Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada.
Antimicrob Agents Chemother. 2013 May;57(5):2243-51. doi: 10.1128/AAC.00170-13. Epub 2013 Mar 4.
The amgRS operon encodes a presumed membrane stress-responsive two-component system linked to intrinsic aminoglycoside resistance in Pseudomonas aeruginosa. Genome sequencing of a lab isolate showing modest pan-aminoglycoside resistance, strain K2979, revealed a number of mutations, including a substitution in amgS that produced an R182C change in the AmgS sensor kinase product of this gene. Introduction of this mutation into an otherwise wild-type strain recapitulated the resistance phenotype, while correcting the mutation in the resistant mutant abrogated the resistant phenotype, confirming that the amgS mutation is responsible for the aminoglycoside resistance of strain K2979. The amgSR182 mutation promoted an AmgR-dependent, 2- to 3-fold increase in expression of the AmgRS target genes htpX and PA5528, mirroring the impact of aminoglycoside exposure of wild-type cells on htpX and PA5528 expression. This suggests that amgSR182 is a gain-of-function mutation that activates AmgS and the AmgRS two-component system in promoting modest resistance to aminoglycosides. Screening of several pan-aminoglycoside-resistant clinical isolates of P. aeruginosa revealed three that showed elevated htpX and PA5528 expression and harbored single amino acid-altering mutations in amgS (V121G or D106N) and no mutations in amgR. Introduction of the amgSV121G mutation into wild-type P. aeruginosa generated a resistance phenotype reminiscent of the amgSR182 mutant and produced a 2- to 3-fold increase in htpX and PA5528 expression, confirming that it, too, is a gain-of-function aminoglycoside resistance-promoting mutation. These results highlight the contribution of amgS mutations and activation of the AmgRS two-component system to acquired aminoglycoside resistance in lab and clinical isolates of P. aeruginosa.
amgRS 操纵子编码一个假定的膜应激反应的双组分系统，与铜绿假单胞菌的固有氨基糖苷类抗性有关。对显示适度泛氨基糖苷类抗性的实验室分离株 K2979 的基因组测序揭示了许多突变，包括 amgS 中的取代，导致该基因的 AmgS 传感器激酶产物发生 R182C 变化。将该突变引入其他野生型菌株中可重现抗性表型，而在抗性突变体中纠正该突变则消除了抗性表型，证实 amgS 突变是 K2979 菌株氨基糖苷类抗性的原因。amgSR182 突变促进了 AmgR 依赖性的、2-3 倍的 AmgRS 靶基因 htpX 和 PA5528 的表达增加，反映了野生型细胞暴露于氨基糖苷类药物对 htpX 和 PA5528 表达的影响。这表明 amgSR182 是一种功能获得性突变，可激活 AmgS 和 AmgRS 双组分系统，促进对氨基糖苷类药物的适度抗性。对几种泛氨基糖苷类耐药的铜绿假单胞菌临床分离株进行筛选，发现其中 3 株显示 htpX 和 PA5528 表达升高，并在 amgS 中存在单个氨基酸改变突变（V121G 或 D106N），而 amgR 中没有突变。将 amgSV121G 突变引入野生型铜绿假单胞菌中产生了类似于 amgSR182 突变体的抗性表型，并使 htpX 和 PA5528 的表达增加了 2-3 倍，证实它也是一种功能获得性氨基糖苷类抗性促进突变。这些结果突出了 amgS 突变和 AmgRS 双组分系统的激活对实验室和临床分离株铜绿假单胞菌获得性氨基糖苷类抗性的贡献。
