Whole-genome analysis of New Delhi Metallo-Beta-Lactamase-1-producing Acinetobacter haemolyticus from China

Abstract

Objective: Infections caused by multidrug-resistant Acinetobacter spp. have generated worldwide attention. With the increasing isolation of non-baumannii Acinetobacter, the nature of associated infection and resistance needs to be explored. This study aimed to analyse the characteristics of New Delhi Metallo-Beta-Lactamase-1 (NDM-1)-producing Acinetobacter haemolyticus (named sz1652) isolated from Shenzhen city, China. Methods: The antibiotic spectrum was analysed after antimicrobial susceptibility testing. Combined disk test (CDT) was used to detect the metallo-beta-lactamases (MBLs). Transferability of carbapenem resistance was tested by filter mating experiments and plasmid transformation assays. Whole-genome sequencing (WGS) was performed using HiSeq 2000 and PacBio RS system. Results: The Acinetobacter haemolyticus strain sz1652 was resistant to carbapenems and other tested agents except for amikacin, tigecycline and colistin. Production of MBLs was confirmed by CDT. Transfer of carbapenem resistance was unsuccessful. WGS analysis showed that the genome of sz1652 comprised a chromosome and two plasmids; 16 genomic islands (GIs) were predicted. Genes associated with resistance were found in this strain, including the beta-lactamase genes blaNDM-1, blaOXA-214 and blaLRA-18, the fluoroquinolone resistant-related mutations [GyrA subunits (Ser81Ile) and ParC subunits (Ser84Tyr)], and efflux pump genes related to tetracycline and macrolide resistance. Analysis of the genetic environment showed that blaNDM-1 was embedded in Tn125 transposon. The Tn125 structure was chromosomally located and shared > 99% sequence identity with the previously reported blaNDM-1 carrying region. Conclusion: The NDM-1-producing Acinetobacter haemolyticus coexisted with multiple drug-resistant determinants. The acquisition of the blaNDM-1 gene was probably facilitated by Tn125 in this strain. Non-Acinetobacter baumannii species also contained GIs.

Keywords

• Acinetobacter haemolyticus
• Carbapenemase
• Resistome
• blaNDM-1
• Genomic islands