Emergence and Evolution of OXA-23-Producing ST46Pas-ST462Oxf-KL28-OCL1 Carbapenem-Resistant Acinetobacter baumannii Mediated by a Novel IS Aba1-Based Tn 7534 Transposon

Haiyang Liu; Xiaochen Liu; Jintao He; Linghong Zhang; Feng Zhao; Zhihui Zhou; Xiaoting Hua; Yunsong Yu

doi:10.3390/antibiotics12020396

Emergence and Evolution of OXA-23-Producing ST46_Pas-ST462_Oxf-KL28-OCL1 Carbapenem-Resistant Acinetobacter baumannii Mediated by a Novel IS Aba1-Based Tn 7534 Transposon

Antibiotics (Basel). 2023 Feb 16;12(2):396. doi: 10.3390/antibiotics12020396.

Authors

Haiyang Liu^{1

2

3}, Xiaochen Liu^{1

2

3}, Jintao He^{1

2

3}, Linghong Zhang^{1

2

3}, Feng Zhao^{4

5}, Zhihui Zhou^{1

2

3}, Xiaoting Hua^{1

2

3}, Yunsong Yu^{1

2

3}

Affiliations

¹ Department of Infectious Diseases, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310016, China.
² Key Laboratory of Microbial Technology and Bioinformatics of Zhejiang Province, Hangzhou 310016, China.
³ Regional Medical Center for National Institute of Respiratory Diseases, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310016, China.
⁴ Department of Clinical Laboratory, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310016, China.
⁵ Key Laboratory of Precision Medicine in Diagnosis and Monitoring Research of Zhejiang Province, Hangzhou 310016, China.

Abstract

Carbapenem-resistant Acinetobacter baumannii (CRAB) isolates of global clone 1 (GC1) and global clone 2 (GC2) have been widely reported. Nevertheless, non-GC1 and non-GC2 CRAB strains have been studied less. In particular, no reports concerning sequence type 46 (ST46_Pas) CRAB strains have been described thus far. In this work, the genomic features and possible evolution mechanism of ST46_Pas OXA-23-producing CRAB isolates from clinical specimens are reported for the first time. Antimicrobial susceptibility testing of three ST46_Pas strains revealed identical resistance profiles (resistance to imipenem, meropenem, ciprofloxacin and the combination of cefoperazone/sulbactam at a 2:1 ratio). They were found to belong to ST46_Pas and ST462_Oxf with capsular polysaccharide 28 (KL28) and lipooligosaccharide 1 (OCL1), respectively. Whole-genome sequencing (WGS) revealed that all contained one copy of chromosomal bla_OXA-23, which was located in a novel ISAba1-based Tn7534 composite transposon. In particular, another copy of the Tn7534 composite transposon was identified in an Hgz_103-type plasmid with 9 bp target site duplications (TSDs, ACAACATGC) in the A. baumannii ZHOU strain. As the strains originated from two neighboring intensive care units (ICUs), ST46_Pas OXA-23-producing CRAB strains may have evolved via transposition events or a pdif module. Based on the GenBank database, ST46_Pas strains were collected from various sources; however, most were collected in Hangzhou (China) from 2014 to 2021. Pan-genome analysis revealed 3276 core genes, 0 soft-core genes, 768 shell genes and 443 cloud genes shared among all ST46_Pas strains. In conclusion, the emergence of ST46_Pas CRAB strains might present a new threat to healthcare settings; therefore, effective surveillance is required to prevent further dissemination.

Keywords: CRAB; OXA-23; ST46Pas; Tn7534; evolution; novel transposon.

Abstract

Grants and funding