Lee Ji-Young, Chung Eun Seon, Na In Young, Kim Hyunkeun, Shin Dongwoo, Ko Kwan Soo
Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, South Korea.
Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, South Korea
J Antimicrob Chemother. 2014 Nov;69(11):2966-71. doi: 10.1093/jac/dku238. Epub 2014 Jul 2.
Colistin susceptibility in Pseudomonas aeruginosa is associated with a lipopolysaccharide (LPS) structure that is controlled by the modulation of several two-component regulatory systems. In this study, we attempted to elucidate the role of these two-component systems in the development of colistin resistance in P. aeruginosa.
pmrA-, phoP-, parR- or cprR-inactivated mutants were constructed from a colistin-susceptible P5 strain. Colistin-resistant mutants (P5R, P5ΔpmrA-R, P5ΔphoP-R, P5ΔparR-R and P5ΔcprR-R) were developed in vitro from a wild-type strain (P5) and pmrA-, phoP-, parR- or cprR-inactivated mutants by serial passage in colistin-containing media. Expression levels of the pmrA, phoP, parR, cprR and arnB genes were determined and amino acid alterations of two-component regulatory systems during development of colistin resistance were also investigated.
While P5ΔpmrA-R, P5ΔparR-R and P5ΔcprR-R showed elevated expression of the phoP gene, the expression levels of the pmrA, parR and cprR genes were not different between gene-inactivated mutants and the adapted colistin-resistant mutants. P5ΔphoP-R showed no significant elevation in expression of any of the pmrA, parR or cprR genes. The arnB gene was overexpressed in all in vitro-selected colistin-resistant mutants compared with colistin-susceptible wild-type and gene-inactivated mutants. Three amino acid alterations in PhoQ and three in ParS were identified in induced colistin-resistant mutants.
Our data suggest that individual two-component systems may not be essential for the acquisition of colistin resistance in P. aeruginosa. The PhoPQ two-component system may play a major role in the development of colistin resistance in our strains, but alternative or compensatory pathways may exist.
铜绿假单胞菌对黏菌素的敏感性与脂多糖（LPS）结构有关，该结构受多种双组分调节系统的调控。在本研究中，我们试图阐明这些双组分系统在铜绿假单胞菌黏菌素耐药性形成中的作用。
从对黏菌素敏感的P5菌株构建pmrA、phoP、parR或cprR基因失活的突变体。通过在含黏菌素的培养基中连续传代，从野生型菌株（P5）以及pmrA、phoP、parR或cprR基因失活的突变体中体外诱导出黏菌素耐药突变体（P5R、P5ΔpmrA-R、P5ΔphoP-R、P5ΔparR-R和P5ΔcprR-R）。测定pmrA、phoP、parR、cprR和arnB基因的表达水平，并研究黏菌素耐药性形成过程中双组分调节系统的氨基酸变化。
虽然P5ΔpmrA-R、P5ΔparR-R和P5ΔcprR-R中phoP基因表达升高，但基因失活突变体与适应性黏菌素耐药突变体之间pmrA、parR和cprR基因的表达水平没有差异。P5ΔphoP-R中pmrA、parR或cprR基因的表达均未显著升高。与黏菌素敏感的野生型和基因失活突变体相比，arnB基因在所有体外筛选的黏菌素耐药突变体中均过表达。在诱导的黏菌素耐药突变体中鉴定出PhoQ的三个氨基酸变化和ParS的三个氨基酸变化。
我们的数据表明，单个双组分系统对于铜绿假单胞菌获得黏菌素耐药性可能不是必需的。PhoPQ双组分系统可能在我们的菌株中黏菌素耐药性形成中起主要作用，但可能存在替代或补偿途径。
