Attributable mortality of nosocomial Acinetobacter Bacteremia

OBJECTIVE. To determine the attributable mortality and outcome of nosocomial Acinetobacter bacteremia. DESIGN. Matched, retrospective cohort study. SETTING. Large, university- based, tertiary care center. PATIENTS. Of 219 patients with nosocomial Acinetobacter bacteremia identified by prospective surveillance during a 3- year period, 52 met the criteria for the study and were matched to a control patient by age, sex, primary and secondary diagnosis, operative procedures, and date of admission. RESULTS. A 100% success rate was achieved in the proportion of case patients and control patients matched for the compared criteria, except for major operative procedures ( 88%) and the presence of an important secondary underlying disease ( 54.5%). Twenty- nine ( 55.7%) of the case patients died, compared with 10 ( 19.2%) of the control patients (). The attributable mortality was 36.5% ( 95% CI, 27%- 46%) and the risk ratio for death was 2.9 ( 95% CI, 1.58- 5.32). In a multivariate survival analysis, older age, mechanical ventilation, renal failure, and Acinetobacter bacteremia ( hazard ratio [ HR], 4.41; 95% confidence interval [ CI], 1.97- 9.87; P<.001) were found to be independent predictors of mortality. There was a trend for a longer median duration of hospitalization among case patients, compared with control patients ( 11.5 vs. 6.5 days; Pp=.06). Three isolates were resistant to all but 1 antibiotic tested ( colistin), and 45 isolates ( 86.5%) were resistant to 4 or more different antibiotic classes. CONCLUSIONS. When adjusted for risk- exposure time and severity of disease at admission, nosocomial Acinetobacter bacteremia is associated with mortality in excess of that caused by the underlying diseases alone.