Emergence in Taiwan of novel imipenem-resistant Acinetobacter baumannii ST455 causing bloodstream infection in critical patients

Hao-Yuan Lee; Chih-Wei Huang; Chyi-Liang Chen; Yi-Hsin Wang; Chee-Jen Chang; Cheng-Hsun Chiu

doi:10.1016/j.jmii.2015.04.001

Emergence in Taiwan of novel imipenem-resistant Acinetobacter baumannii ST455 causing bloodstream infection in critical patients

J Microbiol Immunol Infect. 2015 May 13:S1684-1182(15)00728-8. doi: 10.1016/j.jmii.2015.04.001. Online ahead of print.

Authors

Hao-Yuan Lee¹, Chih-Wei Huang², Chyi-Liang Chen², Yi-Hsin Wang², Chee-Jen Chang³, Cheng-Hsun Chiu⁴

Affiliations

¹ Graduate Institute of Clinical Medical Sciences, Chang Gung University College of Medicine, Taoyuan, Taiwan; Department of Pediatrics, Chang Gung Children's Hospital, Chang Gung University College of Medicine, Taoyuan, Taiwan; Molecular Infectious Disease Research Center, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taoyuan, Taiwan.
² Molecular Infectious Disease Research Center, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taoyuan, Taiwan.
³ Graduate Institute of Clinical Medical Sciences, Chang Gung University College of Medicine, Taoyuan, Taiwan.
⁴ Graduate Institute of Clinical Medical Sciences, Chang Gung University College of Medicine, Taoyuan, Taiwan; Department of Pediatrics, Chang Gung Children's Hospital, Chang Gung University College of Medicine, Taoyuan, Taiwan; Molecular Infectious Disease Research Center, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taoyuan, Taiwan. Electronic address: chchiu@adm.cgmh.org.tw.

PMID: 26055691
DOI: 10.1016/j.jmii.2015.04.001

Abstract

Background: Acinetobacter baumannii is one of the most important noscomial pathogens worldwide. The study aimed to use multilocus sequence typing (MLST) for epidemiological surveillance of A. baumannii isolates in Taiwan and analyze the clinical presentations and patients' outcomes.

Methods: MLST according to both Bartual's PubMLST and Pasteur's MLST schemes was applied to characterize bloodstream imipenem-resistant A. baumannii (IRAB) infection in intensive care units in a medical center. A total of 39 clinical IRAB bloodstream isolates in 2010 were enrolled. We also collected 13 imipenem-susceptible A. baumannii bloodstream isolates and 30 clinical sputum isolates (24 IRAB and 6 imipenem-susceptible A. baumannii) for comparison. Clinical presentations and outcome of the patients were analyzed.

Results: We found that infection by ST455^B/ST2^P and inappropriate initial therapy were statistically significant risk factors for mortality. More than one third of the IRAB isolates belonged to ST455^B/ST2^P. Most ST455^B/ST2^P (80%) carried ISAba1-bla_OXA-23, including 10 (66.7%) with Tn2006 (ISAba1-bla_OXA-23-ISAba1) in an AbaR4-type resistance island. ST455^B/ST2^P appears to evolve from ST208^B/ST2^P of clonal complex (CC) 92^B/CC2^P. In this hospital-based study, A. baumannii ST455 accounted for 38.5% of IRAB bacteremia, with a high mortality of 86.7%. Approximately 85% of ST455^B/ST2^P bacteremia had a primary source of ventilation-associated pneumonia.

Conclusion: We report the emergence in Taiwan of IRAB ST455^B/ST2^P, which is the current predominant clone of IRAB in our hospital and has been causing bacteremia with high mortality in critical patients.

Keywords: Acinetobacter baumannii; bacteremia; imipenem resistance; mortality; sequence type.