Valcourt Chantal, Buyck Julien M, Grégoire Nicolas, Couet William, Marchand Sandrine, Tewes Frédéric
INSERM U1070 "Pharmacology of Anti-Infective Agents", 1 rue Georges Bonnet, Pôle Biologie Santé, 86022 Poitiers, France.
UFR Médecine-Pharmacie Université de Poitiers, 6 rue de la Milétrie, TSA 51115, 86073 Poitiers, France.
Pharmaceutics. 2021 Nov 3;13(11):1849. doi: 10.3390/pharmaceutics13111849.
Resistance to colistin, one of the antibiotics of last resort against multidrug-resistant Gram-negative bacteria, is increasingly reported. Notably, MCR plasmids discovered in 2015 have now been reported worldwide in humans. To keep this antibiotic of last resort efficient, a way to tackle this mechanism seems essential. Terpene alcohols such as farnesol have been shown to improve the efficacy of some antibiotics. However, their high lipophilicity makes them difficult to use. This problem can be solved by encapsulating them in water-dispersible lipid nanoparticles (LNPs). The aim of this study was to discover, using checkerboard tests and time-kill curve experiments, an association between colistin and farnesol or geraniol loaded in LNPs, which would improve the efficacy of colistin against and, in particular, MCR-1 transconjugants. Then, the effect of the combination on inner membrane permeabilisation was evaluated using propidium iodide (PI) uptake and compared to human red blood cells plasma membrane permeabilisation. Both terpene alcohols were able to restore the susceptibility of J53 MCR-1 to colistin with the same efficacy (E = 16, i.e., colistin MIC was decreased from 8 to 0.5 mg/L). However, with an EC of 2.69 mg/L, farnesol was more potent than geraniol (EC = 39.49 mg/L). Time-kill studies showed a bactericidal effect on MCR-1 transconjugant 6 h after incubation, with no regrowth up to 30 h in the presence of 1 mg/L colistin (1/8 MIC) and 60 mg/L or 200 mg/L farnesol or geraniol, respectively. Colistin alone was more potent in increasing PI uptake rate in the susceptible strain (EC = 0.86 ± 0.08 mg/L) than in the MCR-1 one (EC = 7.38 ± 0.85 mg/L). Against the MCR-1 strain, farnesol-loaded LNP at 60 mg/L enhanced the colistin-induced inner membrane permeabilization effect up to 5-fold and also increased its potency as shown by the decrease in its EC from 7.38 ± 0.85 mg/L to 2.69 ± 0.25 mg/L. Importantly, no hemolysis was observed for LNPs loaded with farnesol or geraniol, alone or in combination with colistin, at the concentrations showing the maximum decrease in colistin MICs. The results presented here indicate that farnesol-loaded LNPs should be studied as combination therapy with colistin to prevent the development of resistance to this antibiotic of last resort.
对黏菌素（一种针对多重耐药革兰氏阴性菌的最后一道防线抗生素）的耐药性报道日益增多。值得注意的是，2015年发现的MCR质粒现已在全球范围内的人类中被报道。为了使这种最后一道防线的抗生素保持有效，解决这一耐药机制的方法似乎至关重要。诸如法尼醇等萜烯醇已被证明可提高某些抗生素的疗效。然而，它们的高亲脂性使其难以使用。这个问题可以通过将它们封装在水分散性脂质纳米颗粒（LNPs）中来解决。本研究的目的是通过棋盘格试验和时间杀菌曲线实验，发现载于LNPs中的黏菌素与法尼醇或香叶醇之间的协同作用，这将提高黏菌素对特别是MCR - 1转接合子的疗效。然后，使用碘化丙啶（PI）摄取评估该组合对内膜通透性的影响，并与人类红细胞质膜通透性进行比较。两种萜烯醇都能够以相同的疗效（E = 16，即黏菌素的MIC从8mg/L降至0.5mg/L）恢复J53 MCR - 1对黏菌素 的敏感性。然而，法尼醇的效力更强，其EC为2.69mg/L，而香叶醇的EC为39.49mg/L。时间杀菌研究表明，孵育6小时后对MCR - 1转接合子有杀菌作用，在存在1mg/L黏菌素（1/8 MIC）和60mg/L或200mg/L法尼醇或香叶醇的情况下，直至30小时都没有再生长。单独使用黏菌素时，在敏感菌株中提高PI摄取率的效力（EC = 0.86±0.08mg/L）高于MCR - 1菌株（EC = 7.38±0.85mg/L）。对于MCR - 1菌株，60mg/L载有法尼醇的LNP将黏菌素诱导的内膜通透性增强作用提高了5倍，并且还提高了其效力，表现为其EC从7.38±0.85mg/L降至2.69±0.25mg/L。重要的是，在显示黏菌素MIC最大降低的浓度下，单独或与黏菌素组合的载有法尼醇或香叶醇的LNPs均未观察到溶血现象。此处呈现的结果表明，载有法尼醇的LNPs应作为与黏菌素的联合疗法进行研究，以防止对这种最后一道防线抗生素产生耐药性。
