title: Comparative activity of oritavancin against meticillin-resistant Staphylococcus aureus (MRSA) bloodstream isolates from Geneva University Hospital.
abstract: In this study, we assessed by broth microdilution the in vitro activity of oritavancin, a semisynthetic lipoglycopeptide currently under development, against selected meticillin-resistant Staphylococcus aureus (MRSA) bloodstream isolates (n=56) from Geneva University Hospital, Switzerland, displaying a wide range of vancomycin minimum inhibitory concentrations (MICs) (0.25-4 microg/mL). The MRSA resistance phenotype was confirmed by broth microdilution (oxacillin MIC > or = 4 microg/mL) for all isolates; 89% and 100% of the tested isolates were also resistant to erythromycin and ciprofloxacin, respectively. For 53 MRSA isolates for which vancomycin MICs were in the susceptible range (0.5-2.0 microg/mL), the oritavancin MICs ranged from 0.03 microg/mL to 0.5 microg/mL. For these 53 vancomycin-susceptible isolates, the cumulative distribution of oritavancin MICs was markedly different from those of vancomycin, teicoplanin, daptomycin and linezolid MICs, yielding an oritavancin MIC for 90% of the organisms (MIC(90)) (0.25 microg/mL) that was four times lower than the MIC(90) values (1 microg/mL) of comparators. For three MRSA isolates with a vancomycin-intermediate phenotype (vancomycin MIC=4 microg/mL), oritavancin MICs (0.5-1.0 microg/mL) were 2-4-fold lower than vancomycin, teicoplanin or daptomycin MICs, but were equivalent to linezolid MICs. Pairwise comparison for each bloodstream isolate showed that oritavancin was > or =4-fold more active than vancomycin, teicoplanin and daptomycin, against 86%, 75% and 59% of all MRSA isolates, respectively.
authors.affiliation: Service of Infectious Diseases, University Hospitals of Geneva, Geneva 14, Switzerland. Pierre.Vaudaux@hcuge.ch
authors.forename: Pierre
authors.initials: P
authors.lastname: Vaudaux
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Huggler
authors.forename: Francis F
authors.initials: FF
authors.lastname: Arhin
authors.forename: Gregory
authors.initials: G
authors.lastname: Moeck
authors.forename: Adriana
authors.initials: A
authors.lastname: Renzoni
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Lew
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D016470:Bacteremia / Q000382:microbiology*; D002939:Ciprofloxacin / Q000494:pharmacology; D004917:Erythromycin / Q000494:pharmacology; D006020:Glycopeptides / Q000494:pharmacology*; D006784:Hospitals, Teaching; D006801:Humans; D000077427:Lipoglycopeptides; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects* / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests; D013203:Staphylococcal Infections / Q000382:microbiology*; D013557:Switzerland; D014640:Vancomycin / Q000494:pharmacology / Q000031:analogs & derivatives
chemical_list: D000900:Anti-Bacterial Agents; D006020:Glycopeptides; D000077427:Lipoglycopeptides; D002939:Ciprofloxacin; D004917:Erythromycin; D014640:Vancomycin; C100708:oritavancin