title: Risk factors associated with ampicillin resistance in patients with bacteraemia caused by Enterococcus faecium.
abstract: Epidemiological characteristics of ampicillin-resistant, vancomycin-susceptible Enterococcus faecium are not well known. Recently, these strains have been proposed as the substratum for the later appearance of vancomycin-resistant E. faecium. To analyse this problem, the medical charts of patients with bacteraemia caused by E. faecium diagnosed in our institution during a 6 year period (1994-1999) were reviewed. Demographic data, clinical characteristics, antibiotic exposure and outcome were compared among patients with ampicillin-resistant (MIC > 16 mg/L, NCCLS criteria) and ampicillin-susceptible strains. Clonality between different strains was analysed by pulsed-field gel electrophoresis (PFGE). We evaluated 49 cases of E. faecium bacteraemia; 29 patients with ampicillin-resistant strains and 20 patients with -susceptible strains were identified. By logistic regression analysis, only previous administration of beta-lactams (OR: 6.3; 95% CI: 1.12-20.0) and urinary catheterization (OR:4.2; 95% CI: 1.3-30.0) were identified as predictors of ampicillin resistance in enterococcal bacteraemic patients. An elevated APACHE II score was the only independent factor associated with mortality in enterococcal bacteraemia (OR:13.5; 95% CI: 1.04-175.4). PFGE analysis revealed a strong association between specific ampicillin-resistant clones and the location of patients during hospitalization, suggesting nosocomial transmission. Bacteraemia caused by ampicillin-resistant enterococci was not associated with increased mortality when compared with bacteraemias caused by ampicillin-susceptible strains.
authors.affiliation: Department of Infectious Diseases, Ramón y Cajal Hospital, University of Alcalá, Crtra Colmenar Km 9.1, Madrid 28034, Spain. fortun@mi.madritel.es
authors.forename: Jesús
authors.initials: J
authors.lastname: Fortún
authors.forename: Teresa M
authors.initials: TM
authors.lastname: Coque
authors.forename: Pilar
authors.initials: P
authors.lastname: Martín-Dávila
authors.forename: Leonor
authors.initials: L
authors.lastname: Moreno
authors.forename: Rafael
authors.initials: R
authors.lastname: Cantón
authors.forename: Elena
authors.initials: E
authors.lastname: Loza
authors.forename: Fernando
authors.initials: F
authors.lastname: Baquero
authors.forename: Santiago
authors.initials: S
authors.lastname: Moreno
mesh_terms: D000668:Ampicillin Resistance; D000900:Anti-Bacterial Agents / Q000009:adverse effects / Q000627:therapeutic use; D016470:Bacteremia / Q000188:drug therapy* / Q000382:microbiology; D016009:Chi-Square Distribution; D016001:Confidence Intervals; D016984:Enterococcus faecium / Q000187:drug effects* / Q000302:isolation & purification; D006801:Humans; D007769:Lactams; D016015:Logistic Models; D015999:Multivariate Analysis; D016017:Odds Ratio; D012189:Retrospective Studies; D012307:Risk Factors; D014546:Urinary Catheterization / Q000009:adverse effects
chemical_list: D000900:Anti-Bacterial Agents; D007769:Lactams