Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, United States of America.
Department of Virology and Microbiology, Baylor College of Medicine, Houston, Texas, United States of America.
PLoS One. 2019 Jan 11;14(1):e0210547. doi: 10.1371/journal.pone.0210547. eCollection 2019.
New antibiotics are needed against antibiotic-resistant gram-negative bacteria. The repurposed antifungal drug, ciclopirox, equally blocks antibiotic-susceptible or multidrug-resistant Acinetobacter baumannii, Escherichia coli, and Klebsiella pneumoniae clinical isolates, indicating that it is not affected by existing resistance mechanisms. Toward understanding how ciclopirox blocks growth, we screened E. coli mutant strains and found that disruption of genes encoding products involved in galactose salvage, enterobacterial common antigen synthesis, and transport of the iron binding siderophore, enterobactin, lowered the minimum inhibitory concentration of ciclopirox needed to block growth of the mutant compared to the isogenic parent strain. We found that ciclopirox induced enterobactin production and that this effect is strongly affected by the deletion of the galactose salvage genes encoding UDP-galactose 4-epimerase, galE, or galactose-1-phosphate uridylyltransferase, galT. As disruption of ECA synthesis activates the regulation of capsular synthesis (Rcs) phosphorelay, which inhibits bacterial swarming and promotes biofilm development, we test whether ciclopirox prevents activation of the Rcs pathway. Sub-inhibitory concentrations of ciclopirox increased swarming of the E. coli laboratory K12 strain BW25113 but had widely varying effects on swarming or surface motility of clinical isolate E. coli, A. baumannii, and K. pneumoniae. There was no effect of ciclopirox on biofilm production, suggesting it does not target Rcs. Altogether, our data suggest ciclopirox-mediated alteration of lipopolysaccharides stimulates enterobactin production and affects bacterial swarming.
需要新的抗生素来对抗对抗生素具有耐药性的革兰氏阴性菌。重新利用的抗真菌药物环吡酮同样可以阻止抗生素敏感或多药耐药的鲍曼不动杆菌、大肠杆菌和肺炎克雷伯菌临床分离株的生长，这表明它不受现有耐药机制的影响。为了了解环吡酮如何阻止细菌生长，我们筛选了大肠杆菌突变菌株，发现编码参与半乳糖回收、肠杆菌共同抗原合成以及铁结合铁载体enterobactin 转运的基因产物的基因缺失，会降低环吡酮抑制突变株生长所需的最小抑菌浓度，与同基因亲本菌株相比。我们发现环吡酮诱导 enterobactin 的产生，并且这种作用强烈受到半乳糖回收基因编码 UDP-半乳糖 4-差向异构酶、galE 或半乳糖-1-磷酸尿苷酰转移酶、galT 的缺失的影响。由于 ECA 合成的破坏激活了调节荚膜合成（Rcs）磷酸传递系统，这会抑制细菌的群集运动并促进生物膜的发展，因此我们测试了环吡酮是否可以防止 Rcs 途径的激活。亚抑制浓度的环吡酮增加了大肠杆菌实验室 K12 菌株 BW25113 的群集运动，但对临床分离株大肠杆菌、鲍曼不动杆菌和肺炎克雷伯菌的群集或表面运动的影响差异很大。环吡酮对生物膜的产生没有影响，这表明它不是针对 Rcs 的。总的来说，我们的数据表明，环吡酮介导的脂多糖改变刺激了 enterobactin 的产生，并影响了细菌的群集运动。
