Impact of multi-drug-resistant Acinetobacter baumannii on clinical outcomes

We conducted a retrospective matched cohort study to examine the impact of isolation of multi-drug-resistant (MDR) Acinetobacter baumannii on patient outcomes. Cases from whom MDR A. baumannii was isolated in a clinical culture (n=118) were compared with controls from whom MDR A. baumannii was not isolated (n=118). Cases and controls were matched according to ward, calendar month of hospitalization, and duration of hospitalization before culture. The following outcomes were compared in multivariable analysis: in-hospital mortality, length of stay, need for mechanical ventilation, and functional status at discharge. MDR A. baumannii was determined to be a pathogen in 72% of cases. In 36% of cases, the patient died, versus 21% of controls (odds ratio [OR] 2.21, 95% confidence interval [CI] 1.17-4.16, P=0.014). Median length of stay for surviving cases was 17 days, versus 11 for surviving controls (multiplicative effect 1.55, 95% CI 0.99-2.44, P=0.057). Fifty-two percent of cases required mechanical ventilation, versus 25% of controls (OR 3.72, 95% CI 1.91-7.25, P < 0.001); 60% of surviving cases were discharged with reduced functional status, versus 38% of controls (OR 4.4, 95% CI 1.66-11.61, P=0.003). In multivariable analysis, clinical isolation of MDR A. baumannii remained a significant predictor of mortality (OR 6.23, 95% CI 1.31-29.5, P=0.021), need for mechanical ventilation (OR 7.34, 95% CI 2.24-24.0, P < 0.001), and reduced functional status on discharge (OR 7.93, 95% CI 1.1-56.85, P=0.039). Thus, MDR A. baumannii acquisition is associated with severe adverse outcomes, including increased mortality, need for mechanical ventilation, and reduced functional status.