Abstract
The purpose of this study was to characterize the complete sequence of a novel plasmid carrying tigecycline resistance gene tet(X) and carbapenemase gene blaOXA-58 from a swine Acinetobacter sp. strain SH19PTT10. Minimal inhibitory concentration (MIC) was performed using microbroth dilution method. The isolate SH19PTT10 was highly resistant (16 mg/L) to tigecycline, and also exhibited resistance to ampicillin, streptomycin, tetracycline, chloramphenicol, florfenicol, ciprofloxacin, and sulfamethoxazole/trimethoprim. Although SH19PTT10 harbored blaOXA-58, it was susceptible to cefotaxime and meropenem. The genome sequence of SH19PTT10 was determined using PacBio single-molecule real-time sequencing. Plasmid pYUSHP10-1 had a size of 174,032 bp and showed partial homology to several plasmids found in Acinetobacter isolates. It contained two repA genes, putative toxin-antitoxin systems (HipA/HipB, RelE/RelB, and BrnT/BrnA), partitioning genes (parA and parB), and heavy metal resistance-associated genes (copA/copB, nrp, and czcA/czcD) but the transfer region or proteins was not found. pYUSHP10-1 carried 16 resistance genes, mainly clustered in two mosaic multiresistance regions (MRRs). The first MRR contained sul3, qacI-aadA1-clmA1-aadA2-blaCARB-2-dfrA16 cassette, aac(3)-IId, and blaOXA-58. The blaOXA-58 gene was associated with ISAba3, as previously described. The second MRR is the tet(X) region (ISAcsp12-aph(3')-Ia-IS26-ΔxerD-tet(X)-res-ISCR2-sul2) related to the corresponding region in other tet(X)-bearing plasmids. The pdif sites, as well as mobile elements, play an important role in mobilization of DNA modules and plasmid evolution. Coexistence of numerous resistance genes on a single plasmid may contribute to the dissemination of these genes under pressure posed by different agents, which may explain the presence of clinically crucial resistance genes tet(X) and blaOXA-58 in livestock. Thus, rational drug use and continued surveillance of tet(X) and blaOXA-58 in livestock are warranted.
Highlights
The genus Acinetobacter currently includes more than 60 species with valid species names1, and most of them are important nosocomial pathogens
The isolate SH19PTT10 was tested for minimal inhibitory concentrations (MICs) of ampicillin, cefotaxime, meropenem, amikacin, streptomycin, tetracycline, minocycline, tigecycline, chloramphenicol, florfenicol, ciprofloxacin, colistin, and sulfamethoxazole/trimethoprim using microbroth dilution method recommended by the guidelines of the Clinical and Laboratory Standards Institute [CLSI, Wayne, PA, United States; Clinical and Laboratory Standards Institute (CLSI), 2012]
The 16S ribosomal RNA (rRNA) gene sequencing showed SH19PTT10 belonging to Acinetobacter but not to any described species, whole genome sequencing (WGS) was further performed
Summary
The genus Acinetobacter currently includes more than 60 species with valid species names, and most of them are important nosocomial pathogens. OXA-58 has been detected in Acinetobacter isolates from patients, animals, and the environment from distinct geographical areas, in clinics (Poirel et al, 2005; Fu et al, 2014; Feng et al, 2016; Klotz et al, 2017; Narciso et al, 2017; Chen et al, 2019; Matos et al, 2019; Suzuki et al, 2019). Novel plasmid-mediated high-level tigecycline resistance genes tet(X) [former name tet(X3)~tet(X5)]2 have been identified in Acinetobacter isolates from animals and humans in China in 2019 (He et al, 2019; Wang et al, 2019). MK134375] and blaOXA-58 obtained from a swine Acinetobacter sp. strain in Shanghai, China, providing insights into the genetic structures of the plasmid and these genes
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