Acinetobacter baumannii Infections in a Surgical Intensive Care Unit: Predictors of Multi-drug Resistance

OBJECTIVES: This study was designed to evaluate Acinetobacter baumannii infections incidence in our Surgical Intensive Care Unit, clinical features and outcome of these patients, and multi-resistance incidence to identify predictors of such a resistance. METHODS: Prospective study of all patients with ICU-acquired Acinetobacter baumannii infection from June 1, 2003 to May 31, 2005. Patients with multi-resistant infection, susceptible exclusively to colistin, were compared with those sustaining non-multi-drug resistant infection. RESULTS: Among 411 patients, 52 (12.6%) developed Acinetobacter infection. Their mean age was 66.3 +/- 8.4 years and APACHE II 20.4 +/- 7.3 (men: 51.9%). Infection sites were: bloodstream (46.2%), respiratory tract (32.7%), central venous catheter (11.5%), surgical site (7.7%), and urinary tract (1.9%). High multi-resistance (44.2%), morbidity (63.4%), and mortality (44.2%) were identified. Colistin was the most effective antibiotic (100% susceptibility), whereas resistance against all other antibiotics was >60%. Previous septic shock (p = 0.04), previous adult respiratory distress syndrome (ARDS) (p = 0.01), number of previous antibiotics (p = 0.01), previous aminoglycoside use (p = 0.04), and reoperation (p = 0.01) were risk factors for multi-resistance in univariate analysis. Morbidity in the multi-resistant group was significantly higher than the non-multi-resistant group (82.6% vs. 48.2%, p = 0.02). Mortality in the multi-resistant group also was higher; however, this difference did not marginally reach statistical significance (60.8% vs. 31.1%, p = 0.06). Multivariate analysis identified previous septic shock (p = 0.04; odds ratio (OR), 9.83; 95% confidence interval (CI), 1.003-96.29) and reoperation (p = 0.01; OR, 8.45; 95% CI, 1.52-46.85) as independent predictors of multi-resistance. CONCLUSION: Acinetobacter baumannii infections are frequent and associated with high morbidity, mortality, and multi-resistance. Avoidance of unnecessary antibiotics is a high priority, and specific attention should be paid to patients with previous ARDS and, particularly, previous septic shock and reoperation. When such risk factors are identified, colistin may be the only appropriate treatment.