Department of Molecular Genetics, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA.
Department of Biological Sciences, College of Arts and Sciences, Florida International University, Miami, FL, USA.
J Med Microbiol. 2014 Apr;63(Pt 4):544-555. doi: 10.1099/jmm.0.070185-0. Epub 2014 Jan 25.
Pseudomonas aeruginosa is one of the most dreaded opportunistic pathogens accounting for 10 % of hospital-acquired infections, with a 50 % mortality rate in chronically ill patients. The increased prevalence of drug-resistant isolates is a major cause of concern. Resistance in P. aeruginosa is mediated by various mechanisms, some of which are shared among different classes of antibiotics and which raise the possibility of cross-resistance. The goal of this study was to explore the effect of subinhibitory concentrations (SICs) of clinically relevant antibiotics and the role of a global antibiotic resistance and virulence regulator, AmpR, in developing cross-resistance. We investigated the induction of transient cross-resistance in P. aeruginosa PAO1 upon exposure to SICs of antibiotics. Pre-exposure to carbapenems, specifically imipenem, even at 3 ng ml(-1), adversely affected the efficacy of clinically used penicillins and cephalosporins. The high β-lactam resistance was due to elevated expression of both ampC and ampR, encoding a chromosomal β-lactamase and its regulator, respectively. Differences in the susceptibility of ampR and ampC mutants suggested non-AmpC-mediated regulation of β-lactam resistance by AmpR. The increased susceptibility of P. aeruginosa in the absence of ampR to various antibiotics upon SIC exposure suggests that AmpR plays a major role in the cross-resistance. AmpR was shown previously to be involved in resistance to quinolones by regulating MexEF-OprN efflux pump. The data here further indicate the role of AmpR in cross-resistance between quinolones and aminoglycosides. This was confirmed using quantitative PCR, where expression of the mexEF efflux pump was further induced by ciprofloxacin and tobramycin, its substrate and a non-substrate, respectively, in the absence of ampR. The data presented here highlight the intricate cross-regulation of antibiotic resistance pathways at SICs of antibiotics and the need for careful assessment of the order of antibiotic regimens as this may have dire consequences. Targeting a global regulator such as AmpR that connects diverse pathways is a feasible therapeutic approach to combat P. aeruginosa pathogenesis.
铜绿假单胞菌是最令人恐惧的机会性病原体之一，占医院获得性感染的 10%，在慢性疾病患者中的死亡率为 50%。耐药分离株的增加是一个主要的关注原因。铜绿假单胞菌的耐药性是由多种机制介导的，其中一些机制在不同类别的抗生素之间共享，并增加了交叉耐药的可能性。本研究的目的是探讨临床相关抗生素的亚抑菌浓度（SIC）和全局抗生素耐药性和毒力调节剂 AmpR 在产生交叉耐药性方面的作用。我们研究了铜绿假单胞菌 PAO1 暴露于抗生素 SIC 时诱导短暂交叉耐药的情况。预先接触碳青霉烯类抗生素，特别是亚胺培南，即使浓度低至 3ng/ml，也会对临床使用的青霉素类和头孢菌素类药物的疗效产生不利影响。高β-内酰胺耐药性是由于 AmpC 和 AmpR 的表达均升高所致，AmpC 和 AmpR 分别编码染色体β-内酰胺酶及其调节剂。AmpR 和 AmpC 突变体的敏感性差异表明 AmpR 通过非 AmpC 机制调节β-内酰胺耐药性。在 SIC 暴露下，缺乏 AmpR 的铜绿假单胞菌对各种抗生素的敏感性增加表明 AmpR 在交叉耐药中起主要作用。先前的研究表明，AmpR 通过调节 MexEF-OprN 外排泵参与喹诺酮类药物的耐药性。这里的数据进一步表明 AmpR 在喹诺酮类药物和氨基糖苷类药物之间的交叉耐药中的作用。这通过定量 PCR 得到证实，在没有 AmpR 的情况下，环丙沙星和妥布霉素（其底物和非底物）分别进一步诱导 MexEF 外排泵的表达。这里提出的研究结果强调了抗生素 SIC 下抗生素耐药途径的复杂交叉调控，以及需要仔细评估抗生素方案的顺序，因为这可能会产生严重后果。针对 AmpR 等连接多种途径的全局调节剂是对抗铜绿假单胞菌发病机制的可行治疗方法。
