Morris C M, George A, Wilson W W, Champlin F R
Department of Biological Sciences, Mississippi State University 39762.
J Antibiot (Tokyo). 1995 Jan;48(1):67-72. doi: 10.7164/antibiotics.48.67.
The present study was carried out to determine if sensitization of Gram-negative bacteria to the polyanionic antibiotic daptomycin by cationic molecules can be explained on the basis of decreased cell surface charge in order to better understand intrinsic resistance. Turbidimetric assessments of batch cultural growth kinetics revealed the outer membrane permeabilizer polymyxin B nonapeptide sensitized Pseudomonas aeruginosa and Escherichia coli to the hydrophobic probe novobiocin, whereas little or no sensitization was observed for two surface hydrophobicity variants of Pasteurella multocida. Polymyxin B nonapeptide and daptomycin synergistically inhibited growth of P. aeruginosa only. A hydrocarbon adherence assay revealed permeabilizing concentrations of polymyxin B nonapeptide increased cell surface hydrophobicity of P. aeruginosa and the hydrophobic P. multocida variant, while E. coli and the hydrophilic P. multocida variant remained unaffected. Measurement of cellular electrophoretic mobility showed polymyxin B nonapeptide permeabilization of P. aeruginosa to daptomycin occurred concomitantly with a significant decrease in cell surface charge, while no such sensitization occurred in organisms which failed to undergo polymyxin B nonapeptide-induced surface charge decreases. These data suggest that sensitization of Gram-negative bacteria to polyanionic lipopeptides by growth in the presence of polycationic outer membrane permeabilizers such as polymyxin B nonapeptide is dependent on diminution of overall cell surface charge and polarity, thereby allowing outer cell envelope permeation.
本研究旨在确定阳离子分子使革兰氏阴性菌对多阴离子抗生素达托霉素敏感是否可基于细胞表面电荷减少来解释，以便更好地理解内在抗性。分批培养生长动力学的比浊法评估显示，外膜通透剂多粘菌素B九肽使铜绿假单胞菌和大肠杆菌对疏水探针新生霉素敏感，而多杀巴斯德氏菌的两个表面疏水性变体几乎没有或未观察到敏感性。多粘菌素B九肽和达托霉素仅协同抑制铜绿假单胞菌的生长。烃类黏附试验显示，多粘菌素B九肽的通透浓度增加了铜绿假单胞菌和疏水性多杀巴斯德氏菌变体的细胞表面疏水性，而大肠杆菌和亲水性多杀巴斯德氏菌变体未受影响。细胞电泳迁移率的测量表明，多粘菌素B九肽使铜绿假单胞菌对达托霉素通透的同时，细胞表面电荷显著降低，而在未经历多粘菌素B九肽诱导的表面电荷降低的生物体中未发生这种敏感性。这些数据表明，在多阳离子外膜通透剂（如多粘菌素B九肽）存在下生长，革兰氏阴性菌对多阴离子脂肽的敏感性取决于整体细胞表面电荷和极性的减小，从而允许外细胞膜渗透。
