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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

doi: 10.1097/CCM.0000000000000125
Clinical Investigations

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.

1Graduate Institute of Clinical Medical Sciences, Chang Gung University College of Medicine, Taoyuan, Taiwan.

2Department of Pediatrics, Chang Gung Children’s Hospital, Chang Gung University College of Medicine, Taoyuan, Taiwan.

3Molecular Infectious Disease Research Center, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taoyuan, Taiwan.

* See also p. 1289.

Dr. Lee designed the study, collected and analyzed the data, and wrote the article. Dr. Chen analyzed the data. Ms. Wu and Mr. Huang performed the experiments. Dr. Chiu designed the study, collected and analyzed the data, and wrote the article. All authors read and approved the final article.

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Supported, in part, by grants 100-2314-B-182A-049 and 102-2314-B-182A-023 from National Science Council, Executive Yuan, Taiwan, and by grants CMRPG490052 and CMRPG4C0031 from Chang Gung Memorial Hospital, Taiwan.

Dr. Lee, Dr. Chen, Ms. Wu, Mr. Huang, and Dr. Chiu’s institutions received grant support from National Science Council and Chang Gung Memorial Hospital (Taipei, Taiwan). Dr. Lee, Dr. Chen, Ms. Wu, Mr. Huang, and Dr. Chiu received support for article research from National Science Council and Chang Gung Memorial Hospital.

For information regarding this article, E-mail: chchiu@adm.cgmh.org.tw

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