Prophylactic antibiotic days as a predictor of sensitivity patterns in Acinetobacter pneumonia.

Background: Ventilator-associated pneumonia (VAP) secondary to Acinetobacter spp. in critically ill trauma patients has increased. More importantly, the incidence of multi-drug-resistant (MDR) Acinetobacter VAP has increased. The risk factors for this increase in resistance have yet to be elucidated. The purpose of this study was to evaluate the change in Acinetobacter sensitivity over time and determine which risk factors predict resistance in trauma patients.

Methods: Patients surviving >5 days post-injury who had Acinetobacter VAP (≥10(5) colony-forming units/mL in bronchoalveolar lavage fluid) who were seen over five years were divided according to pathogen sensitivity (sensitive [SEN] vs. MDR) and stratified by age, severity of shock (base excess, number of blood transfusions), injury severity (Injury Severity Score [ISS], admission Glasgow Coma Scale [GCS] score, chest and extremity Abbreviated Injury Scale score [AIS]), and year. Prophylactic (Pro), empiric (Emp), Pro + Emp, and total antibiotic days, ventilator days, and mortality rate were compared. Multivariable logistic regression (MLR) was performed to determine which risk factors were independent predictors of resistance.

Results: Ninety-six patients (81% male) were identified: 62 SEN and 34 MDR. The groups were clinically similar in terms of age, extent of shock, and injury severity with the exception of extremity AIS. Antibiotic exposure was greater in the MDR group. Over the period of the study, the incidence of MDR Acinetobacter VAP increased from zero to 66% (p < 0.0001). Multiple logistic regression identified Pro antibiotic days as an independent predictor of MDR after adjusting for age and chest AIS (p < 0.0001).

Conclusions: The incidence of MDR Acinetobacter VAP has increased over time. More severe extremity injuries, as measured by the AIS, may contribute to prolonged antibiotic exposure in those patients with MDR Acinetobacter VAP. Multiple logistic regression identified Pro antibiotic days as an independent risk factor for MDR Acinetobacter VAP in trauma patients.