■替加环素耐药肠杆菌已成为公众关注的焦点,和移动tet(X)变体和tmexCD-toprJ外排泵主要负责替加环素耐药性的传播。医院污水被认为是抗生素耐药性的重要蓄水池,而在这一生态位中对替加环素的耐药性研究不足。
■在这项研究中,从一组替加环素耐药肠杆菌中筛选出5株大肠埃希菌和6株肺炎克雷伯菌,通过药敏试验进行进一步调查,共轭,全基因组测序,和生物信息学分析。
■所有五种大肠杆菌菌株都带有tet(X4),它位于不同的质粒上,包括新型的IncC/IncFIA(HI1)/IncHI1A/IncHI1B(R27)杂化构造。此外,携带tet(X4)的质粒能够通过缀合转移并在不存在抗生素的情况下在受体中稳定。tmexCD1-toprJ1在两种肺炎克雷伯菌(LZSFT39和LZSRT3)中被鉴定,它由一种新型的多药耐药转座子携带,在新的IncR/IncU杂交质粒上命名为Tn7368。此外,我们发现两种肺炎克雷伯菌(LZSFZT3和LZSRT3)表现出过表达外排基因acrB和oqxB,分别,这很可能是由ramR和oqxR的突变引起的。
■总而言之,这项研究的发现扩大了我们对携带替加环素抗性基因的遗传元件的认识,建立了研究人类结构多样性和进化轨迹的基线,动物,和环境替加环素抗性体。
UNASSIGNED: The tigecycline-resistant Enterobacterales have emerged as a great public concern, and the mobile tet(X) variants and tmexCD-toprJ 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.
UNASSIGNED: In this study, five Escherichia coli and six Klebsiella pneumoniae strains were selected from a collection of tigecycline-resistant Enterobacterales for further investigation by antimicrobial susceptibility testing, conjugation, whole-genome sequencing, and bioinformatics analysis.
UNASSIGNED: All five E. coli strains harbored tet(X4), which was located on different plasmids, including a novel IncC/IncFIA(HI1)/IncHI1A/IncHI1B(R27) hybrid structure. In addition, tet(X4)-bearing plasmids were able to transfer by conjugation and be stabilized in the recipient in the absence of antibiotics. tmexCD1-toprJ1 was identified in two K. pneumoniae (LZSFT39 and LZSRT3) and it was carried by a novel multidrug-resistance transposon, designated Tn7368, on a novel IncR/IncU hybrid plasmid. In addition, we found that two K. pneumoniae (LZSFZT3 and LZSRT3) showed overexpression of efflux genes acrB and oqxB, respectively, which was most likely to be caused by mutations in ramR and oqxR.
UNASSIGNED: 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.