Cardiff School of Biosciences, Cardiff University, Cardiff, Wales, CF10 3AT, UK.
BMC Genomics. 2011 Jul 22;12:373. doi: 10.1186/1471-2164-12-373.
Burkholderia cenocepacia is a member of the Burkholderia cepacia complex group of bacteria that cause infections in individuals with cystic fibrosis. B. cenocepacia isolate J2315 has been genome sequenced and is representative of a virulent, epidemic CF strain (ET12). Its genome encodes multiple antimicrobial resistance pathways and it is not known which of these is important for intrinsic or spontaneous resistance. To map these pathways, transcriptomic analysis was performed on: (i) strain J2315 exposed to sub-inhibitory concentrations of antibiotics and the antibiotic potentiator chlorpromazine, and (ii) on spontaneous mutants derived from J2315 and with increased resistance to the antibiotics amikacin, meropenem and trimethoprim-sulfamethoxazole. Two pan-resistant ET12 outbreak isolates recovered two decades after J2315 were also compared to identify naturally evolved gene expression changes.
Spontaneous resistance in B. cenocepacia involved more gene expression changes and different subsets of genes than those provoked by exposure to sub inhibitory concentrations of each antibiotic. The phenotype and altered gene expression in the resistant mutants was also stable irrespective of the presence of the priming antibiotic. Both known and novel genes involved in efflux, antibiotic degradation/modification, membrane function, regulation and unknown functions were mapped. A novel role for the phenylacetic acid (PA) degradation pathway genes was identified in relation to spontaneous resistance to meropenem and glucose was found to repress their expression. Subsequently, 20 mM glucose was found to produce greater that 2-fold reductions in the MIC of multiple antibiotics against B. cenocepacia J2315. Mutation of an RND multidrug efflux pump locus (BCAM0925-27) and squalene-hopene cyclase gene (BCAS0167), both upregulated after chlorpromazine exposure, confirmed their role in resistance. The recently isolated outbreak isolates had altered the expression of multiple genes which mirrored changes seen in the antibiotic resistant mutants, corroborating the strategy used to model resistance. Mutation of an ABC transporter gene (BCAS0081) upregulated in both outbreak strains, confirmed its role in B. cenocepacia resistance.
Global mapping of the genetic pathways which mediate antibiotic resistance in B. cenocepacia has revealed that they are multifactorial, identified potential therapeutic targets and also demonstrated that putative catabolite repression of genes by glucose can improve antibiotic efficacy.
洋葱伯克霍尔德菌是洋葱伯克霍尔德菌群的成员，可引起囊性纤维化患者的感染。B. cenocepacia 分离株 J2315 已完成基因组测序，是一种具有毒力的流行 CF 菌株（ET12）的代表。其基因组编码多种抗生素耐药途径，尚不清楚这些途径中的哪一种对固有或自发耐药性很重要。为了绘制这些途径，对以下方面进行了转录组分析：（i）暴露于亚抑制浓度抗生素和抗生素增效剂氯丙嗪的菌株 J2315，以及（ii）源自 J2315 并对抗生素阿米卡星、美罗培南和磺胺甲恶唑-甲氧苄啶的耐药性增加的自发突变体。对 20 年前从 J2315 分离出的两种泛耐药 ET12 暴发分离株进行了比较，以鉴定自然进化的基因表达变化。
与暴露于每种抗生素的亚抑制浓度相比，B. cenocepacia 的自发耐药涉及更多的基因表达变化和不同的基因亚群。耐药突变体的表型和改变的基因表达在没有诱导抗生素的情况下也是稳定的。涉及外排、抗生素降解/修饰、膜功能、调节和未知功能的已知和新型基因都被定位。在与美罗培南自发耐药相关的苯乙酸（PA）降解途径基因中发现了一个新的作用，发现葡萄糖抑制其表达。随后发现，20 mM 葡萄糖可使 B. cenocepacia J2315 对多种抗生素的 MIC 降低 2 倍以上。突变 RND 多药外排泵基因座（BCAM0925-27）和角鲨烯-法呢烯环化酶基因（BCAS0167），这两个基因在氯丙嗪暴露后均上调，证实了它们在耐药中的作用。最近分离的暴发分离株改变了多个基因的表达，这些变化与抗生素耐药突变体所见的变化相吻合，证实了用于模拟耐药性的策略。在两个暴发株中均上调的 ABC 转运基因（BCAS0081）的突变证实了其在 B. cenocepacia 耐药性中的作用。
对洋葱伯克霍尔德菌介导抗生素耐药性的遗传途径进行全局映射揭示了它们是多因素的，确定了潜在的治疗靶点，并证明了葡萄糖对基因的潜在代谢物抑制作用可提高抗生素的疗效。
