Outcomes of Acinetobacter baumannii infection in critically ill surgical patients

Multi-drug resistant (MDR) organisms in intensive care units (ICUs) are a growing concern. The emergence of several infections with MDR Acinetobacter baumannii prompted a review of cases and evaluation of the efficacy of intervention.

To determine the rate of clinical cure, the incidence of drug resistance, and the mortality rate associated with A. baumannii infection.

Retrospective review of A. baumannii infections in three surgical ICUs between January, 2004 and November, 2005. Infection was identified in 291 patients, 20 of whom were excluded because of incomplete documentation. Of the remaining 271 patients, 71% were male, and the mean age was 47 +/- 18 years (range 13-90 years).

Patients had a mean length of stay in the ICU of 14 days (range 0-136 days) before infection. The initial positive cultures were from bronchoalveolar lavage fluid (BAL) in 72.3%, blood in 16.2%, a catheter tip in 6.3%, urine in 1.8%, wound in 2.2%, and abscess in 1.1%. In 46.9% of patients, the first culture was polymicrobial. The Acinetobacter isolates were resistant or intermediate-resistant to imipenem-cilastatin in 81.2% of cases; 19.9% were resistant to all drugs except colistin, and two were resistant to all tested drugs. Colistin was used in 75.6% of patients (intravenous 61.5%, nebulized 38.5%). The mean duration of treatment was 13 +/- 8.9 days (range 0-56 days), and clinical cure was achieved in 73.8% of patients. Recurrent infection after initial cure was found in 19.2% of patients. There was no significant difference in clinical cure rates between patients treated with colistin and those treated with other culture-directed drugs (75.1% vs. 69.7%), or between patients treated with intravenous vs. nebulized colistin (72.4% vs. 79.5%). The mortality rate was 26.2% for the entire group and was significantly higher in the subgroup of transplant patients (n = 31) (64.5% vs. 21.4%; p < 0.001).

The majority of A. baumannii isolates were MDR, and a significant proportion were sensitive only to colistin. Treatment of A. baumannii infection with colistin is effective by both intravenous and nebulized routes of administration. However, infection with A. baumannii in critically ill surgical patients is associated with a high mortality rate, particularly in transplant patients.