Epidemiology of Bloodstream Infections Caused by Acinetobacter baumannii and Impact of Drug Resistance to both Carbapenems and Ampicillin-Sulbactam on Clinical Outcomes

Abstract

ABSTRACTAcinetobacter baumanniihas become a leading cause of bloodstream infections (BSI) in health care settings. Although the incidence of infection with carbapenem- and ampicillin-sulbactam-resistant (CASR)A. baumanniihas increased, there is a scarcity of studies which investigate BSI caused by CASRA. baumannii. A retrospective cohort study was conducted on adult patients with BSI caused byA. baumanniiand who were admitted to the Detroit Medical Center between January 2006 and April 2009. Medical records were queried for patients' demographics, antimicrobial exposures, comorbidities, hospital stay, and clinical outcomes. Bivariate analyses and logistic regression were employed in the study. Two hundred seventy-four patients with BSI caused byA. baumanniiwere included in the study: 68 (25%) caused by CASRA. baumanniiand 206 (75%) caused by non-CASRA. baumannii. In multivariate analysis, factors associated with BSI caused by CASRA. baumanniiincluded admission with a rapidly fatal condition (odds ratio [OR] = 2.83, 95% confidence interval [CI] = 1.27 to 6.32,Pvalue = 0.01) and prior use of antimicrobials (OR = 2.83, 95% CI = 1.18 to 6.78,Pvalue = 0.02). In-hospital mortality rates for BSI caused by CASRA. baumanniiwere significantly higher than those for non-CASRA. baumannii-induced BSI (43% versus 20%; OR = 3.0, 95% CI = 1.60 to 5.23,Pvalue < 0.001). However, after adjusting for potential confounders, the association between BSI caused by CASRA. baumanniiand increased risk of in-hospital mortality was not significant (OR = 1.15, 95% CI = 0.51 to 2.63,Pvalue = 0.74). This study demonstrated that CASRA. baumanniihad a distinct epidemiology compared to more susceptibleA. baumanniistrains; however, clinical outcomes were similar for the two groups. Admission with a rapidly fatal condition was an independent predictor for both CASRA. baumanniiand in-hospital mortality.