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.

References