title: Bactericidal activity of oxacillin and glycopeptides against Staphylococcus aureus in patients with endocarditis: looking for a relationship between tolerance and outcome.
abstract: BACKGROUND
  There is no clear relationship between in vitro bactericidal activity tests and clinical outcome. We studied bactericidal activity of oxacillin, vancomycin and teicoplanin against Staphylococcus aureus isolates in patients with endocarditis and then we sought to determine if there was a relationship between in vitro bactericidal activity and clinical outcome.
  
  
  METHODS
  Minimal bacteriostatic and minimal bactericidal concentrations were determined for Staphylococcus aureus strains isolated from patients with endocarditis following standardized methods. Medical records were reviewed retrospectively to collect data on antimicrobial susceptibility at admission, antimicrobial therapy, need for surgery, embolic events and outcome.
  
  
  CONCLUSIONS
  Sixty-two Staphylococcus aureus strains were studied in 62 patients with endocarditis. Overall, 91.9% definite, 21% methicillin resistant and 72.6% cured. Surgery was performed in 32.3% and embolic events were documented in 64.5%. Tolerance to oxacillin and teicoplanin was more common than vancomycin tolerance among methicillin susceptible Staphylococcus aureus. Among methicillin resistant Staphylococcus aureus teicoplanin was shown to have a higher rate of tolerance than vancomycin. No statistically significant differences on clinical outcome between oxacillin tolerant and oxacillin non tolerant Staphylococcus aureus infections were observed. Tolerance to oxacillin did not adversely affect clinical outcomes of patients with methicillin susceptible Staphylococcus aureus endocarditis treated with a combination of antimicrobials including oxacillin. The cure rate was significantly lower among patients with methicillin resistant Staphylococcus aureus endocarditis.
  
  
  CONCLUSIONS
  In vitro bactericidal test results were not valid predictors of clinical outcome. Physicians need to use additional parameters when treating patients with staphylococcal endocarditis.
authors.affiliation: Section of Infectious Diseases, Department of Experimental Medicine and Biochemical Sciences, University of Perugia, Perugia, Italy. pasticci@unipg.it
authors.forename: Maria Bruna
authors.initials: MB
authors.lastname: Pasticci
authors.forename: Amedeo
authors.initials: A
authors.lastname: Moretti
authors.forename: Giuliano
authors.initials: G
authors.lastname: Stagni
authors.forename: Veronica
authors.initials: V
authors.lastname: Ravasio
authors.forename: Laura
authors.initials: L
authors.lastname: Soavi
authors.forename: Annibale
authors.initials: A
authors.lastname: Raglio
authors.forename: Francesca
authors.initials: F
authors.lastname: Vailati
authors.forename: Angela
authors.initials: A
authors.lastname: Cardaccia
authors.forename: Antonella
authors.initials: A
authors.lastname: Santucci
authors.forename: Rita
authors.initials: R
authors.lastname: Papili
authors.forename: Alessio
authors.initials: A
authors.lastname: Sgrelli
authors.forename: Carlo
authors.initials: C
authors.lastname: Pallotto
authors.forename: Franco
authors.initials: F
authors.lastname: Baldelli
mesh_terms: D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology / Q000627:therapeutic use*; D024881:Drug Resistance, Bacterial; D004359:Drug Therapy, Combination; D004697:Endocarditis, Bacterial / Q000188:drug therapy* / Q000382:microbiology; D005260:Female; D006020:Glycopeptides / Q000494:pharmacology / Q000627:therapeutic use*; D006801:Humans; D008297:Male; D010068:Oxacillin / Q000494:pharmacology / Q000627:therapeutic use*; D012189:Retrospective Studies; D015610:Serum Bactericidal Test; D013203:Staphylococcal Infections / Q000188:drug therapy* / Q000382:microbiology; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000302:isolation & purification; D016896:Treatment Outcome
chemical_list: D000900:Anti-Bacterial Agents; D006020:Glycopeptides; D010068:Oxacillin