摘要
目标
印第安纳州耐多药（MDR）肠炎沙门氏菌血清型的出现引起了全球的关注。移动遗传元件（MGE）在加速细菌群落中抗性基因的传播方面发挥着至关重要的作用。该研究旨在提高我们对潜在耐药性机制的理解，并表征耐多药印第安纳分离株中的MGE。
方法
在此，我们报道了一种耐多药致病性印第安纳S.Indiana分离株的特征。测定了S.Indiana QT6365的抗菌药敏模式。通过全基因组测序分析了染色体和质粒的基因组结构、血清型和多基因座序列类型。通过反向聚合酶链反应和测序证实了来源于IS26侧翼转座子的环状。
后果
S.Indiana QT6365对除氨曲南、阿米卡星、多粘菌素和替加环素外的所有测试的抗菌药物均表现出耐药性，被定义为MDR，属于ST17。S.Indiana QT6365与食物资源S.Indiana C629亲缘关系密切，具有相似的抗性基因图谱。多重抗性基因主要由位于染色体上的新型转座子Tn7540和IncHI2/HI2A/N质粒携带。序列分析和形成的环状中间体表明，Tn7540可能通过IS26结合的可易位单元（IS26-fosA-IS26-intI1-dfrA12-aadA2-sul1-ISCR1-blaNDM-9-IS26）的同源重组产生。
结论
据我们所知，这是首次从人类标本中分离到印第安纳州南部具有blaNDM-9和fosA3的新型染色体转座子，这可能有助于抗性基因的传播，应该引起人们的重视。
ABSTRACT
Objectives
Emergence of multidrug-resistant (MDR) Salmonella enterica serovar Indiana has raised global concern. Mobile genetic elements (MGEs) play vital roles in accelerating the dissemination of resistance genes in bacteria communities. The study aims to improve our understanding of the underlying resistance mechanisms and characterize the MGEs in a MDR S. Indiana isolate.

Methods
Here, we report the characteristics of a MDR pathogenic S. Indiana isolate. The antimicrobial susceptibility pattern of S. Indiana QT6365 was determined. The genomic structure of the chromosome and the plasmid, serotype, and multi-locus sequence type were analysed by whole genome sequencing. The circular form derived from IS26-flanked transposon was confirmed by reverse polymerase chain reaction and sequencing.

Results
S. Indiana QT6365 exhibited resistance to all tested antimicrobials except for aztreonam, amikacin, polymyxin, and tigecycline, was defined as MDR, and belonged to ST17. S. Indiana QT6365 was closely related with food resource S. Indiana C629 with similar resistance gene profiles. Multiple resistance genes are mainly carried by a novel transposon Tn7540 located on the chromosome and an IncHI2/HI2A/N plasmid. Sequence analysis and the formed circular intermediate suggested Tn7540 might be generated through homologous recombination by IS26-bounded translocatable units (IS26-fosA-IS26-intI1-dfrA12-aadA2-sul1-ISCR1-blaNDM-9-IS26).

Conclusions
To the best of our knowledge, this is the first report of the novel chromosomal transposon possessing blaNDM-9 and fosA3 in S. Indiana isolated from human specimen, which might facilitate the dissemination of resistance genes and should arouse serious awareness.

https://www.sciencedirect.com/science/article/pii/S2213716523000176