Acinetobacter baumannii and Acinetobacter genospecies 13TU and 3 bacteraemia: comparison of clinical features, prognostic factors and outcomes

Abstract

Objectives: To investigate the clinical impact of different genospecies of the Acinetobacter calcoaceticus-Acinetobacter baumannii complex (ACB complex; A. baumannii, Acinetobacter gen. sp. 13TU and Acinetobacter gen. sp. 3) on the severity of bacteraemia.

Methods: We retrospectively compared the clinical features and outcomes of patients with bacteraemia caused by A. baumannii, Acinetobacter gen. sp. 13TU or Acinetobacter gen. sp. 3. The genospecies were identified using oligonucleotide array sequence analysis (interspacer sequence), and the clonality of Acinetobacter gen. sp. 13TU and 3 isolates was determined by PFGE analysis.

Results: A total of 215 patients with bacteraemia due to ACB complex were evaluated. Among them, 117 (54.4%) had A. baumannii bacteraemia, 77 (35.8%) had Acinetobacter gen. sp. 13TU bacteraemia and 21 (9.8%) had Acinetobacter gen. sp. 3 bacteraemia. A. baumannii bacteraemia was associated with a higher 14 day mortality rate (P < 0.001), a higher 30 day mortality rate (P < 0.001) and a higher in-hospital mortality rate than bacteraemia due to Acinetobacter gen. sp. 13TU or Acinetobacter gen. sp. 3. Independent prognostic factors for the 30 day mortality included the Charlson co-morbidity index (P < 0.001) and Pitt bacteraemia score (P < 0.001). Bloodstream infection caused by a multidrug-resistant A. baumannii isolate appeared to be associated with a poor outcome (P = 0.069). There was no clonal spread of Acinetobacter gen. sp. 13TU or Acinetobacter gen. sp. 3 during the study period.

Conclusions: Bacteraemia due to multidrug-resistant strains but not A. baumannii per se appears to be associated with poor outcome.