Clinical Outcomes of Hospital-Acquired Infection with Acinetobacter nosocomialis and Acinetobacter pittii

Abstract

ABSTRACTThe role ofAcinetobacter nosocomialisandAcinetobacter pittii, which belong to theA. calcoaceticus-A. baumanniicomplex, in hospital-acquired infections is increasingly recognized. Here we describe a retrospective cohort study of hospital-acquiredA. calcoaceticus-A. baumanniicomplex infections at a university hospital in Thailand. A total of 222 unique cases were identified between January 2010 and December 2011. The genomospecies of theA. calcoaceticus-A. baumanniicomplex isolates were classified as follows:A. baumannii, 197 (89%);A. nosocomialis, 18 (8%); andA. pittii, 7 (3%). AllA. nosocomialisandA. pittiiisolates were susceptible to imipenem and meropenem. The patients infected withA. nosocomialisandA. pittiihad lower 30-day mortality than those infected with carbapenem-susceptibleA. baumannii(P= 0.025) and carbapenem-resistantA. baumannii(P= 0.013). The factors influencing 30-day mortality were infection with non-baumannii A. calcoaceticus-A. baumanniicomplex (hazard ratio [HR], 0.12; 95% confidence interval [CI], 0.03 to 0.51;P= 0.004), infection with carbapenem-resistantA. baumannii(HR, 1.57; 95% CI, 0.89 to 2.79;P= 0.105), appropriate empirical antimicrobial therapy (HR, 0.38; 95% CI, 0.23 to 0.61;P< 0.001), and higher acute physiology and chronic health evaluation II (APACHE II) score (HR, 1.15; 95% CI, 1.10 to 1.19;P< 0.001). InGalleria mellonellaassays, the survival rates were significantly higher for the larvae infected withA. nosocomialisorA. pittiithan for those infected with either carbapenem-susceptibleA. baumanniior carbapenem-resistantA. baumannii, but no differences in survival rates were observed between carbapenem-susceptibleA. baumanniiand carbapenem-resistantA. baumannii. These findings suggest intrinsic differences in virulence between non-baumannii A. calcoaceticus-A. baumanniicomplex species andA. baumanniibut not between carbapenem-susceptible and resistantA. baumannii.