Endemicity and diversification of carbapenem-resistant Acinetobacter baumannii in an intensive care unit

Emma L Doughty; Haiyang Liu; Robert A Moran; Xiaoting Hua; Xiaoliang Ba; Feng Guo; Xiangping Chen; Linghong Zhang; Mark Holmes; Willem van Schaik; Alan McNally; Yunsong Yu

doi:10.1016/j.lanwpc.2023.100780

Endemicity and diversification of carbapenem-resistant Acinetobacter baumannii in an intensive care unit

Lancet Reg Health West Pac. 2023 May 9:37:100780. doi: 10.1016/j.lanwpc.2023.100780. eCollection 2023 Aug.

Authors

Affiliations

¹ Institute of Microbiology and Infection, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK.
² Department of Infectious Diseases, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310016, China.
³ Department of Veterinary Medicine, University of Cambridge, Cambridge, UK.

Abstract

Background: Carbapenem-resistant Acinetobacter baumannii (CRAB) is a major public health concern globally. Often studied in the context of hospital outbreaks, little is known about the persistence and evolutionary dynamics of endemic CRAB populations.

Methods: A three-month cross-sectional observational study was conducted in a 28-bed intensive care unit (ICU) in Hangzhou, China. A total of 5068 samples were collected from the hospital environment (n = 3985), patients (n = 964) and staff (n = 119). CRAB isolates were obtained from 10.5% of these samples (n = 532). All of these isolates, plus an additional 19 from clinical infections, were characterised through whole-genome sequencing.

Findings: The ICU CRAB population was dominated by OXA-23-producing global clone 2 isolates (99.3% of all isolates) that could be divided into 20 distinct clusters, defined through genome sequencing. CRAB was persistently present in the ICU, driven by regular introductions of distinct clusters. The hospital environment was heavily contaminated, with CRAB isolated from bed units on 183/335 (54.6%) sampling occasions but from patients on only 72/299 (24.1%) occasions. CRAB was spread to adjacent bed units and rooms, and following re-location of patients within the ICU. We also observed three horizontal gene transfer events between CRAB strains in the ICU, involving three different plasmids.

Interpretation: The epidemiology of CRAB in this setting contrasted with previously described clonal outbreaks in high-income countries, highlighting the importance of environmental CRAB reservoirs in ICU epidemiology and the unique challenges in containing the spread of CRAB in ICUs where this important multidrug-resistant pathogen is endemic.

Funding: This work was undertaken as part of the DETECTIVE research project funded by the Medical Research Council (MR/S013660/1), National Natural Science Foundation of China (81861138054, 32011530116, 31970128, 31770142), Zhejiang Province Medical Platform Backbone Talent Plan (2020RC075), and the National Key Research and Development Program of China grant (2018YFE0102100). W.v.S was also supported by a Wolfson Research Merit Award (WM160092).

Keywords: Antimicrobial resistance; Carbapenem-resistant Acinetobacter baumannii; Genomic epidemiology; Horizontal gene transfer; Infection prevention and control; Intensive care.

Grants and funding

MR/S013660/1/MRC_/Medical Research Council/United Kingdom