AUTHOR=Li Ying , Fu Yu , Qiu Yichuan , Liu Qian , Yin Ming , Zhang Luhua 

TITLE=Genomic characterization of tigecycline-resistant Escherichia coli and Klebsiella pneumoniae isolates from hospital sewage

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1282988

DOI=10.3389/fmicb.2023.1282988

ISSN=1664-302X

ABSTRACT=<sec><title>Introduction</title><p>The tigecycline-resistant Enterobacterales have emerged as a great public concern, and the mobile <italic>tet</italic>(X) variants and <italic>tmexCD-toprJ</italic> efflux pump are mainly responsible for the spread of tigecycline resistance. Hospital sewage is considered as an important reservoir of antimicrobial resistance, while tigecycline resistance in this niche is under-researched.</p></sec><sec><title>Methods</title><p>In this study, five <italic>Escherichia coli</italic> and six <italic>Klebsiella pneumoniae</italic> strains were selected from a collection of tigecycline-resistant Enterobacterales for further investigation by antimicrobial susceptibility testing, conjugation, whole-genome sequencing, and bioinformatics analysis.</p></sec><sec><title>Results</title><p>All five <italic>E. coli</italic> strains harbored <italic>tet</italic>(X4), which was located on different plasmids, including a novel IncC/IncFIA(HI1)/IncHI1A/IncHI1B(R27) hybrid structure. In addition, <italic>tet</italic>(X4)-bearing plasmids were able to transfer by conjugation and be stabilized in the recipient in the absence of antibiotics. <italic>tmexCD1-toprJ1</italic> was identified in two <italic>K. pneumoniae</italic> (LZSFT39 and LZSRT3) and it was carried by a novel multidrug-resistance transposon, designated Tn<italic>7368</italic>, on a novel IncR/IncU hybrid plasmid. In addition, we found that two <italic>K. pneumoniae</italic> (LZSFZT3 and LZSRT3) showed overexpression of efflux genes <italic>acrB</italic> and <italic>oqxB</italic>, respectively, which was most likely to be caused by mutations in <italic>ramR</italic> and <italic>oqxR</italic>.</p></sec><sec><title>Discussion</title><p>In conclusion, the findings in this study expand our knowledge of the genetic elements that carry tigecycline resistance genes, which establishes a baseline for investigating the structure diversity and evolutionary trajectories of human, animal, and environmental tigecycline resistomes.</p></sec>