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Critical Care Medicine:
doi: 10.1097/CCM.0000000000000125
Clinical Investigations

Risk Factors and Outcome Analysis of Acinetobacter baumannii Complex Bacteremia in Critical Patients*

Lee, Hao-Yuan MD1,2,3; Chen, Chyi-Liang PhD2,3; Wu, Si-Ru BS3; Huang, Chih-Wei BS3; Chiu, Cheng-Hsun MD, PhD1,2,3

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Abstract

Objectives: Acinetobacter baumannii complex bacteremia has been identified increasingly in critical patients admitted in ICUs. Notably, A. baumannii complex bacteremia has a high mortality rate, yet the risk factors associated with mortality remain unclear and controversial.

Design: Retrospective study.

Setting: All adult ICUs at a tertiary care medical center.

Patients: All patients with A. baumannii complex bacteremia admitted in 2009–2010.

Interventions: None.

Measurements and Main Results: Risk factors for mortality were analyzed. Bacterial isolates were identified by 16S-23S ribosomal RNA intergenic spacer region sequencing for genospecies and genotyped by pulsed-field gel electrophoresis. Carbapenemase genes were detected by polymerase chain reaction and sequencing. A total of 298 patients met the inclusion criteria, including 73 (24.5%) infected by imipenem-resistant A. baumannii complex. The overall 30-day mortality was 33.6% (100 of 298). Imipenem-resistant A. baumannii complex bacteremia specifically showed a high mortality (69.9%) and was associated with prior use of broad-spectrum antibiotics for more than 5 days for treating ventilator-associated pneumonia before the occurrence of bacteremia. Mortality was associated with inappropriate initial antimicrobial therapy, which was correlated with imipenem-resistant A. baumannii complex but not with any specific genospecies. ISAba1blaOXA-23–ISAba1 (Tn2006) was found in most (66.7%, 40 of 68) imipenem-resistant A. baumannii (genospecies 2) and also spread beyond species border to all imipenem-resistant genospecies 3 (2), 13TU (2), and 10 (1).

Conclusions: For critical patients with A. baumannii complex infection, ventilator-associated pneumonia in particular, the selective pressure from prior use of broad-spectrum antibiotics for 5 days or more increased risk of subsequent imipenem-resistant A. baumannii complex bacteremia. To reduce mortality, rapid identification of imipenem-resistant A. baumannii complex and early initiation of appropriate antimicrobial therapy in these high-risk patients are crucial.

© 2014 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins

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