Evolution of Antibiotic Resistance in Biofilm and Planktonic Pseudomonas aeruginosa Populations Exposed to Subinhibitory Levels of Ciprofloxacin
Evolution of Antibiotic Resistance in Biofilm and Planktonic Pseudomonas aeruginosa Populations Exposed to Subinhibitory Levels of Ciprofloxacin
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DOI：
10.1128/aac.00320-18
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发表时间：
2018-08-01
影响因子：
4.9
通讯作者：
Ciofu, Oana
中科院分区：
文献类型：
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作者：
Ahmed, Marwa N.;Porse, Andreas;Ciofu, Oana
机会性革兰氏阴性病原体铜绿假单胞菌以其固有的和获得性的抗生素耐药性而闻名，它具有形成生物膜的臭名昭著的能力，这通常会促进慢性感染。抗生素耐药性的进化途径主要在浮游生物培养中进行研究，而在生物膜中研究较少。在亚抑制水平（0.1 mg/l）环丙沙星（CIP）的存在下，实验进化了铜绿假单胞菌PAO1菌落生物膜和固定期浮游培养7代，并进行了种群的基因型（全细菌种群测序）和表型评估。我们观察到CIP进化的生物膜群体中CIP抗性的比例高于暴露于相同药物浓度的浮游生物群体。然而，从生物膜菌群中筛选出的cip耐药菌株中环丙沙星的mic低于从浮游培养中筛选出的cip耐药菌株的mic。我们发现了不同谱系之间共同的进化轨迹，包括已知CIP抗性决定因素的突变以及生长条件依赖的适应性。我们观察到在cip进化的群体中，iv型菌毛依赖的运动（抽搐）减少的总体趋势，以及在缺乏抗生素的情况下进化的群体中毒力相关性状的丧失。总之，我们的数据表明，生物膜促进了低水平突变耐药性的发展，这可能是由于与浮游培养相比，生物膜的有效药物暴露更低。这些结果为两种不同生长条件下抗性变异的选择过程及其进化机制提供了一个框架。
The opportunistic Gram-negative pathogen Pseudomonas aeruginosa, known for its intrinsic and acquired antibiotic resistance, has a notorious ability to form biofilms, which often facilitate chronic infections. The evolutionary paths to antibiotic resistance have mainly been investigated in planktonic cultures and are less studied in biofilms. We experimentally evolved P. aeruginosa PAO1 colony biofilms and stationary-phase planktonic cultures for seven passages in the presence of sub-inhibitory levels (0.1 mg/liter) of ciprofloxacin (CIP) and performed a genotypic (whole-bacterial population sequencing) and phenotypic assessment of the populations. We observed a higher proportion of CIP resistance in the CIP-evolved biofilm populations than in planktonic populations exposed to the same drug concentrations. However, the MICs of ciprofloxacin were lower in CIP-resistant isolates selected from the biofilm population than the MICs of CIP-resistant isolates from the planktonic cultures. We found common evolutionary trajectories between the different lineages, with mutations in known CIP resistance determinants as well as growth condition-dependent adaptations. We observed a general trend toward a reduction in type IV-pilus-dependent motility (twitching) in CIP-evolved populations and a loss of virulence-associated traits in the populations evolved in the absence of antibiotic. In conclusion, our data indicate that biofilms facilitate the development of low-level mutational resistance, probably due to the lower effective drug exposure than in planktonic cultures. These results provide a framework for the selection process of resistant variants and the evolutionary mechanisms involved under the two different growth conditions.