Evaluation of outcome in critically ill patients with Acinetobacter baumanniibacteremia

Objective

Bacteremia caused by Acinetobacter baumannii has an increasing incidence among critically ill patients. However, it is not clear whether it is associated with a higher mortality since controversial results have been reported. Increased mortality rate has been shown in some studies [1], whereas in others A. baumannii bacteremia does not alter the outcome [2]. The aim of this study was to evaluate the clinical impact of A. baumannii bacteremia on the outcome of patients in our ICU.

Patients and methods

During a 4-month period (August–December 2004), in a 30-bed multidisciplinary ICU, patients who developed A. baumannii bacteremia and control patients without microbiological evidence of bacteremia were prospectively studied. Matching of control patients (1:2 ratio) was made on the basis of the APACHE II score (± 2 points) and diagnostic category.

Results

During the study period, A. baumannii bacteremia was diagnosed in 21 patients (59 ± 15 years, mean ± standard deviation), admitted to the ICU (incidence 9.3 per 100 admissions). The APACHE II score in case and control patients was 19.9 ± 4.5 and 19.6 ± 4.8, respectively. The median interval from admission to the A. baumannii bacteremia was 10.5 days. A. baumanii strains were resistant to all antibiotics but susceptible to imipenem/cilastin and colistin. The ICU length of stay was 37 (23–51) days and 9 (1.8–16.2) days, median (95% confidence interval), for case and control patients, respectively, P < 0.001. Case patients had a longer duration of mechanical ventilation versus control: 21 (9–53) days versus 5 (2–18) days, respectively, P < 0.001. No differences between case and control patients were found in gender and age. Patients with A. baumannii bacteremia had significantly higher mortality than controls (38.1% vs 7.15%, P = 0.004). Logistic regression analysis showed that risk factors that were independently associated with adverse outcome were the presence of bacteremia (odds ratio = 10.2, P = 0.013), and multisystem organ failure (odds ratio = 20.9, P = 0.001).

Conclusions

In this group of critically ill patients, after adjustment for severity of acute illness, A. baumannii bacteremia was associated with a significantly increased mortality rate compared with matched control patients. Whether other factors contribute to this increase has to be examined.