Objectives To determine the activity of murepavadin in comparison with tobramycin, colistin and aztreonam, against cystic fibrosis (CF) Pseudomonas aeruginosa isolates growing in biofilms. The biofilm-epidemiological cut-off (ECOFF) values that include intrinsic resistance mechanisms present in biofilms were estimated. Methods Fifty-three CF P. aeruginosa isolates from respiratory samples were tested using the Calgary (closed system) device, while 4 [2 clinical (one smooth, one mucoid) and 2 reference strains] were tested using the BioFlux, a microfluidic open model of biofilm testing. Biofilm was stained with SYTO9® and propidium iodide. The minimal biofilm inhibitory concentration (MBIC) and the minimal biofilm eradication concentration (MBEC) were determined. The MBIC-ECOFF and the MBEC-ECOFF were calculated. Results Colistin, tobramycin and murepavadin presented similar MBIC50/MBIC90 values (4/32, 8/64 and 2/32, respectively). Murepavadin exhibited the lowest MBEC90 (64 mg/L). Aztreonam MBIC and MBEC values were higher than those of the other antibiotics tested. Tobramycin and murepavadin had the lowest MBEC-ECOFF (64 and 128 mg/L, respectively), while those of aztreonam and colistin exceeded 512 mg/L. Using the BioFlux, for the PAO1, PAO mutS and the smooth clinical strain, a significant difference (P < 0.0125) was observed when comparing the fluorescence of treated and untreated biofilms. For the mucoid strain, only the biofilm treated with aztreonam (MBIC and MBEC) and tobramycin (MBEC) showed differences with respect to the untreated biofilm. Conclusions Murepavadin demonstrated good activity against P. aeruginosa biofilms both in open and closed systems. The MBIC-ECOFF and the MBEC-ECOFF are proposed as new parameters to estimate the activity of antibiotics on biofilms.

中文翻译：

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murepavadin对囊性纤维化铜绿假单胞菌分离株的抗生物膜活性

目的 确定 murepavadin 与妥布霉素、粘菌素和氨曲南相比对生物膜中生长的铜绿假单胞菌分离株囊性纤维化 (CF) 的活性。估计了包括生物膜中存在的内在抗性机制的生物膜流行病学截止值 (ECOFF)。方法 使用 Calgary（封闭系统）装置检测来自呼吸道样本的 53 株 CF P.aeruginosa 分离株，而使用微流体开放模型 BioFlux 检测 4 株[2 种临床（1 株光滑，1 株粘液）和 2 种参考菌株]生物膜测试。生物膜用 SYTO9® 和碘化丙锭染色。测定最小生物膜抑制浓度（MBIC）和最小生物膜清除浓度（MBEC）。计算 MBIC-ECOFF 和 MBEC-ECOFF。结果粘菌素，妥布霉素和 murepavadin 呈现出相似的 MBIC50/MBIC90 值（分别为 4/32、8/64 和 2/32）。Murepavadin 表现出最低的 MBEC90 (64 mg/L)。氨曲南 MBIC 和 MBEC 值高于其他测试的抗生素。妥布霉素和 murepavadin 的 MBEC-ECOFF 最低（分别为 64 和 128 mg/L），而氨曲南和多粘菌素超过 512 mg/L。使用 BioFlux，对于 PAO1、PAO mutS 和平滑临床菌株，在比较处理和未处理的生物膜的荧光时观察到显着差异 (P < 0.0125)。对于粘液菌株，只有用氨曲南（MBIC 和 MBEC）和妥布霉素（MBEC）处理的生物膜与未处理的生物膜有差异。结论 Murepavadin 在开放和封闭系统中均表现出对铜绿假单胞菌生物膜的良好活性。