bacteria.
authors.affiliation: Department of Veterans Affairs, Cooperative Studies Program, Clinical Research Pharmacy Coordinating Center, 2401 Center Avenue SE, Albuquerque, NM 87106-4180, USA.
authors.forename: C R
authors.initials: CR
authors.lastname: Messick
authors.forename: K A
authors.initials: KA
authors.lastname: Rodvold
authors.forename: S L
authors.initials: SL
authors.lastname: Pendland
mesh_terms: D000667:Ampicillin / Q000494:pharmacology; D002701:Chloramphenicol / Q000494:pharmacology; D015169:Colony Count, Microbial; D004352:Drug Resistance, Microbial; D018432:Drug Resistance, Multiple; D004359:Drug Therapy, Combination / Q000494:pharmacology*; D016984:Enterococcus faecium / Q000187:drug effects* / Q000254:growth & development; D005839:Gentamicins / Q000494:pharmacology; D007700:Kinetics; D008826:Microbial Sensitivity Tests / Q000379:methods*; D013997:Time Factors; D014640:Vancomycin / Q000494:pharmacology; D014769:Virginiamycin / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D005839:Gentamicins; D014769:Virginiamycin; D002701:Chloramphenicol; D014640:Vancomycin; D000667:Ampicillin; C113826:dalfopristin