Influence of ACB complex genospecies on clinical outcomes in a U.S. hospital with high rates of multidrug resistance

Objectives: Bacteria within the Acinetobacter calcoaceticus-Acinetobacter baumannii (ACB) complex commonly cause nosocomial infection and are often multidrug resistant. Advances in genospecies typing allow for speciation within the ACB complex; however, little is known about the effect of genospecies on patient outcomes. Methods: Adult patients with ACB complex bacteremia from Jan 2005-Oct 2012 were included. Bacterial isolates were speciated by rpoB gene sequence analysis, and clinical data were collected. Results: Of 147 patients with ACB complex bacteremia, 116 had A. baumannii (78.9%), 28 had Acinetobacter pittii (19.0%), and 3 had Acinetobacter nosocomialis (2.0%). A. baumannii bacteremia was associated with greater comorbidity and was more frequently multidrug resistant (79% vs. 16%, p<0.01). Multidrug resistant A. baumannii but not susceptible A. baumannii was associated with worse outcomes compared to non-. baumannii ACB complex bacteremia. Neither multidrug resistance nor genospecies was an independent predictor of mortality, but receipt of appropriate therapy was associated with decreased risk of mortality (OR, 0.13; 95% CI, 0.04-0.44; p<0.01). Conclusions: A. baumannii bacteremia is associated with worse clinical outcomes than non-. baumannii ACB complex bacteremia. The difference, however, appears to be related to multidrug resistance and attendant receipt of appropriate therapy rather than genospecies.