Genetic Factors Associated with Enhanced blaKPC Expression in Tn3/Tn4401 Chimeras
Genetic Factors Associated with Enhanced blaKPC Expression in Tn3/Tn4401 Chimeras
复制标题
与 Tn3/Tn4401 嵌合体中 blaKPC 表达增强相关的遗传因素
DOI：
10.1128/aac.01836-19
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发表时间：
2020-03-01
影响因子：
4.9
通讯作者：
Zhao, Zhigang
中科院分区：
文献类型：
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作者：
Huang, Jiansheng;Hu, Xiaolei;Zhao, Zhigang
blaKPC基因的表达在肠杆菌科对碳青霉烯类抗生素耐药中起着关键作用。然而，blaKPC基因的遗传调控因子尚未完全阐明，特别是Tn 3-Tn 4401嵌合体中的基因。摘要blaKPC基因的表达在肠杆菌科细菌对碳青霉烯类抗生素耐药中起着关键作用。然而，blaKPC基因的遗传调控因子尚未完全阐明，特别是Tn 3-Tn 4401嵌合体中的基因。在我院发现了两种新的Tn 3-Tn 4401嵌合体亚型，亚型A（CTA），其携带含有PX启动子的121-bp缺失，存在于22.6%（54/239）的分离株中;亚型C（CTC），其携带624-bp插入和P1启动子缺失，仅存在于1个分离株中。两种亚型的碳青霉烯MIC均为野生型（Tn 3-Tn 4401嵌合体，CTB）的2倍或更高，并且blaKPC在CTA中表达最高。生物信息学和5′ RACE实验表明，ISKpn 8基因的3′端存在一个新的强启动子PY。PY突变几乎消除了blaKPC的表达（P < 0.01），并恢复了所有3种亚型对碳青霉烯类抗生素的敏感性。尽管PX或P1突变使CTB中blaKPC表达减半（P < 0.05），但PX缺失导致CTA中blaKPC表达增加68%（P = 0.037）。CTC中blaKPC mRNA水平是InCTC中的8倍（P = 0.011），InCTC中含有P1。这些结果表明，PY是blaKPC基因在嵌合体中的核心启动子，PX和P1启动子的缺失分别增强CTA和CTC中的基因表达。
The expression of the blaKPC gene plays a key role in carbapenem resistance in Enterobacteriaceae. However, the genetic regulators of the blaKPC gene have not been completely elucidated, especially the genes in Tn3-Tn4401 chimeras. ABSTRACT The expression of the blaKPC gene plays a key role in carbapenem resistance in Enterobacteriaceae. However, the genetic regulators of the blaKPC gene have not been completely elucidated, especially the genes in Tn3-Tn4401 chimeras. Two novel Tn3-Tn4401 chimera isoforms were characterized in our hospital, isoform A (CTA), which harbors a 121-bp deletion containing the PX promoter and was present in 22.6% (54/239) of isolates, and isoform C (CTC), which harbors a 624-bp insertion and a P1 promoter deletion and was present in only 1 isolate. The carbapenem MICs of both isoforms were 2-fold or more higher than those of the wild type (Tn3-Tn4401 chimera, CTB), and blaKPC was most highly expressed in CTA. Bioinformatics and 5′ rapid amplification of cDNA ends (5′ RACE) experiments indicated a novel strong putative promoter, PY, at the 3′ end of the ISKpn8 gene. PY mutation nearly abrogated blaKPC expression (P < 0.01) and restored carbapenem susceptibility in all 3 isoforms. Although the mutation of PX or P1 halved blaKPC expression in CTB (P < 0.05), PX deletion caused a 68% increase in blaKPC expression (P = 0.037) in CTA. The level of blaKPC mRNA in CTC was 8-fold higher than that in InCTC, which harbors P1 (P = 0.011). These results suggest that PY is a core promoter of the blaKPC gene in the chimeras and that the deletion of the PX and P1 promoters enhanced gene expression in CTA and CTC, respectively.