AUTHOR=Ma Jiangang  , Wang Juan , Feng Jie , Liu Yingqiu , Yang Baowei , Li Ruichao , Bai Li , He Tao , Wang Xinglong , Yang Zengqi 

TITLE=Characterization of Three Porcine Acinetobacter towneri Strains Co-Harboring tet(X3) and blaOXA-58

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=10

YEAR=2020

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2020.586507

DOI=10.3389/fcimb.2020.586507

ISSN=2235-2988

ABSTRACT=<p>Tigecycline is the antibiotic of last resort for the treatment of extensively drug-resistant bacterial infections, mainly those of multidrug-resistant Gram-negative bacteria. The plasmid-mediated <italic>tet</italic>(X3) gene has recently been described in various pathogens that are resistant to tigecycline. We report three tigecycline-resistant <italic>Acinetobacter towneri</italic> strains isolated from porcine faeces in China, which all contained the <italic>tet</italic>(X3)-harboring plasmids. A broth microdilution method was used to examine the antimicrobial susceptibility of the isolates, and S1-Nuclease digestion pulsed-field gel electrophoresis (S1-PFGE) was used to characterize their plasmid profiles. The whole-genome sequences of the isolates were determined with the Nanopore PromethION platform. The sequence analysis indicated that the strains were <italic>A. towneri.</italic> They showed resistance to multiple antibiotics, and all the resistance genes were located on plasmids. The three <italic>tet</italic>(X3)-harboring plasmids had a similar backbone structure, and all contained <italic>bla</italic><sub>OXA-58</sub> with various insertion elements (IS). IS<italic>CR2</italic> is considered an important factor in <italic>tet</italic>(X3) mobilization. In addition to IS<italic>CR2</italic>, we demonstrate that IS<italic>26</italic> generates a circular intermediate containing the <italic>tet</italic>(X3) gene, which could increase the dissemination risk. To our knowledge, this is the first report of <italic>tet</italic>(X3)- and <italic>bla</italic><sub>OXA-58</sub>-harboring plasmids in <italic>A. towneri</italic>. Because the IS<italic>26</italic> is frequently found in front of <italic>tet</italic>(X3), research should be directed toward the action of IS<italic>26</italic> in the spread of <italic>tet</italic>(X3).</p>