Characterization of a genomic Island carrying the tet(X4) gene in porcine Acinetobacter towneri co-harboring plasmid-borne blaNDM−1 and blaOXA−58 genes

Abstract

Tigecycline and carbapenems are last-resort antimicrobial agents to treat serious infections caused by multi-drug resistant bacterial pathogens. However, the co-occurrence of tigecycline and carbapenem resistance determinants challenges the clinical efficacy of these antimicrobial agents. In this study, we report the co-existence of tet(X4), blaNDM−1 and blaOXA−58 genes in the porcine Acinetobacter towneri isolate 19110F47. Sequence analysis revealed that tet(X4) gene, along with the florfenicol resistance gene floR, was flanked by three copies of IS91-like elements, which can form three different translocatable units (TUs), and were located in a 41,098-bp multidrug resistance region (MDRR) within a novel 100,354-bp genomic island (GI) region. TUs comprising floR-virD2-ISVsa3, hp-abh-tet(X4)-ISVsa3 and virD2-floR-ISVsa3-hp-abh-tet(X4)-ISVsa3 can be looped out from the chromosomal DNA and facilitate the transfer of the TU-based resistance genes into other plasmidic or chromosomal sites. In addition, the carbapenemase genes blaNDM−1 and blaOXA−58 were found on different non-conjugative multiresistance plasmids in this isolate, with the genetic contexts ISAba125-blaNDM−1-bleMBL-tnpR and ΔISAba3-blaOXA−58-ISAba3, respectively. The simultaneous occurrence of tet(X4), blaNDM−1 and blaOXA−58 in the same porcine A. towneri isolate emphasizes the importance of antimicrobial resistance surveillance in food-producing animals.

Decoding the enigma: unveiling the molecular transmission of avian-associated tet(X4)-positive E. coli in Sichuan Province, China

“…The reason for this repeat unit formation appears to be related to IS Vsa3 , a member of the IS 91 family, that unlike other insertion families that require 2 copies of the IS element, the IS 91 family requires only 1 copy to mobilize ARGs transfer ( Toleman et al, 2006 ). In addition, IS Vsa3 mediates the formation of a transposable unit by tet (X4) ( Li et al, 2022 ). This circular transposable unit in turn recognizes the IS site and then inserts to generate a new copy, resulting in a tandem duplication of the tet (X4) gene ( Li et al, 2021 ).…”

Molecular mechanisms of tigecycline-resistance among Enterobacterales

“…Antibiotic resistance genes (ARGs) are recognized as novel hazards, which could be disseminated worldwide simply via various reservoirs such as soil, water, and animal excrement. Certain ARGs can also be a part of a multidrug-resistance region located on a genomic island presented in chromosomal DNA ( Li et al., 2022 ). Moreover, a phenomenon of the coexistence of several resistant genes was reported and previously described in Enterobacterales ( Wang Q. et al., 2022 ).…”