Clinical impact of pneumonia caused by Acinetobacter baumannii in intubated patients: A matched cohort study*

Abstract

To determine whether ventilator-associated pneumonia caused by Acinetobacter baumannii (VAPAB) is associated with increased mortality rate. A retrospective matched case-control study in which all intensive care unit adult patients with microbiologically documented VAPAB were defined as cases. Four intensive care units from teaching hospitals. Sixty patients were matched to sixty controls. Controls were matched based on stay before pneumonia onset, disease severity (Acute Physiology and Chronic Health Evaluation II) at admission, and diagnostic category. Population characteristics and intensive care unit mortality rates of patients with VAPAB and their controls were compared. Attributable mortality was determined by subtracting the crude mortality rate of the controls from the crude mortality rate of the case patients. Twenty-four of the 60 case patients died, representing a crude mortality rate of 40%, whereas 17 of the 60 controls died, a crude mortality rate of 28.3% (p =.17). Crude intensive care unit mortality was the same (12 of 35, 34.2%) in patients with VAPAB caused by strains sensitive to imipenem and in their matched controls. It was 44% for the 25 patients with imipenem-resistant strains with an estimated attributable mortality rate of 20.0% (95% confidence interval, -5.6% to 45.7%). Mean intensive care unit stay of patients and controls was 35.3 and 36.6 days, respectively (p = nonsignificant). In intubated patients, pneumonia by A. baumannii is not significantly associated with attributable mortality rate or an increased length of intensive care unit stay.